On Mon, 13 Jul 2020 16:39:18 PDT (-0700), guoren@xxxxxxxxxx wrote:
From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> The "Changing Execution Path" section in the Documentation/kprobes.txt said: Since kprobes can probe into a running kernel code, it can change the register set, including instruction pointer. Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx> --- 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)
So that's definately not going to be EPC any more. I'm not sure that field is sanely named, though, as it's really just the PC when it comes to other ptrace stuff.
@@ -157,6 +158,7 @@ ENDPROC(ftrace_caller) .endm .macro RESTORE_ALL + ld ra, PT_EPC(sp) ld x1, PT_RA(sp)
x1 is ra, so loading it twice doesn't seem reasonable.
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) .endm
If you're dropping the load you should drop the store above as well. In general this seems kind of mixed up, both before and after this patch.
