[PATCH v4 5/7] powerpc/64s: Un-blacklist system_call() from kprobes

Naveen N. Rao naveen.n.rao at linux.vnet.ibm.com
Thu Jun 29 20:41:08 AEST 2017


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 <mpe at ellerman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n.rao at 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 c39436706555..7a87427a67cd 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -205,6 +205,7 @@ 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)
@@ -413,7 +414,7 @@ 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



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