3 files changed, 61 insertions, 0 deletions

diff --git a/tools/perf/arch/arm/Makefile b/tools/perf/arch/arm/Makefile
index 67e9b3d38e89..9b8f87e8c7b9 100644
--- a/tools/perf/arch/arm/Makefile
+++ b/tools/perf/arch/arm/Makefile
@@ -4,4 +4,5 @@ LIB_OBJS += $(OUTPUT)arch/$(ARCH)/util/dwarf-regs.o
 endif
 ifndef NO_LIBUNWIND
 LIB_OBJS += $(OUTPUT)arch/$(ARCH)/util/unwind-libunwind.o
+LIB_OBJS += $(OUTPUT)arch/$(ARCH)/tests/regs_load.o
 endif
diff --git a/tools/perf/arch/arm/include/perf_regs.h b/tools/perf/arch/arm/include/perf_regs.h
index bcca511f5884..33abcfa3057c 100644
--- a/tools/perf/arch/arm/include/perf_regs.h
+++ b/tools/perf/arch/arm/include/perf_regs.h
@@ -5,6 +5,8 @@
 #include <linux/types.h>
 #include <asm/perf_regs.h>
 
+void perf_regs_load(u64 *regs);
+
 #define PERF_REGS_MASK  ((1ULL << PERF_REG_ARM_MAX) - 1)
 #define PERF_REG_IP     PERF_REG_ARM_PC
 #define PERF_REG_SP     PERF_REG_ARM_SP
diff --git a/tools/perf/arch/arm/tests/regs_load.S b/tools/perf/arch/arm/tests/regs_load.S
new file mode 100644
index 000000000000..e09e983946fe
--- /dev/null
+++ b/tools/perf/arch/arm/tests/regs_load.S
@@ -0,0 +1,58 @@
+#include <linux/linkage.h>
+
+#define R0 0x00
+#define R1 0x08
+#define R2 0x10
+#define R3 0x18
+#define R4 0x20
+#define R5 0x28
+#define R6 0x30
+#define R7 0x38
+#define R8 0x40
+#define R9 0x48
+#define SL 0x50
+#define FP 0x58
+#define IP 0x60
+#define SP 0x68
+#define LR 0x70
+#define PC 0x78
+
+/*
+ * Implementation of void perf_regs_load(u64 *regs);
+ *
+ * This functions fills in the 'regs' buffer from the actual registers values,
+ * in the way the perf built-in unwinding test expects them:
+ * - the PC at the time at the call to this function. Since this function
+ *   is called using a bl instruction, the PC value is taken from LR.
+ * The built-in unwinding test then unwinds the call stack from the dwarf
+ * information in unwind__get_entries.
+ *
+ * Notes:
+ * - the 8 bytes stride in the registers offsets comes from the fact
+ * that the registers are stored in an u64 array (u64 *regs),
+ * - the regs buffer needs to be zeroed before the call to this function,
+ * in this case using a calloc in dwarf-unwind.c.
+ */
+
+.text
+.type perf_regs_load,%function
+ENTRY(perf_regs_load)
+        str r0, [r0, #R0]
+        str r1, [r0, #R1]
+        str r2, [r0, #R2]
+        str r3, [r0, #R3]
+        str r4, [r0, #R4]
+        str r5, [r0, #R5]
+        str r6, [r0, #R6]
+        str r7, [r0, #R7]
+        str r8, [r0, #R8]
+        str r9, [r0, #R9]
+        str sl, [r0, #SL]
+        str fp, [r0, #FP]
+        str ip, [r0, #IP]
+        str sp, [r0, #SP]
+        str lr, [r0, #LR]
+        str lr, [r0, #PC]       // store pc as lr in order to skip the call
+                                //  to this function
+        mov pc, lr
+ENDPROC(perf_regs_load)