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From:   Christophe Leroy <christophe.leroy@c-s.fr>
Subject: [PATCH v2 12/12] powerpc/entry32: Blacklist exception exit points for
 kprobe.
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        naveen.n.rao@linux.vnet.ibm.com
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Date:   Tue, 31 Mar 2020 16:03:47 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

kprobe does not handle events happening in real mode.

The very last part of exception exits cannot support a trap.
Blacklist them from kprobe.

While we are at it, remove exc_exit_start symbol which is not
used to avoid having to blacklist it.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/entry_32.S | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 577d17fe0d94..02c81192ba52 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -810,6 +810,7 @@ fast_exception_return:
 	lwz	r11,GPR11(r11)
 	SYNC
 	RFI
+_ASM_NOKPROBE_SYMBOL(fast_exception_return)
 
 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
 /* check if the exception happened in a restartable section */
@@ -1049,6 +1050,8 @@ exc_exit_restart:
 exc_exit_restart_end:
 	SYNC
 	RFI
+_ASM_NOKPROBE_SYMBOL(exc_exit_restart)
+_ASM_NOKPROBE_SYMBOL(exc_exit_restart_end)
 
 #else /* !(CONFIG_4xx || CONFIG_BOOKE) */
 	/*
@@ -1070,7 +1073,6 @@ exc_exit_restart_end:
 exc_exit_restart:
 	lwz	r11,_NIP(r1)
 	lwz	r12,_MSR(r1)
-exc_exit_start:
 	mtspr	SPRN_SRR0,r11
 	mtspr	SPRN_SRR1,r12
 	REST_2GPRS(11, r1)
@@ -1080,6 +1082,7 @@ exc_exit_restart_end:
 	PPC405_ERR77_SYNC
 	rfi
 	b	.			/* prevent prefetch past rfi */
+_ASM_NOKPROBE_SYMBOL(exc_exit_restart)
 
 /*
  * Returning from a critical interrupt in user mode doesn't need
@@ -1193,6 +1196,7 @@ ret_from_crit_exc:
 	mtspr	SPRN_SRR0,r9;
 	mtspr	SPRN_SRR1,r10;
 	RET_FROM_EXC_LEVEL(SPRN_CSRR0, SPRN_CSRR1, PPC_RFCI)
+_ASM_NOKPROBE_SYMBOL(ret_from_crit_exc)
 #endif /* CONFIG_40x */
 
 #ifdef CONFIG_BOOKE
@@ -1204,6 +1208,7 @@ ret_from_crit_exc:
 	RESTORE_xSRR(SRR0,SRR1);
 	RESTORE_MMU_REGS;
 	RET_FROM_EXC_LEVEL(SPRN_CSRR0, SPRN_CSRR1, PPC_RFCI)
+_ASM_NOKPROBE_SYMBOL(ret_from_crit_exc)
 
 	.globl	ret_from_debug_exc
 ret_from_debug_exc:
@@ -1214,6 +1219,7 @@ ret_from_debug_exc:
 	RESTORE_xSRR(CSRR0,CSRR1);
 	RESTORE_MMU_REGS;
 	RET_FROM_EXC_LEVEL(SPRN_DSRR0, SPRN_DSRR1, PPC_RFDI)
+_ASM_NOKPROBE_SYMBOL(ret_from_debug_exc)
 
 	.globl	ret_from_mcheck_exc
 ret_from_mcheck_exc:
@@ -1225,6 +1231,7 @@ ret_from_mcheck_exc:
 	RESTORE_xSRR(DSRR0,DSRR1);
 	RESTORE_MMU_REGS;
 	RET_FROM_EXC_LEVEL(SPRN_MCSRR0, SPRN_MCSRR1, PPC_RFMCI)
+_ASM_NOKPROBE_SYMBOL(ret_from_mcheck_exc)
 #endif /* CONFIG_BOOKE */
 
 /*
-- 
2.25.0