linux-kernel - Re: [PATCH] ARM: kprobes: Make __kretprobe

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Date:   Thu, 24 Mar 2022 14:34:46 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>, kbuild-all@...ts.01.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm function

--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -377,7 +377,7 @@ void __naked __kprobes __kretprobe_trampoline(void)
 {
        __asm__ __volatile__ (
 #ifdef CONFIG_FRAME_POINTER
-               "ldr    lr, =__kretprobe_trampoline     \n\t"
+               "ldr    lr, .L__kretprobe_trampoline    \n\t"
        /* __kretprobe_trampoline makes a framepointer on pt_regs. */
 #ifdef CONFIG_CC_IS_CLANG
                "stmdb  sp, {sp, lr, pc}        \n\t"
@@ -407,6 +407,11 @@ void __naked __kprobes __kretprobe_trampoline(void)
                "bx     lr                      \n\t"
 #else
                "mov    pc, lr                  \n\t"
+#endif
+#ifdef CONFIG_FRAME_POINTER
+               ".align 2                       \n\t"
+       ".L__kretprobe_trampoline:              \n\t"
+               ".long  __kretprobe_trampoline  \n\t"
 #endif
                : : : "memory");
 }


On Thu, 24 Mar 2022 at 14:23, Masami Hiramatsu <mhiramat@...nel.org> wrote:
>
> On Thu, 24 Mar 2022 15:21:08 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
>
> > Hi,
> >
> > I found a better solution for this issue from Ard :-)
> >
> > https://lore.kernel.org/all/20220203082204.1176734-6-ardb@kernel.org/T/#u
> >
> > I should use mov_l instead of ldr for loading the symbol address.
>
> Hm, these macros are only for the pure assembly file (.S), so we have to
> split this in a asm file to use that.
>


What about the below?