[PATCH v3 3/7] riscv: Fixup kprobes handler couldn't change pc

guoren at kernel.org guoren at kernel.org
Mon Jul 13 19:39:18 EDT 2020

From: Guo Ren <guoren at linux.alibaba.com>

The "Changing Execution Path" section in the Documentation/kprobes.txt

Since kprobes can probe into a running kernel code, it can change the
register set, including instruction pointer.

Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
Cc: Masami Hiramatsu <mhiramat at kernel.org>
Cc: Palmer Dabbelt <palmerdabbelt at google.com>
 arch/riscv/kernel/mcount-dyn.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index 35a6ed7..4b58b54 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -123,6 +123,7 @@ ENDPROC(ftrace_caller)
 	sd	ra, (PT_SIZE_ON_STACK+8)(sp)
 	addi	s0, sp, (PT_SIZE_ON_STACK+16)
+	sd ra,  PT_EPC(sp)
 	sd x1,  PT_RA(sp)
 	sd x2,  PT_SP(sp)
 	sd x3,  PT_GP(sp)
@@ -157,6 +158,7 @@ ENDPROC(ftrace_caller)
 	.macro RESTORE_ALL
+	ld ra,  PT_EPC(sp)
 	ld x1,  PT_RA(sp)
 	ld x2,  PT_SP(sp)
 	ld x3,  PT_GP(sp)
@@ -190,7 +192,6 @@ ENDPROC(ftrace_caller)
 	ld x31, PT_T6(sp)
 	ld	s0, (PT_SIZE_ON_STACK)(sp)
-	ld	ra, (PT_SIZE_ON_STACK+8)(sp)
 	addi	sp, sp, (PT_SIZE_ON_STACK+16)

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