It is actually safe to probe system_call() in entry_64.S, but only till
we unset MSR_RI. To allow this, add a new symbol system_call_exit()
after the mtmsrd and blacklist that. Though the mtmsrd instruction
itself is now whitelisted, we won't be allowed to probe on it as we
don't allow probing on rfi and mtmsr instructions (checked for in
arch_prepare_kprobe()).
Suggested-by: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
---
arch/powerpc/kernel/entry_64.S | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index ef8e6615b8ba..feeeadc9aa71 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -204,6 +204,7 @@ system_call: /* label this so stack
traces look sane */
mtmsrd r11,1
#endif /* CONFIG_PPC_BOOK3E */
+system_call_exit:
ld r9,TI_FLAGS(r12)
li r11,-MAX_ERRNO
andi.
r0,r9,(_TIF_SYSCALL_DOTRACE|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)
@@ -412,7 +413,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
b . /* prevent speculative execution */
#endif
_ASM_NOKPROBE_SYMBOL(system_call_common);
-_ASM_NOKPROBE_SYMBOL(system_call);
+_ASM_NOKPROBE_SYMBOL(system_call_exit);
/* Save non-volatile GPRs, if not already saved. */
_GLOBAL(save_nvgprs)
--
2.13.1
