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Message-ID: <20250228093024.114983-13-Neeraj.Upadhyay@amd.com>
Date: Fri, 28 Feb 2025 15:00:05 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: <kvm@...r.kernel.org>, <seanjc@...gle.com>, <pbonzini@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <Thomas.Lendacky@....com>,
<nikunj@....com>, <Santosh.Shukla@....com>, <Vasant.Hegde@....com>,
<Suravee.Suthikulpanit@....com>, <bp@...en8.de>, <David.Kaplan@....com>,
<huibo.wang@....com>, <naveen.rao@....com>, <pgonda@...gle.com>,
<linux-kselftest@...r.kernel.org>, <shuah@...nel.org>
Subject: [RFC PATCH 12/31] KVM: selftests: Add instruction decoding support
Add instruction deconding support for MMIO instruction
decoding in SEV-ES VC handler path. For ease of review,
file insn-eval.c is a snapshot of the file from arch/x86/lib/.
It will be updated in subsequent commits with the modifications
to just support minimal instruction deconding.
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
---
tools/testing/selftests/kvm/.gitignore | 3 +-
.../testing/selftests/kvm/lib/x86/insn-eval.c | 1670 +++++++++++++++++
2 files changed, 1672 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/kvm/lib/x86/insn-eval.c
diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
index 1d41a046a7bf..7f75c8a2f722 100644
--- a/tools/testing/selftests/kvm/.gitignore
+++ b/tools/testing/selftests/kvm/.gitignore
@@ -9,4 +9,5 @@
!config
!settings
!Makefile
-!Makefile.kvm
\ No newline at end of file
+!Makefile.kvm
+
diff --git a/tools/testing/selftests/kvm/lib/x86/insn-eval.c b/tools/testing/selftests/kvm/lib/x86/insn-eval.c
new file mode 100644
index 000000000000..98631c0e7a11
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/x86/insn-eval.c
@@ -0,0 +1,1670 @@
+/*
+ * Utility functions for x86 operand and address decoding
+ *
+ * Copyright (C) Intel Corporation 2017
+ */
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/ratelimit.h>
+#include <linux/mmu_context.h>
+#include <asm/desc_defs.h>
+#include <asm/desc.h>
+#include <asm/inat.h>
+#include <asm/insn.h>
+#include <asm/insn-eval.h>
+#include <asm/ldt.h>
+#include <asm/vm86.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt) "insn: " fmt
+
+enum reg_type {
+ REG_TYPE_RM = 0,
+ REG_TYPE_REG,
+ REG_TYPE_INDEX,
+ REG_TYPE_BASE,
+};
+
+/**
+ * is_string_insn() - Determine if instruction is a string instruction
+ * @insn: Instruction containing the opcode to inspect
+ *
+ * Returns:
+ *
+ * true if the instruction, determined by the opcode, is any of the
+ * string instructions as defined in the Intel Software Development manual.
+ * False otherwise.
+ */
+static bool is_string_insn(struct insn *insn)
+{
+ /* All string instructions have a 1-byte opcode. */
+ if (insn->opcode.nbytes != 1)
+ return false;
+
+ switch (insn->opcode.bytes[0]) {
+ case 0x6c ... 0x6f: /* INS, OUTS */
+ case 0xa4 ... 0xa7: /* MOVS, CMPS */
+ case 0xaa ... 0xaf: /* STOS, LODS, SCAS */
+ return true;
+ default:
+ return false;
+ }
+}
+
+/**
+ * insn_has_rep_prefix() - Determine if instruction has a REP prefix
+ * @insn: Instruction containing the prefix to inspect
+ *
+ * Returns:
+ *
+ * true if the instruction has a REP prefix, false if not.
+ */
+bool insn_has_rep_prefix(struct insn *insn)
+{
+ insn_byte_t p;
+ int i;
+
+ insn_get_prefixes(insn);
+
+ for_each_insn_prefix(insn, i, p) {
+ if (p == 0xf2 || p == 0xf3)
+ return true;
+ }
+
+ return false;
+}
+
+/**
+ * get_seg_reg_override_idx() - obtain segment register override index
+ * @insn: Valid instruction with segment override prefixes
+ *
+ * Inspect the instruction prefixes in @insn and find segment overrides, if any.
+ *
+ * Returns:
+ *
+ * A constant identifying the segment register to use, among CS, SS, DS,
+ * ES, FS, or GS. INAT_SEG_REG_DEFAULT is returned if no segment override
+ * prefixes were found.
+ *
+ * -EINVAL in case of error.
+ */
+static int get_seg_reg_override_idx(struct insn *insn)
+{
+ int idx = INAT_SEG_REG_DEFAULT;
+ int num_overrides = 0, i;
+ insn_byte_t p;
+
+ insn_get_prefixes(insn);
+
+ /* Look for any segment override prefixes. */
+ for_each_insn_prefix(insn, i, p) {
+ insn_attr_t attr;
+
+ attr = inat_get_opcode_attribute(p);
+ switch (attr) {
+ case INAT_MAKE_PREFIX(INAT_PFX_CS):
+ idx = INAT_SEG_REG_CS;
+ num_overrides++;
+ break;
+ case INAT_MAKE_PREFIX(INAT_PFX_SS):
+ idx = INAT_SEG_REG_SS;
+ num_overrides++;
+ break;
+ case INAT_MAKE_PREFIX(INAT_PFX_DS):
+ idx = INAT_SEG_REG_DS;
+ num_overrides++;
+ break;
+ case INAT_MAKE_PREFIX(INAT_PFX_ES):
+ idx = INAT_SEG_REG_ES;
+ num_overrides++;
+ break;
+ case INAT_MAKE_PREFIX(INAT_PFX_FS):
+ idx = INAT_SEG_REG_FS;
+ num_overrides++;
+ break;
+ case INAT_MAKE_PREFIX(INAT_PFX_GS):
+ idx = INAT_SEG_REG_GS;
+ num_overrides++;
+ break;
+ /* No default action needed. */
+ }
+ }
+
+ /* More than one segment override prefix leads to undefined behavior. */
+ if (num_overrides > 1)
+ return -EINVAL;
+
+ return idx;
+}
+
+/**
+ * check_seg_overrides() - check if segment override prefixes are allowed
+ * @insn: Valid instruction with segment override prefixes
+ * @regoff: Operand offset, in pt_regs, for which the check is performed
+ *
+ * For a particular register used in register-indirect addressing, determine if
+ * segment override prefixes can be used. Specifically, no overrides are allowed
+ * for rDI if used with a string instruction.
+ *
+ * Returns:
+ *
+ * True if segment override prefixes can be used with the register indicated
+ * in @regoff. False if otherwise.
+ */
+static bool check_seg_overrides(struct insn *insn, int regoff)
+{
+ if (regoff == offsetof(struct pt_regs, di) && is_string_insn(insn))
+ return false;
+
+ return true;
+}
+
+/**
+ * resolve_default_seg() - resolve default segment register index for an operand
+ * @insn: Instruction with opcode and address size. Must be valid.
+ * @regs: Register values as seen when entering kernel mode
+ * @off: Operand offset, in pt_regs, for which resolution is needed
+ *
+ * Resolve the default segment register index associated with the instruction
+ * operand register indicated by @off. Such index is resolved based on defaults
+ * described in the Intel Software Development Manual.
+ *
+ * Returns:
+ *
+ * If in protected mode, a constant identifying the segment register to use,
+ * among CS, SS, ES or DS. If in long mode, INAT_SEG_REG_IGNORE.
+ *
+ * -EINVAL in case of error.
+ */
+static int resolve_default_seg(struct insn *insn, struct pt_regs *regs, int off)
+{
+ if (any_64bit_mode(regs))
+ return INAT_SEG_REG_IGNORE;
+ /*
+ * Resolve the default segment register as described in Section 3.7.4
+ * of the Intel Software Development Manual Vol. 1:
+ *
+ * + DS for all references involving r[ABCD]X, and rSI.
+ * + If used in a string instruction, ES for rDI. Otherwise, DS.
+ * + AX, CX and DX are not valid register operands in 16-bit address
+ * encodings but are valid for 32-bit and 64-bit encodings.
+ * + -EDOM is reserved to identify for cases in which no register
+ * is used (i.e., displacement-only addressing). Use DS.
+ * + SS for rSP or rBP.
+ * + CS for rIP.
+ */
+
+ switch (off) {
+ case offsetof(struct pt_regs, ax):
+ case offsetof(struct pt_regs, cx):
+ case offsetof(struct pt_regs, dx):
+ /* Need insn to verify address size. */
+ if (insn->addr_bytes == 2)
+ return -EINVAL;
+
+ fallthrough;
+
+ case -EDOM:
+ case offsetof(struct pt_regs, bx):
+ case offsetof(struct pt_regs, si):
+ return INAT_SEG_REG_DS;
+
+ case offsetof(struct pt_regs, di):
+ if (is_string_insn(insn))
+ return INAT_SEG_REG_ES;
+ return INAT_SEG_REG_DS;
+
+ case offsetof(struct pt_regs, bp):
+ case offsetof(struct pt_regs, sp):
+ return INAT_SEG_REG_SS;
+
+ case offsetof(struct pt_regs, ip):
+ return INAT_SEG_REG_CS;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+/**
+ * resolve_seg_reg() - obtain segment register index
+ * @insn: Instruction with operands
+ * @regs: Register values as seen when entering kernel mode
+ * @regoff: Operand offset, in pt_regs, used to determine segment register
+ *
+ * Determine the segment register associated with the operands and, if
+ * applicable, prefixes and the instruction pointed by @insn.
+ *
+ * The segment register associated to an operand used in register-indirect
+ * addressing depends on:
+ *
+ * a) Whether running in long mode (in such a case segments are ignored, except
+ * if FS or GS are used).
+ *
+ * b) Whether segment override prefixes can be used. Certain instructions and
+ * registers do not allow override prefixes.
+ *
+ * c) Whether segment overrides prefixes are found in the instruction prefixes.
+ *
+ * d) If there are not segment override prefixes or they cannot be used, the
+ * default segment register associated with the operand register is used.
+ *
+ * The function checks first if segment override prefixes can be used with the
+ * operand indicated by @regoff. If allowed, obtain such overridden segment
+ * register index. Lastly, if not prefixes were found or cannot be used, resolve
+ * the segment register index to use based on the defaults described in the
+ * Intel documentation. In long mode, all segment register indexes will be
+ * ignored, except if overrides were found for FS or GS. All these operations
+ * are done using helper functions.
+ *
+ * The operand register, @regoff, is represented as the offset from the base of
+ * pt_regs.
+ *
+ * As stated, the main use of this function is to determine the segment register
+ * index based on the instruction, its operands and prefixes. Hence, @insn
+ * must be valid. However, if @regoff indicates rIP, we don't need to inspect
+ * @insn at all as in this case CS is used in all cases. This case is checked
+ * before proceeding further.
+ *
+ * Please note that this function does not return the value in the segment
+ * register (i.e., the segment selector) but our defined index. The segment
+ * selector needs to be obtained using get_segment_selector() and passing the
+ * segment register index resolved by this function.
+ *
+ * Returns:
+ *
+ * An index identifying the segment register to use, among CS, SS, DS,
+ * ES, FS, or GS. INAT_SEG_REG_IGNORE is returned if running in long mode.
+ *
+ * -EINVAL in case of error.
+ */
+static int resolve_seg_reg(struct insn *insn, struct pt_regs *regs, int regoff)
+{
+ int idx;
+
+ /*
+ * In the unlikely event of having to resolve the segment register
+ * index for rIP, do it first. Segment override prefixes should not
+ * be used. Hence, it is not necessary to inspect the instruction,
+ * which may be invalid at this point.
+ */
+ if (regoff == offsetof(struct pt_regs, ip)) {
+ if (any_64bit_mode(regs))
+ return INAT_SEG_REG_IGNORE;
+ else
+ return INAT_SEG_REG_CS;
+ }
+
+ if (!insn)
+ return -EINVAL;
+
+ if (!check_seg_overrides(insn, regoff))
+ return resolve_default_seg(insn, regs, regoff);
+
+ idx = get_seg_reg_override_idx(insn);
+ if (idx < 0)
+ return idx;
+
+ if (idx == INAT_SEG_REG_DEFAULT)
+ return resolve_default_seg(insn, regs, regoff);
+
+ /*
+ * In long mode, segment override prefixes are ignored, except for
+ * overrides for FS and GS.
+ */
+ if (any_64bit_mode(regs)) {
+ if (idx != INAT_SEG_REG_FS &&
+ idx != INAT_SEG_REG_GS)
+ idx = INAT_SEG_REG_IGNORE;
+ }
+
+ return idx;
+}
+
+/**
+ * get_segment_selector() - obtain segment selector
+ * @regs: Register values as seen when entering kernel mode
+ * @seg_reg_idx: Segment register index to use
+ *
+ * Obtain the segment selector from any of the CS, SS, DS, ES, FS, GS segment
+ * registers. In CONFIG_X86_32, the segment is obtained from either pt_regs or
+ * kernel_vm86_regs as applicable. In CONFIG_X86_64, CS and SS are obtained
+ * from pt_regs. DS, ES, FS and GS are obtained by reading the actual CPU
+ * registers. This done for only for completeness as in CONFIG_X86_64 segment
+ * registers are ignored.
+ *
+ * Returns:
+ *
+ * Value of the segment selector, including null when running in
+ * long mode.
+ *
+ * -EINVAL on error.
+ */
+static short get_segment_selector(struct pt_regs *regs, int seg_reg_idx)
+{
+ unsigned short sel;
+
+#ifdef CONFIG_X86_64
+ switch (seg_reg_idx) {
+ case INAT_SEG_REG_IGNORE:
+ return 0;
+ case INAT_SEG_REG_CS:
+ return (unsigned short)(regs->cs & 0xffff);
+ case INAT_SEG_REG_SS:
+ return (unsigned short)(regs->ss & 0xffff);
+ case INAT_SEG_REG_DS:
+ savesegment(ds, sel);
+ return sel;
+ case INAT_SEG_REG_ES:
+ savesegment(es, sel);
+ return sel;
+ case INAT_SEG_REG_FS:
+ savesegment(fs, sel);
+ return sel;
+ case INAT_SEG_REG_GS:
+ savesegment(gs, sel);
+ return sel;
+ default:
+ return -EINVAL;
+ }
+#else /* CONFIG_X86_32 */
+ struct kernel_vm86_regs *vm86regs = (struct kernel_vm86_regs *)regs;
+
+ if (v8086_mode(regs)) {
+ switch (seg_reg_idx) {
+ case INAT_SEG_REG_CS:
+ return (unsigned short)(regs->cs & 0xffff);
+ case INAT_SEG_REG_SS:
+ return (unsigned short)(regs->ss & 0xffff);
+ case INAT_SEG_REG_DS:
+ return vm86regs->ds;
+ case INAT_SEG_REG_ES:
+ return vm86regs->es;
+ case INAT_SEG_REG_FS:
+ return vm86regs->fs;
+ case INAT_SEG_REG_GS:
+ return vm86regs->gs;
+ case INAT_SEG_REG_IGNORE:
+ default:
+ return -EINVAL;
+ }
+ }
+
+ switch (seg_reg_idx) {
+ case INAT_SEG_REG_CS:
+ return (unsigned short)(regs->cs & 0xffff);
+ case INAT_SEG_REG_SS:
+ return (unsigned short)(regs->ss & 0xffff);
+ case INAT_SEG_REG_DS:
+ return (unsigned short)(regs->ds & 0xffff);
+ case INAT_SEG_REG_ES:
+ return (unsigned short)(regs->es & 0xffff);
+ case INAT_SEG_REG_FS:
+ return (unsigned short)(regs->fs & 0xffff);
+ case INAT_SEG_REG_GS:
+ savesegment(gs, sel);
+ return sel;
+ case INAT_SEG_REG_IGNORE:
+ default:
+ return -EINVAL;
+ }
+#endif /* CONFIG_X86_64 */
+}
+
+static const int pt_regoff[] = {
+ offsetof(struct pt_regs, ax),
+ offsetof(struct pt_regs, cx),
+ offsetof(struct pt_regs, dx),
+ offsetof(struct pt_regs, bx),
+ offsetof(struct pt_regs, sp),
+ offsetof(struct pt_regs, bp),
+ offsetof(struct pt_regs, si),
+ offsetof(struct pt_regs, di),
+#ifdef CONFIG_X86_64
+ offsetof(struct pt_regs, r8),
+ offsetof(struct pt_regs, r9),
+ offsetof(struct pt_regs, r10),
+ offsetof(struct pt_regs, r11),
+ offsetof(struct pt_regs, r12),
+ offsetof(struct pt_regs, r13),
+ offsetof(struct pt_regs, r14),
+ offsetof(struct pt_regs, r15),
+#else
+ offsetof(struct pt_regs, ds),
+ offsetof(struct pt_regs, es),
+ offsetof(struct pt_regs, fs),
+ offsetof(struct pt_regs, gs),
+#endif
+};
+
+int pt_regs_offset(struct pt_regs *regs, int regno)
+{
+ if ((unsigned)regno < ARRAY_SIZE(pt_regoff))
+ return pt_regoff[regno];
+ return -EDOM;
+}
+
+static int get_regno(struct insn *insn, enum reg_type type)
+{
+ int nr_registers = ARRAY_SIZE(pt_regoff);
+ int regno = 0;
+
+ /*
+ * Don't possibly decode a 32-bit instructions as
+ * reading a 64-bit-only register.
+ */
+ if (IS_ENABLED(CONFIG_X86_64) && !insn->x86_64)
+ nr_registers -= 8;
+
+ switch (type) {
+ case REG_TYPE_RM:
+ regno = X86_MODRM_RM(insn->modrm.value);
+
+ /*
+ * ModRM.mod == 0 and ModRM.rm == 5 means a 32-bit displacement
+ * follows the ModRM byte.
+ */
+ if (!X86_MODRM_MOD(insn->modrm.value) && regno == 5)
+ return -EDOM;
+
+ if (X86_REX_B(insn->rex_prefix.value))
+ regno += 8;
+ break;
+
+ case REG_TYPE_REG:
+ regno = X86_MODRM_REG(insn->modrm.value);
+
+ if (X86_REX_R(insn->rex_prefix.value))
+ regno += 8;
+ break;
+
+ case REG_TYPE_INDEX:
+ regno = X86_SIB_INDEX(insn->sib.value);
+ if (X86_REX_X(insn->rex_prefix.value))
+ regno += 8;
+
+ /*
+ * If ModRM.mod != 3 and SIB.index = 4 the scale*index
+ * portion of the address computation is null. This is
+ * true only if REX.X is 0. In such a case, the SIB index
+ * is used in the address computation.
+ */
+ if (X86_MODRM_MOD(insn->modrm.value) != 3 && regno == 4)
+ return -EDOM;
+ break;
+
+ case REG_TYPE_BASE:
+ regno = X86_SIB_BASE(insn->sib.value);
+ /*
+ * If ModRM.mod is 0 and SIB.base == 5, the base of the
+ * register-indirect addressing is 0. In this case, a
+ * 32-bit displacement follows the SIB byte.
+ */
+ if (!X86_MODRM_MOD(insn->modrm.value) && regno == 5)
+ return -EDOM;
+
+ if (X86_REX_B(insn->rex_prefix.value))
+ regno += 8;
+ break;
+
+ default:
+ pr_err_ratelimited("invalid register type: %d\n", type);
+ return -EINVAL;
+ }
+
+ if (regno >= nr_registers) {
+ WARN_ONCE(1, "decoded an instruction with an invalid register");
+ return -EINVAL;
+ }
+ return regno;
+}
+
+static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
+ enum reg_type type)
+{
+ int regno = get_regno(insn, type);
+
+ if (regno < 0)
+ return regno;
+
+ return pt_regs_offset(regs, regno);
+}
+
+/**
+ * get_reg_offset_16() - Obtain offset of register indicated by instruction
+ * @insn: Instruction containing ModRM byte
+ * @regs: Register values as seen when entering kernel mode
+ * @offs1: Offset of the first operand register
+ * @offs2: Offset of the second operand register, if applicable
+ *
+ * Obtain the offset, in pt_regs, of the registers indicated by the ModRM byte
+ * in @insn. This function is to be used with 16-bit address encodings. The
+ * @offs1 and @offs2 will be written with the offset of the two registers
+ * indicated by the instruction. In cases where any of the registers is not
+ * referenced by the instruction, the value will be set to -EDOM.
+ *
+ * Returns:
+ *
+ * 0 on success, -EINVAL on error.
+ */
+static int get_reg_offset_16(struct insn *insn, struct pt_regs *regs,
+ int *offs1, int *offs2)
+{
+ /*
+ * 16-bit addressing can use one or two registers. Specifics of
+ * encodings are given in Table 2-1. "16-Bit Addressing Forms with the
+ * ModR/M Byte" of the Intel Software Development Manual.
+ */
+ static const int regoff1[] = {
+ offsetof(struct pt_regs, bx),
+ offsetof(struct pt_regs, bx),
+ offsetof(struct pt_regs, bp),
+ offsetof(struct pt_regs, bp),
+ offsetof(struct pt_regs, si),
+ offsetof(struct pt_regs, di),
+ offsetof(struct pt_regs, bp),
+ offsetof(struct pt_regs, bx),
+ };
+
+ static const int regoff2[] = {
+ offsetof(struct pt_regs, si),
+ offsetof(struct pt_regs, di),
+ offsetof(struct pt_regs, si),
+ offsetof(struct pt_regs, di),
+ -EDOM,
+ -EDOM,
+ -EDOM,
+ -EDOM,
+ };
+
+ if (!offs1 || !offs2)
+ return -EINVAL;
+
+ /* Operand is a register, use the generic function. */
+ if (X86_MODRM_MOD(insn->modrm.value) == 3) {
+ *offs1 = insn_get_modrm_rm_off(insn, regs);
+ *offs2 = -EDOM;
+ return 0;
+ }
+
+ *offs1 = regoff1[X86_MODRM_RM(insn->modrm.value)];
+ *offs2 = regoff2[X86_MODRM_RM(insn->modrm.value)];
+
+ /*
+ * If ModRM.mod is 0 and ModRM.rm is 110b, then we use displacement-
+ * only addressing. This means that no registers are involved in
+ * computing the effective address. Thus, ensure that the first
+ * register offset is invalid. The second register offset is already
+ * invalid under the aforementioned conditions.
+ */
+ if ((X86_MODRM_MOD(insn->modrm.value) == 0) &&
+ (X86_MODRM_RM(insn->modrm.value) == 6))
+ *offs1 = -EDOM;
+
+ return 0;
+}
+
+/**
+ * get_desc() - Obtain contents of a segment descriptor
+ * @out: Segment descriptor contents on success
+ * @sel: Segment selector
+ *
+ * Given a segment selector, obtain a pointer to the segment descriptor.
+ * Both global and local descriptor tables are supported.
+ *
+ * Returns:
+ *
+ * True on success, false on failure.
+ *
+ * NULL on error.
+ */
+static bool get_desc(struct desc_struct *out, unsigned short sel)
+{
+ struct desc_ptr gdt_desc = {0, 0};
+ unsigned long desc_base;
+
+#ifdef CONFIG_MODIFY_LDT_SYSCALL
+ if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT) {
+ bool success = false;
+ struct ldt_struct *ldt;
+
+ /* Bits [15:3] contain the index of the desired entry. */
+ sel >>= 3;
+
+ mutex_lock(¤t->active_mm->context.lock);
+ ldt = current->active_mm->context.ldt;
+ if (ldt && sel < ldt->nr_entries) {
+ *out = ldt->entries[sel];
+ success = true;
+ }
+
+ mutex_unlock(¤t->active_mm->context.lock);
+
+ return success;
+ }
+#endif
+ native_store_gdt(&gdt_desc);
+
+ /*
+ * Segment descriptors have a size of 8 bytes. Thus, the index is
+ * multiplied by 8 to obtain the memory offset of the desired descriptor
+ * from the base of the GDT. As bits [15:3] of the segment selector
+ * contain the index, it can be regarded as multiplied by 8 already.
+ * All that remains is to clear bits [2:0].
+ */
+ desc_base = sel & ~(SEGMENT_RPL_MASK | SEGMENT_TI_MASK);
+
+ if (desc_base > gdt_desc.size)
+ return false;
+
+ *out = *(struct desc_struct *)(gdt_desc.address + desc_base);
+ return true;
+}
+
+/**
+ * insn_get_seg_base() - Obtain base address of segment descriptor.
+ * @regs: Register values as seen when entering kernel mode
+ * @seg_reg_idx: Index of the segment register pointing to seg descriptor
+ *
+ * Obtain the base address of the segment as indicated by the segment descriptor
+ * pointed by the segment selector. The segment selector is obtained from the
+ * input segment register index @seg_reg_idx.
+ *
+ * Returns:
+ *
+ * In protected mode, base address of the segment. Zero in long mode,
+ * except when FS or GS are used. In virtual-8086 mode, the segment
+ * selector shifted 4 bits to the right.
+ *
+ * -1L in case of error.
+ */
+unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx)
+{
+ struct desc_struct desc;
+ short sel;
+
+ sel = get_segment_selector(regs, seg_reg_idx);
+ if (sel < 0)
+ return -1L;
+
+ if (v8086_mode(regs))
+ /*
+ * Base is simply the segment selector shifted 4
+ * bits to the right.
+ */
+ return (unsigned long)(sel << 4);
+
+ if (any_64bit_mode(regs)) {
+ /*
+ * Only FS or GS will have a base address, the rest of
+ * the segments' bases are forced to 0.
+ */
+ unsigned long base;
+
+ if (seg_reg_idx == INAT_SEG_REG_FS) {
+ rdmsrl(MSR_FS_BASE, base);
+ } else if (seg_reg_idx == INAT_SEG_REG_GS) {
+ /*
+ * swapgs was called at the kernel entry point. Thus,
+ * MSR_KERNEL_GS_BASE will have the user-space GS base.
+ */
+ if (user_mode(regs))
+ rdmsrl(MSR_KERNEL_GS_BASE, base);
+ else
+ rdmsrl(MSR_GS_BASE, base);
+ } else {
+ base = 0;
+ }
+ return base;
+ }
+
+ /* In protected mode the segment selector cannot be null. */
+ if (!sel)
+ return -1L;
+
+ if (!get_desc(&desc, sel))
+ return -1L;
+
+ return get_desc_base(&desc);
+}
+
+/**
+ * get_seg_limit() - Obtain the limit of a segment descriptor
+ * @regs: Register values as seen when entering kernel mode
+ * @seg_reg_idx: Index of the segment register pointing to seg descriptor
+ *
+ * Obtain the limit of the segment as indicated by the segment descriptor
+ * pointed by the segment selector. The segment selector is obtained from the
+ * input segment register index @seg_reg_idx.
+ *
+ * Returns:
+ *
+ * In protected mode, the limit of the segment descriptor in bytes.
+ * In long mode and virtual-8086 mode, segment limits are not enforced. Thus,
+ * limit is returned as -1L to imply a limit-less segment.
+ *
+ * Zero is returned on error.
+ */
+static unsigned long get_seg_limit(struct pt_regs *regs, int seg_reg_idx)
+{
+ struct desc_struct desc;
+ unsigned long limit;
+ short sel;
+
+ sel = get_segment_selector(regs, seg_reg_idx);
+ if (sel < 0)
+ return 0;
+
+ if (any_64bit_mode(regs) || v8086_mode(regs))
+ return -1L;
+
+ if (!sel)
+ return 0;
+
+ if (!get_desc(&desc, sel))
+ return 0;
+
+ /*
+ * If the granularity bit is set, the limit is given in multiples
+ * of 4096. This also means that the 12 least significant bits are
+ * not tested when checking the segment limits. In practice,
+ * this means that the segment ends in (limit << 12) + 0xfff.
+ */
+ limit = get_desc_limit(&desc);
+ if (desc.g)
+ limit = (limit << 12) + 0xfff;
+
+ return limit;
+}
+
+/**
+ * insn_get_code_seg_params() - Obtain code segment parameters
+ * @regs: Structure with register values as seen when entering kernel mode
+ *
+ * Obtain address and operand sizes of the code segment. It is obtained from the
+ * selector contained in the CS register in regs. In protected mode, the default
+ * address is determined by inspecting the L and D bits of the segment
+ * descriptor. In virtual-8086 mode, the default is always two bytes for both
+ * address and operand sizes.
+ *
+ * Returns:
+ *
+ * An int containing ORed-in default parameters on success.
+ *
+ * -EINVAL on error.
+ */
+int insn_get_code_seg_params(struct pt_regs *regs)
+{
+ struct desc_struct desc;
+ short sel;
+
+ if (v8086_mode(regs))
+ /* Address and operand size are both 16-bit. */
+ return INSN_CODE_SEG_PARAMS(2, 2);
+
+ sel = get_segment_selector(regs, INAT_SEG_REG_CS);
+ if (sel < 0)
+ return sel;
+
+ if (!get_desc(&desc, sel))
+ return -EINVAL;
+
+ /*
+ * The most significant byte of the Type field of the segment descriptor
+ * determines whether a segment contains data or code. If this is a data
+ * segment, return error.
+ */
+ if (!(desc.type & BIT(3)))
+ return -EINVAL;
+
+ switch ((desc.l << 1) | desc.d) {
+ case 0: /*
+ * Legacy mode. CS.L=0, CS.D=0. Address and operand size are
+ * both 16-bit.
+ */
+ return INSN_CODE_SEG_PARAMS(2, 2);
+ case 1: /*
+ * Legacy mode. CS.L=0, CS.D=1. Address and operand size are
+ * both 32-bit.
+ */
+ return INSN_CODE_SEG_PARAMS(4, 4);
+ case 2: /*
+ * IA-32e 64-bit mode. CS.L=1, CS.D=0. Address size is 64-bit;
+ * operand size is 32-bit.
+ */
+ return INSN_CODE_SEG_PARAMS(4, 8);
+ case 3: /* Invalid setting. CS.L=1, CS.D=1 */
+ fallthrough;
+ default:
+ return -EINVAL;
+ }
+}
+
+/**
+ * insn_get_modrm_rm_off() - Obtain register in r/m part of the ModRM byte
+ * @insn: Instruction containing the ModRM byte
+ * @regs: Register values as seen when entering kernel mode
+ *
+ * Returns:
+ *
+ * The register indicated by the r/m part of the ModRM byte. The
+ * register is obtained as an offset from the base of pt_regs. In specific
+ * cases, the returned value can be -EDOM to indicate that the particular value
+ * of ModRM does not refer to a register and shall be ignored.
+ */
+int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs)
+{
+ return get_reg_offset(insn, regs, REG_TYPE_RM);
+}
+
+/**
+ * insn_get_modrm_reg_off() - Obtain register in reg part of the ModRM byte
+ * @insn: Instruction containing the ModRM byte
+ * @regs: Register values as seen when entering kernel mode
+ *
+ * Returns:
+ *
+ * The register indicated by the reg part of the ModRM byte. The
+ * register is obtained as an offset from the base of pt_regs.
+ */
+int insn_get_modrm_reg_off(struct insn *insn, struct pt_regs *regs)
+{
+ return get_reg_offset(insn, regs, REG_TYPE_REG);
+}
+
+/**
+ * insn_get_modrm_reg_ptr() - Obtain register pointer based on ModRM byte
+ * @insn: Instruction containing the ModRM byte
+ * @regs: Register values as seen when entering kernel mode
+ *
+ * Returns:
+ *
+ * The register indicated by the reg part of the ModRM byte.
+ * The register is obtained as a pointer within pt_regs.
+ */
+unsigned long *insn_get_modrm_reg_ptr(struct insn *insn, struct pt_regs *regs)
+{
+ int offset;
+
+ offset = insn_get_modrm_reg_off(insn, regs);
+ if (offset < 0)
+ return NULL;
+ return (void *)regs + offset;
+}
+
+/**
+ * get_seg_base_limit() - obtain base address and limit of a segment
+ * @insn: Instruction. Must be valid.
+ * @regs: Register values as seen when entering kernel mode
+ * @regoff: Operand offset, in pt_regs, used to resolve segment descriptor
+ * @base: Obtained segment base
+ * @limit: Obtained segment limit
+ *
+ * Obtain the base address and limit of the segment associated with the operand
+ * @regoff and, if any or allowed, override prefixes in @insn. This function is
+ * different from insn_get_seg_base() as the latter does not resolve the segment
+ * associated with the instruction operand. If a limit is not needed (e.g.,
+ * when running in long mode), @limit can be NULL.
+ *
+ * Returns:
+ *
+ * 0 on success. @base and @limit will contain the base address and of the
+ * resolved segment, respectively.
+ *
+ * -EINVAL on error.
+ */
+static int get_seg_base_limit(struct insn *insn, struct pt_regs *regs,
+ int regoff, unsigned long *base,
+ unsigned long *limit)
+{
+ int seg_reg_idx;
+
+ if (!base)
+ return -EINVAL;
+
+ seg_reg_idx = resolve_seg_reg(insn, regs, regoff);
+ if (seg_reg_idx < 0)
+ return seg_reg_idx;
+
+ *base = insn_get_seg_base(regs, seg_reg_idx);
+ if (*base == -1L)
+ return -EINVAL;
+
+ if (!limit)
+ return 0;
+
+ *limit = get_seg_limit(regs, seg_reg_idx);
+ if (!(*limit))
+ return -EINVAL;
+
+ return 0;
+}
+
+/**
+ * get_eff_addr_reg() - Obtain effective address from register operand
+ * @insn: Instruction. Must be valid.
+ * @regs: Register values as seen when entering kernel mode
+ * @regoff: Obtained operand offset, in pt_regs, with the effective address
+ * @eff_addr: Obtained effective address
+ *
+ * Obtain the effective address stored in the register operand as indicated by
+ * the ModRM byte. This function is to be used only with register addressing
+ * (i.e., ModRM.mod is 3). The effective address is saved in @eff_addr. The
+ * register operand, as an offset from the base of pt_regs, is saved in @regoff;
+ * such offset can then be used to resolve the segment associated with the
+ * operand. This function can be used with any of the supported address sizes
+ * in x86.
+ *
+ * Returns:
+ *
+ * 0 on success. @eff_addr will have the effective address stored in the
+ * operand indicated by ModRM. @regoff will have such operand as an offset from
+ * the base of pt_regs.
+ *
+ * -EINVAL on error.
+ */
+static int get_eff_addr_reg(struct insn *insn, struct pt_regs *regs,
+ int *regoff, long *eff_addr)
+{
+ int ret;
+
+ ret = insn_get_modrm(insn);
+ if (ret)
+ return ret;
+
+ if (X86_MODRM_MOD(insn->modrm.value) != 3)
+ return -EINVAL;
+
+ *regoff = get_reg_offset(insn, regs, REG_TYPE_RM);
+ if (*regoff < 0)
+ return -EINVAL;
+
+ /* Ignore bytes that are outside the address size. */
+ if (insn->addr_bytes == 2)
+ *eff_addr = regs_get_register(regs, *regoff) & 0xffff;
+ else if (insn->addr_bytes == 4)
+ *eff_addr = regs_get_register(regs, *regoff) & 0xffffffff;
+ else /* 64-bit address */
+ *eff_addr = regs_get_register(regs, *regoff);
+
+ return 0;
+}
+
+/**
+ * get_eff_addr_modrm() - Obtain referenced effective address via ModRM
+ * @insn: Instruction. Must be valid.
+ * @regs: Register values as seen when entering kernel mode
+ * @regoff: Obtained operand offset, in pt_regs, associated with segment
+ * @eff_addr: Obtained effective address
+ *
+ * Obtain the effective address referenced by the ModRM byte of @insn. After
+ * identifying the registers involved in the register-indirect memory reference,
+ * its value is obtained from the operands in @regs. The computed address is
+ * stored @eff_addr. Also, the register operand that indicates the associated
+ * segment is stored in @regoff, this parameter can later be used to determine
+ * such segment.
+ *
+ * Returns:
+ *
+ * 0 on success. @eff_addr will have the referenced effective address. @regoff
+ * will have a register, as an offset from the base of pt_regs, that can be used
+ * to resolve the associated segment.
+ *
+ * -EINVAL on error.
+ */
+static int get_eff_addr_modrm(struct insn *insn, struct pt_regs *regs,
+ int *regoff, long *eff_addr)
+{
+ long tmp;
+ int ret;
+
+ if (insn->addr_bytes != 8 && insn->addr_bytes != 4)
+ return -EINVAL;
+
+ ret = insn_get_modrm(insn);
+ if (ret)
+ return ret;
+
+ if (X86_MODRM_MOD(insn->modrm.value) > 2)
+ return -EINVAL;
+
+ *regoff = get_reg_offset(insn, regs, REG_TYPE_RM);
+
+ /*
+ * -EDOM means that we must ignore the address_offset. In such a case,
+ * in 64-bit mode the effective address relative to the rIP of the
+ * following instruction.
+ */
+ if (*regoff == -EDOM) {
+ if (any_64bit_mode(regs))
+ tmp = regs->ip + insn->length;
+ else
+ tmp = 0;
+ } else if (*regoff < 0) {
+ return -EINVAL;
+ } else {
+ tmp = regs_get_register(regs, *regoff);
+ }
+
+ if (insn->addr_bytes == 4) {
+ int addr32 = (int)(tmp & 0xffffffff) + insn->displacement.value;
+
+ *eff_addr = addr32 & 0xffffffff;
+ } else {
+ *eff_addr = tmp + insn->displacement.value;
+ }
+
+ return 0;
+}
+
+/**
+ * get_eff_addr_modrm_16() - Obtain referenced effective address via ModRM
+ * @insn: Instruction. Must be valid.
+ * @regs: Register values as seen when entering kernel mode
+ * @regoff: Obtained operand offset, in pt_regs, associated with segment
+ * @eff_addr: Obtained effective address
+ *
+ * Obtain the 16-bit effective address referenced by the ModRM byte of @insn.
+ * After identifying the registers involved in the register-indirect memory
+ * reference, its value is obtained from the operands in @regs. The computed
+ * address is stored @eff_addr. Also, the register operand that indicates
+ * the associated segment is stored in @regoff, this parameter can later be used
+ * to determine such segment.
+ *
+ * Returns:
+ *
+ * 0 on success. @eff_addr will have the referenced effective address. @regoff
+ * will have a register, as an offset from the base of pt_regs, that can be used
+ * to resolve the associated segment.
+ *
+ * -EINVAL on error.
+ */
+static int get_eff_addr_modrm_16(struct insn *insn, struct pt_regs *regs,
+ int *regoff, short *eff_addr)
+{
+ int addr_offset1, addr_offset2, ret;
+ short addr1 = 0, addr2 = 0, displacement;
+
+ if (insn->addr_bytes != 2)
+ return -EINVAL;
+
+ insn_get_modrm(insn);
+
+ if (!insn->modrm.nbytes)
+ return -EINVAL;
+
+ if (X86_MODRM_MOD(insn->modrm.value) > 2)
+ return -EINVAL;
+
+ ret = get_reg_offset_16(insn, regs, &addr_offset1, &addr_offset2);
+ if (ret < 0)
+ return -EINVAL;
+
+ /*
+ * Don't fail on invalid offset values. They might be invalid because
+ * they cannot be used for this particular value of ModRM. Instead, use
+ * them in the computation only if they contain a valid value.
+ */
+ if (addr_offset1 != -EDOM)
+ addr1 = regs_get_register(regs, addr_offset1) & 0xffff;
+
+ if (addr_offset2 != -EDOM)
+ addr2 = regs_get_register(regs, addr_offset2) & 0xffff;
+
+ displacement = insn->displacement.value & 0xffff;
+ *eff_addr = addr1 + addr2 + displacement;
+
+ /*
+ * The first operand register could indicate to use of either SS or DS
+ * registers to obtain the segment selector. The second operand
+ * register can only indicate the use of DS. Thus, the first operand
+ * will be used to obtain the segment selector.
+ */
+ *regoff = addr_offset1;
+
+ return 0;
+}
+
+/**
+ * get_eff_addr_sib() - Obtain referenced effective address via SIB
+ * @insn: Instruction. Must be valid.
+ * @regs: Register values as seen when entering kernel mode
+ * @base_offset: Obtained operand offset, in pt_regs, associated with segment
+ * @eff_addr: Obtained effective address
+ *
+ * Obtain the effective address referenced by the SIB byte of @insn. After
+ * identifying the registers involved in the indexed, register-indirect memory
+ * reference, its value is obtained from the operands in @regs. The computed
+ * address is stored @eff_addr. Also, the register operand that indicates the
+ * associated segment is stored in @base_offset; this parameter can later be
+ * used to determine such segment.
+ *
+ * Returns:
+ *
+ * 0 on success. @eff_addr will have the referenced effective address.
+ * @base_offset will have a register, as an offset from the base of pt_regs,
+ * that can be used to resolve the associated segment.
+ *
+ * Negative value on error.
+ */
+static int get_eff_addr_sib(struct insn *insn, struct pt_regs *regs,
+ int *base_offset, long *eff_addr)
+{
+ long base, indx;
+ int indx_offset;
+ int ret;
+
+ if (insn->addr_bytes != 8 && insn->addr_bytes != 4)
+ return -EINVAL;
+
+ ret = insn_get_modrm(insn);
+ if (ret)
+ return ret;
+
+ if (!insn->modrm.nbytes)
+ return -EINVAL;
+
+ if (X86_MODRM_MOD(insn->modrm.value) > 2)
+ return -EINVAL;
+
+ ret = insn_get_sib(insn);
+ if (ret)
+ return ret;
+
+ if (!insn->sib.nbytes)
+ return -EINVAL;
+
+ *base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE);
+ indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX);
+
+ /*
+ * Negative values in the base and index offset means an error when
+ * decoding the SIB byte. Except -EDOM, which means that the registers
+ * should not be used in the address computation.
+ */
+ if (*base_offset == -EDOM)
+ base = 0;
+ else if (*base_offset < 0)
+ return -EINVAL;
+ else
+ base = regs_get_register(regs, *base_offset);
+
+ if (indx_offset == -EDOM)
+ indx = 0;
+ else if (indx_offset < 0)
+ return -EINVAL;
+ else
+ indx = regs_get_register(regs, indx_offset);
+
+ if (insn->addr_bytes == 4) {
+ int addr32, base32, idx32;
+
+ base32 = base & 0xffffffff;
+ idx32 = indx & 0xffffffff;
+
+ addr32 = base32 + idx32 * (1 << X86_SIB_SCALE(insn->sib.value));
+ addr32 += insn->displacement.value;
+
+ *eff_addr = addr32 & 0xffffffff;
+ } else {
+ *eff_addr = base + indx * (1 << X86_SIB_SCALE(insn->sib.value));
+ *eff_addr += insn->displacement.value;
+ }
+
+ return 0;
+}
+
+/**
+ * get_addr_ref_16() - Obtain the 16-bit address referred by instruction
+ * @insn: Instruction containing ModRM byte and displacement
+ * @regs: Register values as seen when entering kernel mode
+ *
+ * This function is to be used with 16-bit address encodings. Obtain the memory
+ * address referred by the instruction's ModRM and displacement bytes. Also, the
+ * segment used as base is determined by either any segment override prefixes in
+ * @insn or the default segment of the registers involved in the address
+ * computation. In protected mode, segment limits are enforced.
+ *
+ * Returns:
+ *
+ * Linear address referenced by the instruction operands on success.
+ *
+ * -1L on error.
+ */
+static void __user *get_addr_ref_16(struct insn *insn, struct pt_regs *regs)
+{
+ unsigned long linear_addr = -1L, seg_base, seg_limit;
+ int ret, regoff;
+ short eff_addr;
+ long tmp;
+
+ if (insn_get_displacement(insn))
+ goto out;
+
+ if (insn->addr_bytes != 2)
+ goto out;
+
+ if (X86_MODRM_MOD(insn->modrm.value) == 3) {
+ ret = get_eff_addr_reg(insn, regs, ®off, &tmp);
+ if (ret)
+ goto out;
+
+ eff_addr = tmp;
+ } else {
+ ret = get_eff_addr_modrm_16(insn, regs, ®off, &eff_addr);
+ if (ret)
+ goto out;
+ }
+
+ ret = get_seg_base_limit(insn, regs, regoff, &seg_base, &seg_limit);
+ if (ret)
+ goto out;
+
+ /*
+ * Before computing the linear address, make sure the effective address
+ * is within the limits of the segment. In virtual-8086 mode, segment
+ * limits are not enforced. In such a case, the segment limit is -1L to
+ * reflect this fact.
+ */
+ if ((unsigned long)(eff_addr & 0xffff) > seg_limit)
+ goto out;
+
+ linear_addr = (unsigned long)(eff_addr & 0xffff) + seg_base;
+
+ /* Limit linear address to 20 bits */
+ if (v8086_mode(regs))
+ linear_addr &= 0xfffff;
+
+out:
+ return (void __user *)linear_addr;
+}
+
+/**
+ * get_addr_ref_32() - Obtain a 32-bit linear address
+ * @insn: Instruction with ModRM, SIB bytes and displacement
+ * @regs: Register values as seen when entering kernel mode
+ *
+ * This function is to be used with 32-bit address encodings to obtain the
+ * linear memory address referred by the instruction's ModRM, SIB,
+ * displacement bytes and segment base address, as applicable. If in protected
+ * mode, segment limits are enforced.
+ *
+ * Returns:
+ *
+ * Linear address referenced by instruction and registers on success.
+ *
+ * -1L on error.
+ */
+static void __user *get_addr_ref_32(struct insn *insn, struct pt_regs *regs)
+{
+ unsigned long linear_addr = -1L, seg_base, seg_limit;
+ int eff_addr, regoff;
+ long tmp;
+ int ret;
+
+ if (insn->addr_bytes != 4)
+ goto out;
+
+ if (X86_MODRM_MOD(insn->modrm.value) == 3) {
+ ret = get_eff_addr_reg(insn, regs, ®off, &tmp);
+ if (ret)
+ goto out;
+
+ eff_addr = tmp;
+
+ } else {
+ if (insn->sib.nbytes) {
+ ret = get_eff_addr_sib(insn, regs, ®off, &tmp);
+ if (ret)
+ goto out;
+
+ eff_addr = tmp;
+ } else {
+ ret = get_eff_addr_modrm(insn, regs, ®off, &tmp);
+ if (ret)
+ goto out;
+
+ eff_addr = tmp;
+ }
+ }
+
+ ret = get_seg_base_limit(insn, regs, regoff, &seg_base, &seg_limit);
+ if (ret)
+ goto out;
+
+ /*
+ * In protected mode, before computing the linear address, make sure
+ * the effective address is within the limits of the segment.
+ * 32-bit addresses can be used in long and virtual-8086 modes if an
+ * address override prefix is used. In such cases, segment limits are
+ * not enforced. When in virtual-8086 mode, the segment limit is -1L
+ * to reflect this situation.
+ *
+ * After computed, the effective address is treated as an unsigned
+ * quantity.
+ */
+ if (!any_64bit_mode(regs) && ((unsigned int)eff_addr > seg_limit))
+ goto out;
+
+ /*
+ * Even though 32-bit address encodings are allowed in virtual-8086
+ * mode, the address range is still limited to [0x-0xffff].
+ */
+ if (v8086_mode(regs) && (eff_addr & ~0xffff))
+ goto out;
+
+ /*
+ * Data type long could be 64 bits in size. Ensure that our 32-bit
+ * effective address is not sign-extended when computing the linear
+ * address.
+ */
+ linear_addr = (unsigned long)(eff_addr & 0xffffffff) + seg_base;
+
+ /* Limit linear address to 20 bits */
+ if (v8086_mode(regs))
+ linear_addr &= 0xfffff;
+
+out:
+ return (void __user *)linear_addr;
+}
+
+/**
+ * get_addr_ref_64() - Obtain a 64-bit linear address
+ * @insn: Instruction struct with ModRM and SIB bytes and displacement
+ * @regs: Structure with register values as seen when entering kernel mode
+ *
+ * This function is to be used with 64-bit address encodings to obtain the
+ * linear memory address referred by the instruction's ModRM, SIB,
+ * displacement bytes and segment base address, as applicable.
+ *
+ * Returns:
+ *
+ * Linear address referenced by instruction and registers on success.
+ *
+ * -1L on error.
+ */
+#ifndef CONFIG_X86_64
+static void __user *get_addr_ref_64(struct insn *insn, struct pt_regs *regs)
+{
+ return (void __user *)-1L;
+}
+#else
+static void __user *get_addr_ref_64(struct insn *insn, struct pt_regs *regs)
+{
+ unsigned long linear_addr = -1L, seg_base;
+ int regoff, ret;
+ long eff_addr;
+
+ if (insn->addr_bytes != 8)
+ goto out;
+
+ if (X86_MODRM_MOD(insn->modrm.value) == 3) {
+ ret = get_eff_addr_reg(insn, regs, ®off, &eff_addr);
+ if (ret)
+ goto out;
+
+ } else {
+ if (insn->sib.nbytes) {
+ ret = get_eff_addr_sib(insn, regs, ®off, &eff_addr);
+ if (ret)
+ goto out;
+ } else {
+ ret = get_eff_addr_modrm(insn, regs, ®off, &eff_addr);
+ if (ret)
+ goto out;
+ }
+
+ }
+
+ ret = get_seg_base_limit(insn, regs, regoff, &seg_base, NULL);
+ if (ret)
+ goto out;
+
+ linear_addr = (unsigned long)eff_addr + seg_base;
+
+out:
+ return (void __user *)linear_addr;
+}
+#endif /* CONFIG_X86_64 */
+
+/**
+ * insn_get_addr_ref() - Obtain the linear address referred by instruction
+ * @insn: Instruction structure containing ModRM byte and displacement
+ * @regs: Structure with register values as seen when entering kernel mode
+ *
+ * Obtain the linear address referred by the instruction's ModRM, SIB and
+ * displacement bytes, and segment base, as applicable. In protected mode,
+ * segment limits are enforced.
+ *
+ * Returns:
+ *
+ * Linear address referenced by instruction and registers on success.
+ *
+ * -1L on error.
+ */
+void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
+{
+ if (!insn || !regs)
+ return (void __user *)-1L;
+
+ if (insn_get_opcode(insn))
+ return (void __user *)-1L;
+
+ switch (insn->addr_bytes) {
+ case 2:
+ return get_addr_ref_16(insn, regs);
+ case 4:
+ return get_addr_ref_32(insn, regs);
+ case 8:
+ return get_addr_ref_64(insn, regs);
+ default:
+ return (void __user *)-1L;
+ }
+}
+
+int insn_get_effective_ip(struct pt_regs *regs, unsigned long *ip)
+{
+ unsigned long seg_base = 0;
+
+ /*
+ * If not in user-space long mode, a custom code segment could be in
+ * use. This is true in protected mode (if the process defined a local
+ * descriptor table), or virtual-8086 mode. In most of the cases
+ * seg_base will be zero as in USER_CS.
+ */
+ if (!user_64bit_mode(regs)) {
+ seg_base = insn_get_seg_base(regs, INAT_SEG_REG_CS);
+ if (seg_base == -1L)
+ return -EINVAL;
+ }
+
+ *ip = seg_base + regs->ip;
+
+ return 0;
+}
+
+/**
+ * insn_fetch_from_user() - Copy instruction bytes from user-space memory
+ * @regs: Structure with register values as seen when entering kernel mode
+ * @buf: Array to store the fetched instruction
+ *
+ * Gets the linear address of the instruction and copies the instruction bytes
+ * to the buf.
+ *
+ * Returns:
+ *
+ * - number of instruction bytes copied.
+ * - 0 if nothing was copied.
+ * - -EINVAL if the linear address of the instruction could not be calculated
+ */
+int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE])
+{
+ unsigned long ip;
+ int not_copied;
+
+ if (insn_get_effective_ip(regs, &ip))
+ return -EINVAL;
+
+ not_copied = copy_from_user(buf, (void __user *)ip, MAX_INSN_SIZE);
+
+ return MAX_INSN_SIZE - not_copied;
+}
+
+/**
+ * insn_fetch_from_user_inatomic() - Copy instruction bytes from user-space memory
+ * while in atomic code
+ * @regs: Structure with register values as seen when entering kernel mode
+ * @buf: Array to store the fetched instruction
+ *
+ * Gets the linear address of the instruction and copies the instruction bytes
+ * to the buf. This function must be used in atomic context.
+ *
+ * Returns:
+ *
+ * - number of instruction bytes copied.
+ * - 0 if nothing was copied.
+ * - -EINVAL if the linear address of the instruction could not be calculated.
+ */
+int insn_fetch_from_user_inatomic(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE])
+{
+ unsigned long ip;
+ int not_copied;
+
+ if (insn_get_effective_ip(regs, &ip))
+ return -EINVAL;
+
+ not_copied = __copy_from_user_inatomic(buf, (void __user *)ip, MAX_INSN_SIZE);
+
+ return MAX_INSN_SIZE - not_copied;
+}
+
+/**
+ * insn_decode_from_regs() - Decode an instruction
+ * @insn: Structure to store decoded instruction
+ * @regs: Structure with register values as seen when entering kernel mode
+ * @buf: Buffer containing the instruction bytes
+ * @buf_size: Number of instruction bytes available in buf
+ *
+ * Decodes the instruction provided in buf and stores the decoding results in
+ * insn. Also determines the correct address and operand sizes.
+ *
+ * Returns:
+ *
+ * True if instruction was decoded, False otherwise.
+ */
+bool insn_decode_from_regs(struct insn *insn, struct pt_regs *regs,
+ unsigned char buf[MAX_INSN_SIZE], int buf_size)
+{
+ int seg_defs;
+
+ insn_init(insn, buf, buf_size, user_64bit_mode(regs));
+
+ /*
+ * Override the default operand and address sizes with what is specified
+ * in the code segment descriptor. The instruction decoder only sets
+ * the address size it to either 4 or 8 address bytes and does nothing
+ * for the operand bytes. This OK for most of the cases, but we could
+ * have special cases where, for instance, a 16-bit code segment
+ * descriptor is used.
+ * If there is an address override prefix, the instruction decoder
+ * correctly updates these values, even for 16-bit defaults.
+ */
+ seg_defs = insn_get_code_seg_params(regs);
+ if (seg_defs == -EINVAL)
+ return false;
+
+ insn->addr_bytes = INSN_CODE_SEG_ADDR_SZ(seg_defs);
+ insn->opnd_bytes = INSN_CODE_SEG_OPND_SZ(seg_defs);
+
+ if (insn_get_length(insn))
+ return false;
+
+ if (buf_size < insn->length)
+ return false;
+
+ return true;
+}
+
+/**
+ * insn_decode_mmio() - Decode a MMIO instruction
+ * @insn: Structure to store decoded instruction
+ * @bytes: Returns size of memory operand
+ *
+ * Decodes instruction that used for Memory-mapped I/O.
+ *
+ * Returns:
+ *
+ * Type of the instruction. Size of the memory operand is stored in
+ * @bytes. If decode failed, INSN_MMIO_DECODE_FAILED returned.
+ */
+enum insn_mmio_type insn_decode_mmio(struct insn *insn, int *bytes)
+{
+ enum insn_mmio_type type = INSN_MMIO_DECODE_FAILED;
+
+ *bytes = 0;
+
+ if (insn_get_opcode(insn))
+ return INSN_MMIO_DECODE_FAILED;
+
+ switch (insn->opcode.bytes[0]) {
+ case 0x88: /* MOV m8,r8 */
+ *bytes = 1;
+ fallthrough;
+ case 0x89: /* MOV m16/m32/m64, r16/m32/m64 */
+ if (!*bytes)
+ *bytes = insn->opnd_bytes;
+ type = INSN_MMIO_WRITE;
+ break;
+
+ case 0xc6: /* MOV m8, imm8 */
+ *bytes = 1;
+ fallthrough;
+ case 0xc7: /* MOV m16/m32/m64, imm16/imm32/imm64 */
+ if (!*bytes)
+ *bytes = insn->opnd_bytes;
+ type = INSN_MMIO_WRITE_IMM;
+ break;
+
+ case 0x8a: /* MOV r8, m8 */
+ *bytes = 1;
+ fallthrough;
+ case 0x8b: /* MOV r16/r32/r64, m16/m32/m64 */
+ if (!*bytes)
+ *bytes = insn->opnd_bytes;
+ type = INSN_MMIO_READ;
+ break;
+
+ case 0xa4: /* MOVS m8, m8 */
+ *bytes = 1;
+ fallthrough;
+ case 0xa5: /* MOVS m16/m32/m64, m16/m32/m64 */
+ if (!*bytes)
+ *bytes = insn->opnd_bytes;
+ type = INSN_MMIO_MOVS;
+ break;
+
+ case 0x0f: /* Two-byte instruction */
+ switch (insn->opcode.bytes[1]) {
+ case 0xb6: /* MOVZX r16/r32/r64, m8 */
+ *bytes = 1;
+ fallthrough;
+ case 0xb7: /* MOVZX r32/r64, m16 */
+ if (!*bytes)
+ *bytes = 2;
+ type = INSN_MMIO_READ_ZERO_EXTEND;
+ break;
+
+ case 0xbe: /* MOVSX r16/r32/r64, m8 */
+ *bytes = 1;
+ fallthrough;
+ case 0xbf: /* MOVSX r32/r64, m16 */
+ if (!*bytes)
+ *bytes = 2;
+ type = INSN_MMIO_READ_SIGN_EXTEND;
+ break;
+ }
+ break;
+ }
+
+ return type;
+}
--
2.34.1
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