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Message-ID: <20211103210709.31790-1-surajjs@amazon.com>
Date: Wed, 3 Nov 2021 14:07:09 -0700
From: Suraj Jitindar Singh <surajjs@...zon.com>
To: <linux-arm-kernel@...ts.infradead.org>
CC: <linux-kernel@...r.kernel.org>, <live-patching@...r.kernel.org>,
<catalin.marinas@....com>, <will@...nel.org>,
<sjitindarsingh@...il.com>,
Suraj Jitindar Singh <surajjs@...zon.com>
Subject: [PATCH] arm64: module: Use aarch64_insn_write when updating relocations later on
Livepatch modules have relocation sections named
.klp.rela.objname.section_name which are written on module load by calling
klp_apply_section_relocs(). This is called in apply_relocations() to write
relocations targeting objects in the vmlinux, before the module text is
mapped read-only in complete_formation(). However relocations which target
other modules are not written until after the mapping is made read-only
causing them to fault.
Avoid this fault by calling aarch64_insn_write() to update the instruction
if the module text has already been marked read-only. Preserve the current
behaviour if called before this has been done.
Signed-off-by: Suraj Jitindar Singh <surajjs@...zon.com>
---
arch/arm64/kernel/module.c | 81 ++++++++++++++++++++++----------------
1 file changed, 47 insertions(+), 34 deletions(-)
diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
index b5ec010c481f..35596ea870ab 100644
--- a/arch/arm64/kernel/module.c
+++ b/arch/arm64/kernel/module.c
@@ -19,6 +19,7 @@
#include <asm/alternative.h>
#include <asm/insn.h>
#include <asm/sections.h>
+#include <asm/patching.h>
void *module_alloc(unsigned long size)
{
@@ -155,7 +156,8 @@ enum aarch64_insn_movw_imm_type {
};
static int reloc_insn_movw(enum aarch64_reloc_op op, __le32 *place, u64 val,
- int lsb, enum aarch64_insn_movw_imm_type imm_type)
+ int lsb, enum aarch64_insn_movw_imm_type imm_type,
+ bool early)
{
u64 imm;
s64 sval;
@@ -187,7 +189,10 @@ static int reloc_insn_movw(enum aarch64_reloc_op op, __le32 *place, u64 val,
/* Update the instruction with the new encoding. */
insn = aarch64_insn_encode_immediate(AARCH64_INSN_IMM_16, insn, imm);
- *place = cpu_to_le32(insn);
+ if (early)
+ *place = cpu_to_le32(insn);
+ else
+ aarch64_insn_write(place, insn);
if (imm > U16_MAX)
return -ERANGE;
@@ -196,7 +201,8 @@ static int reloc_insn_movw(enum aarch64_reloc_op op, __le32 *place, u64 val,
}
static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 *place, u64 val,
- int lsb, int len, enum aarch64_insn_imm_type imm_type)
+ int lsb, int len, enum aarch64_insn_imm_type imm_type,
+ bool early)
{
u64 imm, imm_mask;
s64 sval;
@@ -212,7 +218,10 @@ static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 *place, u64 val,
/* Update the instruction's immediate field. */
insn = aarch64_insn_encode_immediate(imm_type, insn, imm);
- *place = cpu_to_le32(insn);
+ if (early)
+ *place = cpu_to_le32(insn);
+ else
+ aarch64_insn_write(place, insn);
/*
* Extract the upper value bits (including the sign bit) and
@@ -231,17 +240,17 @@ static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 *place, u64 val,
}
static int reloc_insn_adrp(struct module *mod, Elf64_Shdr *sechdrs,
- __le32 *place, u64 val)
+ __le32 *place, u64 val, bool early)
{
u32 insn;
if (!is_forbidden_offset_for_adrp(place))
return reloc_insn_imm(RELOC_OP_PAGE, place, val, 12, 21,
- AARCH64_INSN_IMM_ADR);
+ AARCH64_INSN_IMM_ADR, early);
/* patch ADRP to ADR if it is in range */
if (!reloc_insn_imm(RELOC_OP_PREL, place, val & ~0xfff, 0, 21,
- AARCH64_INSN_IMM_ADR)) {
+ AARCH64_INSN_IMM_ADR, early)) {
insn = le32_to_cpu(*place);
insn &= ~BIT(31);
} else {
@@ -253,7 +262,10 @@ static int reloc_insn_adrp(struct module *mod, Elf64_Shdr *sechdrs,
AARCH64_INSN_BRANCH_NOLINK);
}
- *place = cpu_to_le32(insn);
+ if (early)
+ *place = cpu_to_le32(insn);
+ else
+ aarch64_insn_write(place, insn);
return 0;
}
@@ -270,6 +282,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
void *loc;
u64 val;
Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
+ bool early = me->state == MODULE_STATE_UNFORMED;
for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
/* loc corresponds to P in the AArch64 ELF document. */
@@ -322,88 +335,88 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
fallthrough;
case R_AARCH64_MOVW_UABS_G0:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, early);
break;
case R_AARCH64_MOVW_UABS_G1_NC:
overflow_check = false;
fallthrough;
case R_AARCH64_MOVW_UABS_G1:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, early);
break;
case R_AARCH64_MOVW_UABS_G2_NC:
overflow_check = false;
fallthrough;
case R_AARCH64_MOVW_UABS_G2:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, early);
break;
case R_AARCH64_MOVW_UABS_G3:
/* We're using the top bits so we can't overflow. */
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 48,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, early);
break;
case R_AARCH64_MOVW_SABS_G0:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, early);
break;
case R_AARCH64_MOVW_SABS_G1:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, early);
break;
case R_AARCH64_MOVW_SABS_G2:
ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, early);
break;
case R_AARCH64_MOVW_PREL_G0_NC:
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, early);
break;
case R_AARCH64_MOVW_PREL_G0:
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, early);
break;
case R_AARCH64_MOVW_PREL_G1_NC:
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, early);
break;
case R_AARCH64_MOVW_PREL_G1:
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, early);
break;
case R_AARCH64_MOVW_PREL_G2_NC:
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
- AARCH64_INSN_IMM_MOVKZ);
+ AARCH64_INSN_IMM_MOVKZ, early);
break;
case R_AARCH64_MOVW_PREL_G2:
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, early);
break;
case R_AARCH64_MOVW_PREL_G3:
/* We're using the top bits so we can't overflow. */
overflow_check = false;
ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 48,
- AARCH64_INSN_IMM_MOVNZ);
+ AARCH64_INSN_IMM_MOVNZ, early);
break;
/* Immediate instruction relocations. */
case R_AARCH64_LD_PREL_LO19:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
- AARCH64_INSN_IMM_19);
+ AARCH64_INSN_IMM_19, early);
break;
case R_AARCH64_ADR_PREL_LO21:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 0, 21,
- AARCH64_INSN_IMM_ADR);
+ AARCH64_INSN_IMM_ADR, early);
break;
case R_AARCH64_ADR_PREL_PG_HI21_NC:
overflow_check = false;
fallthrough;
case R_AARCH64_ADR_PREL_PG_HI21:
- ovf = reloc_insn_adrp(me, sechdrs, loc, val);
+ ovf = reloc_insn_adrp(me, sechdrs, loc, val, early);
if (ovf && ovf != -ERANGE)
return ovf;
break;
@@ -411,40 +424,40 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
case R_AARCH64_LDST8_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 0, 12,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, early);
break;
case R_AARCH64_LDST16_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 1, 11,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, early);
break;
case R_AARCH64_LDST32_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 2, 10,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, early);
break;
case R_AARCH64_LDST64_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 3, 9,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, early);
break;
case R_AARCH64_LDST128_ABS_LO12_NC:
overflow_check = false;
ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 4, 8,
- AARCH64_INSN_IMM_12);
+ AARCH64_INSN_IMM_12, early);
break;
case R_AARCH64_TSTBR14:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 14,
- AARCH64_INSN_IMM_14);
+ AARCH64_INSN_IMM_14, early);
break;
case R_AARCH64_CONDBR19:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
- AARCH64_INSN_IMM_19);
+ AARCH64_INSN_IMM_19, early);
break;
case R_AARCH64_JUMP26:
case R_AARCH64_CALL26:
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26,
- AARCH64_INSN_IMM_26);
+ AARCH64_INSN_IMM_26, early);
if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
ovf == -ERANGE) {
@@ -452,7 +465,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
if (!val)
return -ENOEXEC;
ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2,
- 26, AARCH64_INSN_IMM_26);
+ 26, AARCH64_INSN_IMM_26, early);
}
break;
--
2.17.1
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