linux-kernel - [PATCH 11/12] powerpc/entry32: Blacklist syscall exit points for kprobe.

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Date:   Sun, 29 Mar 2020 09:41:11 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        naveen.n.rao@...ux.vnet.ibm.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 11/12] powerpc/entry32: Blacklist syscall exit points for
 kprobe.

kprobe does not handle events happening in real mode.

The very last part of syscall cannot support a trap.
Add a symbol syscall_exit_finish to identify that part and
blacklist it from kprobe.

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/kernel/entry_32.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 9a1a45d6038a..7035e838d422 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -463,6 +463,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
 	lwz	r7,_NIP(r1)
 	lwz	r2,GPR2(r1)
 	lwz	r1,GPR1(r1)
+syscall_exit_finish:
 #if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS)
 	mtspr	SPRN_NRI, r0
 #endif
@@ -470,6 +471,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
 	mtspr	SPRN_SRR1,r8
 	SYNC
 	RFI
+_ASM_NOKPROBE_SYMBOL(syscall_exit_finish)
 #ifdef CONFIG_44x
 2:	li	r7,0
 	iccci	r0,r0
@@ -604,6 +606,7 @@ ret_from_kernel_syscall:
 	mtspr	SPRN_SRR1, r10
 	SYNC
 	RFI
+_ASM_NOKPROBE_SYMBOL(ret_from_kernel_syscall)
 
 /*
  * The fork/clone functions need to copy the full register set into
-- 
2.25.0