When FL_SAVE_REGS is not set we get here via ftrace_caller()
which doesn't save all registers.
ftrace_caller() explicitely clears regs.msr, so we can rely
on it to know where we come from. We don't expect MSR register
to be 0 at all when involving ftrace.
Reported-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
Fixes: 40b035efe288 ("powerpc/ftrace: Implement
CONFIG_DYNAMIC_FTRACE_WITH_ARGS")
Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
arch/powerpc/include/asm/ftrace.h | 3 ++-
arch/powerpc/kernel/trace/ftrace_mprofile.S | 4 ++++
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/ftrace.h
b/arch/powerpc/include/asm/ftrace.h
index 70b457097098..ff034ae4e472 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -30,7 +30,8 @@ struct ftrace_regs {
static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs
*fregs)
{
- return &fregs->regs;
+ /* We clear regs.msr in ftrace_call */
+ return fregs->regs.msr ? &fregs->regs : NULL;
}
static __always_inline void ftrace_instruction_pointer_set(struct ftrace_regs
*fregs,
diff --git a/arch/powerpc/kernel/trace/ftrace_mprofile.S
b/arch/powerpc/kernel/trace/ftrace_mprofile.S
index 8443902d5a05..eb077270ec2f 100644
--- a/arch/powerpc/kernel/trace/ftrace_mprofile.S
+++ b/arch/powerpc/kernel/trace/ftrace_mprofile.S
@@ -205,6 +205,10 @@ _GLOBAL(ftrace_caller)
PPC_STL r0, _LINK(r1)
mr r4, r0
+ /* Clear MSR to flag as ftrace_caller versus frace_regs_caller */
+ li r8, 0
+ PPC_STL r8, _MSR(r1)
+
/* Load &pt_regs in r6 for call below */
addi r6, r1 ,STACK_FRAME_OVERHEAD
--
2.34.1
