[PATCH v3] riscv: KGDB: Do not inline arch_kgdb_breakpoint()

[Alexandre Ghiti]

Hi WangYuli,

On 08/04/2025 11:54, WangYuli wrote:
> The arch_kgdb_breakpoint() function defines the kgdb_compiled_break
> symbol using inline assembly.
>
> There's a potential issue where the compiler might inline
> arch_kgdb_breakpoint(), which would then define the kgdb_breakinst


You forgot to replace kgdb_breakinst into kgdb_compiled_break.


> symbol multiple times, leading to fail to link vmlinux.o.
>
> This isn't merely a potential compilation problem. The intent here
> is to determine the global symbol address of kgdb_compiled_break,
> and if this function is inlined multiple times, it would logically
> be a grave error.
>
> Link: https://lore.kernel.org/all/4b4187c1-77e5-44b7-885f-d6826723dd9a@sifive.com/
> Fixes: fe89bd2be866 ("riscv: Add KGDB support")
> Co-developed-by: Huacai Chen <chenhuacai at loongson.cn>
> Signed-off-by: Huacai Chen <chenhuacai at loongson.cn>
> Signed-off-by: WangYuli <wangyuli at uniontech.com>
> ---
> Changelog:
>   *v1->v2:
>      1. Add the missing __ASSEMBLY__ check and substitute
> ".option rvc/norvc" with ".option push/pop".
>    v2->v3:
>      1. Remove "extern".
>      2. Restore the inadvertently deleted .option norvc to prevent
> a change in semantics.
> ---
>   arch/riscv/include/asm/kgdb.h | 9 +--------
>   arch/riscv/kernel/kgdb.c      | 9 +++++++++
>   2 files changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/arch/riscv/include/asm/kgdb.h b/arch/riscv/include/asm/kgdb.h
> index 46677daf708b..cc11c4544cff 100644
> --- a/arch/riscv/include/asm/kgdb.h
> +++ b/arch/riscv/include/asm/kgdb.h
> @@ -19,16 +19,9 @@
>   
>   #ifndef	__ASSEMBLY__
>   
> +void arch_kgdb_breakpoint(void);
>   extern unsigned long kgdb_compiled_break;
>   
> -static inline void arch_kgdb_breakpoint(void)
> -{
> -	asm(".global kgdb_compiled_break\n"
> -	    ".option norvc\n"
> -	    "kgdb_compiled_break: ebreak\n"
> -	    ".option rvc\n");
> -}
> -
>   #endif /* !__ASSEMBLY__ */
>   
>   #define DBG_REG_ZERO "zero"
> diff --git a/arch/riscv/kernel/kgdb.c b/arch/riscv/kernel/kgdb.c
> index 2e0266ae6bd7..7f2d3d956167 100644
> --- a/arch/riscv/kernel/kgdb.c
> +++ b/arch/riscv/kernel/kgdb.c
> @@ -254,6 +254,15 @@ void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
>   	regs->epc = pc;
>   }
>   
> +noinline void arch_kgdb_breakpoint(void)
> +{
> +	asm(".global kgdb_compiled_break\n"
> +	    ".option push\n"
> +	    ".option norvc\n"
> +	    "kgdb_compiled_break: ebreak\n"
> +	    ".option pop\n");
> +}


You are fixing 2 things here, you need to split this patch into 2. And 
as noted by Palmer, we actually don't need norvc here, so you can remove 
it instead.

Thanks,

Alex


> +
>   void kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer,
>   				char *remcom_out_buffer)
>   {