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-rw-r--r--arch/powerpc/kernel/misc.S26
1 files changed, 26 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S
index 2d29752cbe16..22e507c8a556 100644
--- a/arch/powerpc/kernel/misc.S
+++ b/arch/powerpc/kernel/misc.S
@@ -127,3 +127,29 @@ _GLOBAL(__setup_cpu_power7)
_GLOBAL(__restore_cpu_power7)
/* place holder */
blr
+
+/*
+ * Get a minimal set of registers for our caller's nth caller.
+ * r3 = regs pointer, r5 = n.
+ *
+ * We only get R1 (stack pointer), NIP (next instruction pointer)
+ * and LR (link register). These are all we can get in the
+ * general case without doing complicated stack unwinding, but
+ * fortunately they are enough to do a stack backtrace, which
+ * is all we need them for.
+ */
+_GLOBAL(perf_arch_fetch_caller_regs)
+ mr r6,r1
+ cmpwi r5,0
+ mflr r4
+ ble 2f
+ mtctr r5
+1: PPC_LL r6,0(r6)
+ bdnz 1b
+ PPC_LL r4,PPC_LR_STKOFF(r6)
+2: PPC_LL r7,0(r6)
+ PPC_LL r7,PPC_LR_STKOFF(r7)
+ PPC_STL r6,GPR1-STACK_FRAME_OVERHEAD(r3)
+ PPC_STL r4,_NIP-STACK_FRAME_OVERHEAD(r3)
+ PPC_STL r7,_LINK-STACK_FRAME_OVERHEAD(r3)
+ blr