Adding kprobes on some assembly functions (mainly exception handling)
will result in crashes (either recursive trap or panic). To avoid such
errors, add ASM_NOKPROBE() macro which allow adding specific symbols
into the __kprobe_blacklist section and use to blacklist the following
symbols that showed to be problematic:
- handle_exception()
- ret_from_exception()
- handle_kernel_stack_overflow()
Signed-off-by: Clément Léger <[email protected]>
---
arch/riscv/include/asm/asm.h | 10 ++++++++++
arch/riscv/kernel/entry.S | 3 +++
2 files changed, 13 insertions(+)
diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h
index 114bbadaef41..9194e334de15 100644
--- a/arch/riscv/include/asm/asm.h
+++ b/arch/riscv/include/asm/asm.h
@@ -142,6 +142,16 @@
REG_L x31, PT_T6(sp)
.endm
+/* Annotate a function as being unsuitable for kprobes. */
+#ifdef CONFIG_KPROBES
+#define ASM_NOKPROBE(name) \
+ .pushsection "_kprobe_blacklist", "aw"; \
+ RISCV_PTR name; \
+ .popsection
+#else
+#define ASM_NOKPROBE(name)
+#endif
+
#endif /* __ASSEMBLY__ */
#endif /* _ASM_RISCV_ASM_H */
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 143a2bb3e697..f24bc4eeedde 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -101,6 +101,7 @@ _save_context:
1:
tail do_trap_unknown
SYM_CODE_END(handle_exception)
+ASM_NOKPROBE(handle_exception)
/*
* The ret_from_exception must be called with interrupt disabled. Here is the
@@ -167,6 +168,7 @@ SYM_CODE_START_NOALIGN(ret_from_exception)
sret
#endif
SYM_CODE_END(ret_from_exception)
+ASM_NOKPROBE(ret_from_exception)
#ifdef CONFIG_VMAP_STACK
SYM_CODE_START_LOCAL(handle_kernel_stack_overflow)
@@ -254,6 +256,7 @@ restore_caller_reg:
move a0, sp
tail handle_bad_stack
SYM_CODE_END(handle_kernel_stack_overflow)
+ASM_NOKPROBE(handle_kernel_stack_overflow)
#endif
SYM_CODE_START(ret_from_fork)
--
2.42.0
On Wed, Oct 04, 2023 at 03:10:09PM +0200, Cl?ment L?ger wrote:
> Adding kprobes on some assembly functions (mainly exception handling)
> will result in crashes (either recursive trap or panic). To avoid such
> errors, add ASM_NOKPROBE() macro which allow adding specific symbols
> into the __kprobe_blacklist section and use to blacklist the following
> symbols that showed to be problematic:
> - handle_exception()
> - ret_from_exception()
> - handle_kernel_stack_overflow()
>
> Signed-off-by: Cl?ment L?ger <[email protected]>
> ---
> arch/riscv/include/asm/asm.h | 10 ++++++++++
> arch/riscv/kernel/entry.S | 3 +++
> 2 files changed, 13 insertions(+)
>
> diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h
> index 114bbadaef41..9194e334de15 100644
> --- a/arch/riscv/include/asm/asm.h
> +++ b/arch/riscv/include/asm/asm.h
> @@ -142,6 +142,16 @@
> REG_L x31, PT_T6(sp)
> .endm
>
> +/* Annotate a function as being unsuitable for kprobes. */
> +#ifdef CONFIG_KPROBES
> +#define ASM_NOKPROBE(name) \
> + .pushsection "_kprobe_blacklist", "aw"; \
> + RISCV_PTR name; \
> + .popsection
> +#else
> +#define ASM_NOKPROBE(name)
> +#endif
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* _ASM_RISCV_ASM_H */
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 143a2bb3e697..f24bc4eeedde 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -101,6 +101,7 @@ _save_context:
> 1:
> tail do_trap_unknown
> SYM_CODE_END(handle_exception)
> +ASM_NOKPROBE(handle_exception)
>
> /*
> * The ret_from_exception must be called with interrupt disabled. Here is the
> @@ -167,6 +168,7 @@ SYM_CODE_START_NOALIGN(ret_from_exception)
> sret
> #endif
> SYM_CODE_END(ret_from_exception)
> +ASM_NOKPROBE(ret_from_exception)
>
> #ifdef CONFIG_VMAP_STACK
> SYM_CODE_START_LOCAL(handle_kernel_stack_overflow)
> @@ -254,6 +256,7 @@ restore_caller_reg:
> move a0, sp
> tail handle_bad_stack
> SYM_CODE_END(handle_kernel_stack_overflow)
> +ASM_NOKPROBE(handle_kernel_stack_overflow)
> #endif
>
> SYM_CODE_START(ret_from_fork)
> --
> 2.42.0
>
>
> _______________________________________________
> linux-riscv mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-riscv
Reviewed-by: Charlie Jenkins <[email protected]>
Hello:
This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <[email protected]>:
On Wed, 4 Oct 2023 15:10:09 +0200 you wrote:
> Adding kprobes on some assembly functions (mainly exception handling)
> will result in crashes (either recursive trap or panic). To avoid such
> errors, add ASM_NOKPROBE() macro which allow adding specific symbols
> into the __kprobe_blacklist section and use to blacklist the following
> symbols that showed to be problematic:
> - handle_exception()
> - ret_from_exception()
> - handle_kernel_stack_overflow()
>
> [...]
Here is the summary with links:
- riscv: blacklist assembly symbols for kprobe
https://git.kernel.org/riscv/c/5014396af9bb
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html