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Date: Mon, 27 Oct 2014 18:19:12 -0700
From: Stephen Boyd <sboyd@...eaurora.org>
To: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
Russell King <linux@....linux.org.uk>,
Måns Rullgård <mans@...sr.com>,
Will Deacon <will.deacon@....com>,
Mark Rutland <mark.rutland@....com>
Subject: [RFC/PATCH] ARM: Expose cpuid registers to userspace
Exporting all the different possible configurations of CPUID
registers to userspace via hwcaps is going to explode the hwcaps.
Emulate userspace cpuid register accesses and export a new
"cpuid" hwcap instead so that userspace can know to try to
read the cpuid registers itself.
Cc: Måns Rullgård <mans@...sr.com>
Cc: Will Deacon <will.deacon@....com>
Cc: Mark Rutland <mark.rutland@....com>
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
---
This is in response to Will's suggestion[1] that we explore exposing
these cpuid registers to userspace. A simple test program is as follows:
#include <stdio.h>
int main(void)
{
int val;
__asm__ volatile ("mrc p15, 0, %0, c0, c1, 0\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c1, 0 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c1, 1\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c1, 1 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c1, 2\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c1, 2 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c1, 3\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c1, 3 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c1, 4\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c1, 4 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c1, 5\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c1, 5 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c1, 6\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c1, 6 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c1, 7\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c1, 7 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c2, 0\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c2, 0 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c2, 1\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c2, 1 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c2, 2\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c2, 2 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c2, 3\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c2, 3 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c2, 4\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c2, 4 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c2, 5\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c2, 5 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c2, 6\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c2, 6 is %#x\n", val);
__asm__ volatile ("mrc p15, 0, %0, c0, c2, 7\n" : "=r" (val));
fprintf(stderr, "mrc p15, 0, rX, c0, c2, 7 is %#x\n", val);
__asm__ volatile ("mrc p10, 7, %0, c7, c0, 0\n" : "=r" (val));
fprintf(stderr, "mrc p10, 0, rX, c7, c0, 0 is %#x\n", val);
__asm__ volatile ("mrc p10, 7, %0, c6, c0, 0\n" : "=r" (val));
fprintf(stderr, "mrc p10, 0, rX, c6, c0, 0 is %#x\n", val);
__asm__ volatile ("mrc p10, 7, %0, c0, c0, 0\n" : "=r" (val));
fprintf(stderr, "mrc p10, 0, rX, c0, c0, 0 is %#x\n", val);
__asm__ volatile ("mrc p10, 7, %0, c2, c0, 0\n" : "=r" (val));
return 0;
}
[1] http://lkml.kernel.org/r/20141027103118.GA8768@arm.com
arch/arm/include/asm/opcodes.h | 9 +++
arch/arm/include/uapi/asm/hwcap.h | 1 +
arch/arm/kernel/setup.c | 113 +++++++++++++++++++++++++++++++++++++-
arch/arm/kernel/swp_emulate.c | 8 ---
4 files changed, 122 insertions(+), 9 deletions(-)
diff --git a/arch/arm/include/asm/opcodes.h b/arch/arm/include/asm/opcodes.h
index e796c598513b..751eca1d4e22 100644
--- a/arch/arm/include/asm/opcodes.h
+++ b/arch/arm/include/asm/opcodes.h
@@ -216,6 +216,15 @@ extern asmlinkage unsigned int arm_check_condition(u32 opcode, u32 psr);
#define __inst_arm_thumb32(arm_opcode, thumb_opcode) __inst_arm(arm_opcode)
#endif
+/*
+ * Macros/defines for extracting register numbers from instruction.
+ */
+#define EXTRACT_REG_NUM(instruction, offset) \
+ (((instruction) & (0xf << (offset))) >> (offset))
+#define RN_OFFSET 16
+#define RT_OFFSET 12
+#define RT2_OFFSET 0
+
/* Helpers for the helpers. Don't use these directly. */
#ifdef __ASSEMBLY__
#define ___inst_arm(x) .long x
diff --git a/arch/arm/include/uapi/asm/hwcap.h b/arch/arm/include/uapi/asm/hwcap.h
index 20d12f230a2f..4ec061e81d38 100644
--- a/arch/arm/include/uapi/asm/hwcap.h
+++ b/arch/arm/include/uapi/asm/hwcap.h
@@ -27,6 +27,7 @@
#define HWCAP_IDIV (HWCAP_IDIVA | HWCAP_IDIVT)
#define HWCAP_LPAE (1 << 20)
#define HWCAP_EVTSTRM (1 << 21)
+#define HWCAP_CPUID (1 << 22)
/*
* HWCAP2 flags - for elf_hwcap2 (in kernel) and AT_HWCAP2
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 84db893dedc2..ea0c1a013e00 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -30,6 +30,7 @@
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/sort.h>
+#include <linux/perf_event.h>
#include <asm/unified.h>
#include <asm/cp15.h>
@@ -56,9 +57,11 @@
#include <asm/unwind.h>
#include <asm/memblock.h>
#include <asm/virt.h>
+#include <asm/opcodes.h>
+#include <asm/vfp.h>
#include "atags.h"
-
+#include "../vfp/vfpinstr.h"
#if defined(CONFIG_FPE_NWFPE) || defined(CONFIG_FPE_FASTFPE)
char fpe_type[8];
@@ -371,6 +374,108 @@ void __init early_print(const char *str, ...)
printk("%s", buf);
}
+static u32 arm_id_registers[2 * 8];
+static u32 arm_vfp_id_registers[3];
+
+static void cache_id_registers(void)
+{
+ arm_id_registers[0] = read_cpuid_ext(CPUID_EXT_PFR0);
+ arm_id_registers[1] = read_cpuid_ext(CPUID_EXT_PFR1);
+ arm_id_registers[2] = read_cpuid_ext(CPUID_EXT_DFR0);
+ arm_id_registers[3] = read_cpuid_ext(CPUID_EXT_AFR0);
+ arm_id_registers[4] = read_cpuid_ext(CPUID_EXT_MMFR0);
+ arm_id_registers[5] = read_cpuid_ext(CPUID_EXT_MMFR1);
+ arm_id_registers[6] = read_cpuid_ext(CPUID_EXT_MMFR2);
+ arm_id_registers[7] = read_cpuid_ext(CPUID_EXT_MMFR3);
+ arm_id_registers[8] = read_cpuid_ext(CPUID_EXT_ISAR0);
+ arm_id_registers[9] = read_cpuid_ext(CPUID_EXT_ISAR1);
+ arm_id_registers[10] = read_cpuid_ext(CPUID_EXT_ISAR2);
+ arm_id_registers[11] = read_cpuid_ext(CPUID_EXT_ISAR3);
+ arm_id_registers[12] = read_cpuid_ext(CPUID_EXT_ISAR4);
+ arm_id_registers[13] = read_cpuid_ext(CPUID_EXT_ISAR5);
+ arm_vfp_id_registers[0] = fmrx(FPSID);
+ arm_vfp_id_registers[1] = fmrx(MVFR1);
+ arm_vfp_id_registers[2] = fmrx(MVFR0);
+}
+
+static int get_id_trap(struct pt_regs *regs, unsigned int instr)
+{
+ unsigned int destreg, crm, opc2;
+ unsigned int res;
+
+ perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc);
+
+ res = arm_check_condition(instr, regs->ARM_cpsr);
+ if (res == ARM_OPCODE_CONDTEST_FAIL) {
+ regs->ARM_pc += 4;
+ return 0;
+ }
+
+ destreg = EXTRACT_REG_NUM(instr, RT_OFFSET);
+ crm = instr & 0xf;
+ opc2 = (instr >> 5) & 0x7;
+
+ if (crm > 2 || crm == 0)
+ return -EINVAL;
+
+ regs->uregs[destreg] = arm_id_registers[((crm - 1) * 8) + opc2];
+ regs->ARM_pc += 4;
+
+ return 0;
+}
+
+struct undef_hook arm_mrc_id_hook = {
+ .instr_mask = 0x0f100f10,
+ .instr_val = 0x0e100f10,
+ .cpsr_mask = MODE_MASK,
+ .cpsr_val = USR_MODE,
+ .fn = get_id_trap,
+};
+
+static int get_vmrs_id_trap(struct pt_regs *regs, unsigned int instr)
+{
+ unsigned int destreg, data, reg;
+ unsigned int res;
+
+ perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc);
+
+ res = arm_check_condition(instr, regs->ARM_cpsr);
+ if (res == ARM_OPCODE_CONDTEST_FAIL) {
+ regs->ARM_pc += 4;
+ return 0;
+ }
+
+ destreg = EXTRACT_REG_NUM(instr, RT_OFFSET);
+ reg = (instr >> 16) & 0xf;
+
+ switch (reg) {
+ case 0:
+ data = arm_vfp_id_registers[0];
+ break;
+ case 6:
+ data = arm_vfp_id_registers[1];
+ break;
+ case 7:
+ data = arm_vfp_id_registers[2];
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ regs->uregs[destreg] = data;
+ regs->ARM_pc += 4;
+
+ return 0;
+}
+
+struct undef_hook arm_vmrs_id_hook = {
+ .instr_mask = 0x0ff00ff0,
+ .instr_val = 0x0ef00a10,
+ .cpsr_mask = MODE_MASK,
+ .cpsr_val = USR_MODE,
+ .fn = get_vmrs_id_trap,
+};
+
static void __init cpuid_init_hwcaps(void)
{
unsigned int divide_instrs, vmsa;
@@ -378,6 +483,11 @@ static void __init cpuid_init_hwcaps(void)
if (cpu_architecture() < CPU_ARCH_ARMv7)
return;
+ cache_id_registers();
+ elf_hwcap |= HWCAP_CPUID;
+ register_undef_hook(&arm_mrc_id_hook);
+ register_undef_hook(&arm_vmrs_id_hook);
+
divide_instrs = (read_cpuid_ext(CPUID_EXT_ISAR0) & 0x0f000000) >> 24;
switch (divide_instrs) {
@@ -1009,6 +1119,7 @@ static const char *hwcap_str[] = {
"vfpd32",
"lpae",
"evtstrm",
+ "cpuid",
NULL
};
diff --git a/arch/arm/kernel/swp_emulate.c b/arch/arm/kernel/swp_emulate.c
index 67ca8578c6d8..ebdcac50feef 100644
--- a/arch/arm/kernel/swp_emulate.c
+++ b/arch/arm/kernel/swp_emulate.c
@@ -62,14 +62,6 @@
__user_swpX_asm(data, addr, res, temp, "b")
/*
- * Macros/defines for extracting register numbers from instruction.
- */
-#define EXTRACT_REG_NUM(instruction, offset) \
- (((instruction) & (0xf << (offset))) >> (offset))
-#define RN_OFFSET 16
-#define RT_OFFSET 12
-#define RT2_OFFSET 0
-/*
* Bit 22 of the instruction encoding distinguishes between
* the SWP and SWPB variants (bit set means SWPB).
*/
--
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a Linux Foundation Collaborative Project
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