ARM: perf: add support for perf registers API

This patch implements the functions required for the perf registers API,
allowing the perf tool to interface kernel register dumps with libunwind
in order to provide userspace backtracing.

Cc: Jean Pihet <jean.pihet@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

5 files changed, 57 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 1ad6fb6c094d..899d0c6ec2c5 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -51,6 +51,8 @@ config ARM
         select HAVE_MOD_ARCH_SPECIFIC if ARM_UNWIND
         select HAVE_OPROFILE if (HAVE_PERF_EVENTS)
         select HAVE_PERF_EVENTS
+        select HAVE_PERF_REGS
+        select HAVE_PERF_USER_STACK_DUMP
         select HAVE_REGS_AND_STACK_ACCESS_API
         select HAVE_SYSCALL_TRACEPOINTS
         select HAVE_UID16
diff --git a/arch/arm/include/uapi/asm/Kbuild b/arch/arm/include/uapi/asm/Kbuild
index 18d76fd5a2af..70a1c9da30ca 100644
--- a/arch/arm/include/uapi/asm/Kbuild
+++ b/arch/arm/include/uapi/asm/Kbuild
@@ -7,6 +7,7 @@ header-y += hwcap.h
 header-y += ioctls.h
 header-y += kvm_para.h
 header-y += mman.h
+header-y += perf_regs.h
 header-y += posix_types.h
 header-y += ptrace.h
 header-y += setup.h
diff --git a/arch/arm/include/uapi/asm/perf_regs.h b/arch/arm/include/uapi/asm/perf_regs.h
new file mode 100644
index 000000000000..ce59448458b2
--- /dev/null
+++ b/arch/arm/include/uapi/asm/perf_regs.h
@@ -0,0 +1,23 @@
+#ifndef _ASM_ARM_PERF_REGS_H
+#define _ASM_ARM_PERF_REGS_H
+
+enum perf_event_arm_regs {
+        PERF_REG_ARM_R0,
+        PERF_REG_ARM_R1,
+        PERF_REG_ARM_R2,
+        PERF_REG_ARM_R3,
+        PERF_REG_ARM_R4,
+        PERF_REG_ARM_R5,
+        PERF_REG_ARM_R6,
+        PERF_REG_ARM_R7,
+        PERF_REG_ARM_R8,
+        PERF_REG_ARM_R9,
+        PERF_REG_ARM_R10,
+        PERF_REG_ARM_FP,
+        PERF_REG_ARM_IP,
+        PERF_REG_ARM_SP,
+        PERF_REG_ARM_LR,
+        PERF_REG_ARM_PC,
+        PERF_REG_ARM_MAX,
+};
+#endif /* _ASM_ARM_PERF_REGS_H */
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 5140df5f23aa..9b818ca3610b 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -78,6 +78,7 @@ obj-$(CONFIG_CPU_XSC3)		+= xscale-cp0.o
 obj-$(CONFIG_CPU_MOHAWK)        += xscale-cp0.o
 obj-$(CONFIG_CPU_PJ4)           += pj4-cp0.o
 obj-$(CONFIG_IWMMXT)            += iwmmxt.o
+obj-$(CONFIG_PERF_EVENTS)       += perf_regs.o
 obj-$(CONFIG_HW_PERF_EVENTS)    += perf_event.o perf_event_cpu.o
 AFLAGS_iwmmxt.o                 := -Wa,-mcpu=iwmmxt
 obj-$(CONFIG_ARM_CPU_TOPOLOGY)  += topology.o
diff --git a/arch/arm/kernel/perf_regs.c b/arch/arm/kernel/perf_regs.c
new file mode 100644
index 000000000000..6e4379c67cbc
--- /dev/null
+++ b/arch/arm/kernel/perf_regs.c
@@ -0,0 +1,30 @@
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/perf_event.h>
+#include <linux/bug.h>
+#include <asm/perf_regs.h>
+#include <asm/ptrace.h>
+
+u64 perf_reg_value(struct pt_regs *regs, int idx)
+{
+        if (WARN_ON_ONCE((u32)idx >= PERF_REG_ARM_MAX))
+                return 0;
+
+        return regs->uregs[idx];
+}
+
+#define REG_RESERVED (~((1ULL << PERF_REG_ARM_MAX) - 1))
+
+int perf_reg_validate(u64 mask)
+{
+        if (!mask || mask & REG_RESERVED)
+                return -EINVAL;
+
+        return 0;
+}
+
+u64 perf_reg_abi(struct task_struct *task)
+{
+        return PERF_SAMPLE_REGS_ABI_32;
+}