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[PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm function

Masami Hiramatsu posted 1 patch 4 years, 3 months ago 
arch/arm/probes/kprobes/core.c |   57 +++++++++++++++++++++-------------------
1 file changed, 30 insertions(+), 27 deletions(-)
[PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm function
Posted by Masami Hiramatsu 4 years, 3 months ago 
Make __kretprobe_trampoline() as a pure asm function same as the x86
code does. Anyway, it is safe to define the symbol in the asm code
instead of accessing a C symbol from the inline asm.

Without this fix, building arm kernel with GCC-11 may cause below
error.

   /tmp/ccIWiggX.s: Assembler messages:
>> /tmp/ccIWiggX.s:22: Error: invalid literal constant: pool needs to be closer

This fixes the error reported by 0day build bot.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 7e9bf33b8124 ("ARM: kprobes: Make a frame pointer on __kretprobe_trampoline")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/arm/probes/kprobes/core.c |   57 +++++++++++++++++++++-------------------
 1 file changed, 30 insertions(+), 27 deletions(-)

diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
index 4848404ba51b..51f1438456ae 100644
--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -373,43 +373,46 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
  * should be enough for stacktrace from the return handler with or
  * without pt_regs.
  */
-void __naked __kprobes __kretprobe_trampoline(void)
-{
-	__asm__ __volatile__ (
+asm(
+	".text\n"
+	".global __kretprobe_trampoline\n"
+	".type __kretprobe_trampoline, %function\n"
+	"__kretprobe_trampoline:\n"
 #ifdef CONFIG_FRAME_POINTER
-		"ldr	lr, =__kretprobe_trampoline	\n\t"
+	"ldr	lr, =__kretprobe_trampoline	\n\t"
 	/* __kretprobe_trampoline makes a framepointer on pt_regs. */
 #ifdef CONFIG_CC_IS_CLANG
-		"stmdb	sp, {sp, lr, pc}	\n\t"
-		"sub	sp, sp, #12		\n\t"
-		/* In clang case, pt_regs->ip = lr. */
-		"stmdb	sp!, {r0 - r11, lr}	\n\t"
-		/* fp points regs->r11 (fp) */
-		"add	fp, sp,	#44		\n\t"
+	"stmdb	sp, {sp, lr, pc}	\n\t"
+	"sub	sp, sp, #12		\n\t"
+	/* In clang case, pt_regs->ip = lr. */
+	"stmdb	sp!, {r0 - r11, lr}	\n\t"
+	/* fp points regs->r11 (fp) */
+	"add	fp, sp,	#44		\n\t"
 #else /* !CONFIG_CC_IS_CLANG */
-		/* In gcc case, pt_regs->ip = fp. */
-		"stmdb	sp, {fp, sp, lr, pc}	\n\t"
-		"sub	sp, sp, #16		\n\t"
-		"stmdb	sp!, {r0 - r11}		\n\t"
-		/* fp points regs->r15 (pc) */
-		"add	fp, sp, #60		\n\t"
+	/* In gcc case, pt_regs->ip = fp. */
+	"stmdb	sp, {fp, sp, lr, pc}	\n\t"
+	"sub	sp, sp, #16		\n\t"
+	"stmdb	sp!, {r0 - r11}		\n\t"
+	/* fp points regs->r15 (pc) */
+	"add	fp, sp, #60		\n\t"
 #endif /* CONFIG_CC_IS_CLANG */
 #else /* !CONFIG_FRAME_POINTER */
-		"sub	sp, sp, #16		\n\t"
-		"stmdb	sp!, {r0 - r11}		\n\t"
+	"sub	sp, sp, #16		\n\t"
+	"stmdb	sp!, {r0 - r11}		\n\t"
 #endif /* CONFIG_FRAME_POINTER */
-		"mov	r0, sp			\n\t"
-		"bl	trampoline_handler	\n\t"
-		"mov	lr, r0			\n\t"
-		"ldmia	sp!, {r0 - r11}		\n\t"
-		"add	sp, sp, #16		\n\t"
+	"mov	r0, sp			\n\t"
+	"bl	trampoline_handler	\n\t"
+	"mov	lr, r0			\n\t"
+	"ldmia	sp!, {r0 - r11}		\n\t"
+	"add	sp, sp, #16		\n\t"
 #ifdef CONFIG_THUMB2_KERNEL
-		"bx	lr			\n\t"
+	"bx	lr			\n\t"
 #else
-		"mov	pc, lr			\n\t"
+	"mov	pc, lr			\n\t"
 #endif
-		: : : "memory");
-}
+	".size __kretprobe_trampoline, .-__kretprobe_trampoline\n"
+);
+NOKPROBE_SYMBOL(__kretprobe_trampoline);
 
 /* Called from __kretprobe_trampoline */
 static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
Re: [PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm function
Posted by Masami Hiramatsu 4 years, 3 months ago 
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.

Thank you,

On Tue, 15 Mar 2022 18:52:16 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Make __kretprobe_trampoline() as a pure asm function same as the x86
> code does. Anyway, it is safe to define the symbol in the asm code
> instead of accessing a C symbol from the inline asm.
> 
> Without this fix, building arm kernel with GCC-11 may cause below
> error.
> 
>    /tmp/ccIWiggX.s: Assembler messages:
> >> /tmp/ccIWiggX.s:22: Error: invalid literal constant: pool needs to be closer
> 
> This fixes the error reported by 0day build bot.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Fixes: 7e9bf33b8124 ("ARM: kprobes: Make a frame pointer on __kretprobe_trampoline")
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  arch/arm/probes/kprobes/core.c |   57 +++++++++++++++++++++-------------------
>  1 file changed, 30 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
> index 4848404ba51b..51f1438456ae 100644
> --- a/arch/arm/probes/kprobes/core.c
> +++ b/arch/arm/probes/kprobes/core.c
> @@ -373,43 +373,46 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
>   * should be enough for stacktrace from the return handler with or
>   * without pt_regs.
>   */
> -void __naked __kprobes __kretprobe_trampoline(void)
> -{
> -	__asm__ __volatile__ (
> +asm(
> +	".text\n"
> +	".global __kretprobe_trampoline\n"
> +	".type __kretprobe_trampoline, %function\n"
> +	"__kretprobe_trampoline:\n"
>  #ifdef CONFIG_FRAME_POINTER
> -		"ldr	lr, =__kretprobe_trampoline	\n\t"
> +	"ldr	lr, =__kretprobe_trampoline	\n\t"
>  	/* __kretprobe_trampoline makes a framepointer on pt_regs. */
>  #ifdef CONFIG_CC_IS_CLANG
> -		"stmdb	sp, {sp, lr, pc}	\n\t"
> -		"sub	sp, sp, #12		\n\t"
> -		/* In clang case, pt_regs->ip = lr. */
> -		"stmdb	sp!, {r0 - r11, lr}	\n\t"
> -		/* fp points regs->r11 (fp) */
> -		"add	fp, sp,	#44		\n\t"
> +	"stmdb	sp, {sp, lr, pc}	\n\t"
> +	"sub	sp, sp, #12		\n\t"
> +	/* In clang case, pt_regs->ip = lr. */
> +	"stmdb	sp!, {r0 - r11, lr}	\n\t"
> +	/* fp points regs->r11 (fp) */
> +	"add	fp, sp,	#44		\n\t"
>  #else /* !CONFIG_CC_IS_CLANG */
> -		/* In gcc case, pt_regs->ip = fp. */
> -		"stmdb	sp, {fp, sp, lr, pc}	\n\t"
> -		"sub	sp, sp, #16		\n\t"
> -		"stmdb	sp!, {r0 - r11}		\n\t"
> -		/* fp points regs->r15 (pc) */
> -		"add	fp, sp, #60		\n\t"
> +	/* In gcc case, pt_regs->ip = fp. */
> +	"stmdb	sp, {fp, sp, lr, pc}	\n\t"
> +	"sub	sp, sp, #16		\n\t"
> +	"stmdb	sp!, {r0 - r11}		\n\t"
> +	/* fp points regs->r15 (pc) */
> +	"add	fp, sp, #60		\n\t"
>  #endif /* CONFIG_CC_IS_CLANG */
>  #else /* !CONFIG_FRAME_POINTER */
> -		"sub	sp, sp, #16		\n\t"
> -		"stmdb	sp!, {r0 - r11}		\n\t"
> +	"sub	sp, sp, #16		\n\t"
> +	"stmdb	sp!, {r0 - r11}		\n\t"
>  #endif /* CONFIG_FRAME_POINTER */
> -		"mov	r0, sp			\n\t"
> -		"bl	trampoline_handler	\n\t"
> -		"mov	lr, r0			\n\t"
> -		"ldmia	sp!, {r0 - r11}		\n\t"
> -		"add	sp, sp, #16		\n\t"
> +	"mov	r0, sp			\n\t"
> +	"bl	trampoline_handler	\n\t"
> +	"mov	lr, r0			\n\t"
> +	"ldmia	sp!, {r0 - r11}		\n\t"
> +	"add	sp, sp, #16		\n\t"
>  #ifdef CONFIG_THUMB2_KERNEL
> -		"bx	lr			\n\t"
> +	"bx	lr			\n\t"
>  #else
> -		"mov	pc, lr			\n\t"
> +	"mov	pc, lr			\n\t"
>  #endif
> -		: : : "memory");
> -}
> +	".size __kretprobe_trampoline, .-__kretprobe_trampoline\n"
> +);
> +NOKPROBE_SYMBOL(__kretprobe_trampoline);
>  
>  /* Called from __kretprobe_trampoline */
>  static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>
Re: [PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm function
Posted by Masami Hiramatsu 4 years, 3 months ago 
On Thu, 24 Mar 2022 15:21:08 +0900
Masami Hiramatsu <mhiramat@kernel.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.

Thanks,

> 
> Thank you,
> 
> On Tue, 15 Mar 2022 18:52:16 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
> 
> > Make __kretprobe_trampoline() as a pure asm function same as the x86
> > code does. Anyway, it is safe to define the symbol in the asm code
> > instead of accessing a C symbol from the inline asm.
> > 
> > Without this fix, building arm kernel with GCC-11 may cause below
> > error.
> > 
> >    /tmp/ccIWiggX.s: Assembler messages:
> > >> /tmp/ccIWiggX.s:22: Error: invalid literal constant: pool needs to be closer
> > 
> > This fixes the error reported by 0day build bot.
> > 
> > Reported-by: kernel test robot <lkp@intel.com>
> > Fixes: 7e9bf33b8124 ("ARM: kprobes: Make a frame pointer on __kretprobe_trampoline")
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > ---
> >  arch/arm/probes/kprobes/core.c |   57 +++++++++++++++++++++-------------------
> >  1 file changed, 30 insertions(+), 27 deletions(-)
> > 
> > diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
> > index 4848404ba51b..51f1438456ae 100644
> > --- a/arch/arm/probes/kprobes/core.c
> > +++ b/arch/arm/probes/kprobes/core.c
> > @@ -373,43 +373,46 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
> >   * should be enough for stacktrace from the return handler with or
> >   * without pt_regs.
> >   */
> > -void __naked __kprobes __kretprobe_trampoline(void)
> > -{
> > -	__asm__ __volatile__ (
> > +asm(
> > +	".text\n"
> > +	".global __kretprobe_trampoline\n"
> > +	".type __kretprobe_trampoline, %function\n"
> > +	"__kretprobe_trampoline:\n"
> >  #ifdef CONFIG_FRAME_POINTER
> > -		"ldr	lr, =__kretprobe_trampoline	\n\t"
> > +	"ldr	lr, =__kretprobe_trampoline	\n\t"
> >  	/* __kretprobe_trampoline makes a framepointer on pt_regs. */
> >  #ifdef CONFIG_CC_IS_CLANG
> > -		"stmdb	sp, {sp, lr, pc}	\n\t"
> > -		"sub	sp, sp, #12		\n\t"
> > -		/* In clang case, pt_regs->ip = lr. */
> > -		"stmdb	sp!, {r0 - r11, lr}	\n\t"
> > -		/* fp points regs->r11 (fp) */
> > -		"add	fp, sp,	#44		\n\t"
> > +	"stmdb	sp, {sp, lr, pc}	\n\t"
> > +	"sub	sp, sp, #12		\n\t"
> > +	/* In clang case, pt_regs->ip = lr. */
> > +	"stmdb	sp!, {r0 - r11, lr}	\n\t"
> > +	/* fp points regs->r11 (fp) */
> > +	"add	fp, sp,	#44		\n\t"
> >  #else /* !CONFIG_CC_IS_CLANG */
> > -		/* In gcc case, pt_regs->ip = fp. */
> > -		"stmdb	sp, {fp, sp, lr, pc}	\n\t"
> > -		"sub	sp, sp, #16		\n\t"
> > -		"stmdb	sp!, {r0 - r11}		\n\t"
> > -		/* fp points regs->r15 (pc) */
> > -		"add	fp, sp, #60		\n\t"
> > +	/* In gcc case, pt_regs->ip = fp. */
> > +	"stmdb	sp, {fp, sp, lr, pc}	\n\t"
> > +	"sub	sp, sp, #16		\n\t"
> > +	"stmdb	sp!, {r0 - r11}		\n\t"
> > +	/* fp points regs->r15 (pc) */
> > +	"add	fp, sp, #60		\n\t"
> >  #endif /* CONFIG_CC_IS_CLANG */
> >  #else /* !CONFIG_FRAME_POINTER */
> > -		"sub	sp, sp, #16		\n\t"
> > -		"stmdb	sp!, {r0 - r11}		\n\t"
> > +	"sub	sp, sp, #16		\n\t"
> > +	"stmdb	sp!, {r0 - r11}		\n\t"
> >  #endif /* CONFIG_FRAME_POINTER */
> > -		"mov	r0, sp			\n\t"
> > -		"bl	trampoline_handler	\n\t"
> > -		"mov	lr, r0			\n\t"
> > -		"ldmia	sp!, {r0 - r11}		\n\t"
> > -		"add	sp, sp, #16		\n\t"
> > +	"mov	r0, sp			\n\t"
> > +	"bl	trampoline_handler	\n\t"
> > +	"mov	lr, r0			\n\t"
> > +	"ldmia	sp!, {r0 - r11}		\n\t"
> > +	"add	sp, sp, #16		\n\t"
> >  #ifdef CONFIG_THUMB2_KERNEL
> > -		"bx	lr			\n\t"
> > +	"bx	lr			\n\t"
> >  #else
> > -		"mov	pc, lr			\n\t"
> > +	"mov	pc, lr			\n\t"
> >  #endif
> > -		: : : "memory");
> > -}
> > +	".size __kretprobe_trampoline, .-__kretprobe_trampoline\n"
> > +);
> > +NOKPROBE_SYMBOL(__kretprobe_trampoline);
> >  
> >  /* Called from __kretprobe_trampoline */
> >  static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
> > 
> 
> 
> -- 
> Masami Hiramatsu <mhiramat@kernel.org>


-- 
Masami Hiramatsu <mhiramat@kernel.org>
Re: [PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm function
Posted by Ard Biesheuvel 4 years, 3 months ago 
--- 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@kernel.org> wrote:
>
> On Thu, 24 Mar 2022 15:21:08 +0900
> Masami Hiramatsu <mhiramat@kernel.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?
Re: [PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm function
Posted by Ard Biesheuvel 4 years, 3 months ago 
On Thu, 24 Mar 2022 at 14:34, Ard Biesheuvel <ardb@kernel.org> wrote:
>
> --- 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");
>  }
>
>

Pardon the copy/paste error.

> What about the below?

was meant to refer to the diff above.


> On Thu, 24 Mar 2022 at 14:23, Masami Hiramatsu <mhiramat@kernel.org> wrote:
> >
> > On Thu, 24 Mar 2022 15:21:08 +0900
> > Masami Hiramatsu <mhiramat@kernel.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?
Re: [PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm function
Posted by Masami Hiramatsu 4 years, 3 months ago 
Hi Ard,

On Thu, 24 Mar 2022 14:34:46 +0100
Ard Biesheuvel <ardb@kernel.org> wrote:

> --- 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");
>  }

Yes, I confirmed this works too :-)

Can you send the patch with my Tested-by ?

Thank you!

> 
> 
> On Thu, 24 Mar 2022 at 14:23, Masami Hiramatsu <mhiramat@kernel.org> wrote:
> >
> > On Thu, 24 Mar 2022 15:21:08 +0900
> > Masami Hiramatsu <mhiramat@kernel.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?


-- 
Masami Hiramatsu <mhiramat@kernel.org>

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