From 3639d6619c249acf3b8ecc4fd4552486f217dec0 Mon Sep 17 00:00:00 2001 From: "Naveen N. Rao" Date: Thu, 29 Jun 2017 23:19:18 +0530 Subject: [PATCH] powerpc/64s: Un-blacklist system_call() from kprobes 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. Suggested-by: Michael Ellerman Reviewed-by: Nicholas Piggin Signed-off-by: Naveen N. Rao Signed-off-by: Michael Ellerman --- arch/powerpc/kernel/entry_64.S | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index e5cf98d755db..ed45e86673c0 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -188,6 +188,18 @@ system_call: /* label this so stack traces look sane */ andi. r10,r8,MSR_RI beq- unrecov_restore #endif + +/* + * This is a few instructions into the actual syscall exit path (which actually + * starts at .Lsyscall_exit) to cater to kprobe blacklisting and to reduce the + * number of visible symbols for profiling purposes. + * + * We can probe from system_call until this point as MSR_RI is set. But once it + * is cleared below, we won't be able to take a trap. + * + * This is blacklisted from kprobes further below with _ASM_NOKPROBE_SYMBOL(). + */ +system_call_exit: /* * Disable interrupts so current_thread_info()->flags can't change, * and so that we don't get interrupted after loading SRR0/1. @@ -414,7 +426,7 @@ 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) -- 2.20.1