Re: [PATCH v3 14/15] riscv: Add support for suppressing warning backtraces

Charlie Jenkins
2024-04-22T17:40:58Z

On Wed, Apr 03, 2024 at 06:19:35AM -0700, Guenter Roeck wrote:
> Add name of functions triggering warning backtraces to the __bug_table
> object section to enable support for suppressing WARNING backtraces.
>
> To limit image size impact, the pointer to the function name is only added
> to the __bug_table section if both CONFIG_KUNIT_SUPPRESS_BACKTRACE and
> CONFIG_DEBUG_BUGVERBOSE are enabled. Otherwise, the __func__ assembly
> parameter is replaced with a (dummy) NULL parameter to avoid an image size
> increase due to unused __func__ entries (this is necessary because __func__
> is not a define but a virtual variable).
>
> To simplify the implementation, unify the __BUG_ENTRY_ADDR and
> __BUG_ENTRY_FILE macros into a single macro named __BUG_REL() which takes
> the address, file, or function reference as parameter.
>
> Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
> Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
> Cc: Paul Walmsley <paul.walmsley@sifive.com>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Albert Ou <aou@eecs.berkeley.edu>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> v2:
> - Rebased to v6.9-rc1
> - Added Tested-by:, Acked-by:, and Reviewed-by: tags
> - Introduced KUNIT_SUPPRESS_BACKTRACE configuration option
> v3:
> - Rebased to v6.9-rc2
>
> arch/riscv/include/asm/bug.h | 38 ++++++++++++++++++++++++------------
> 1 file changed, 26 insertions(+), 12 deletions(-)
>
> diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
> index 1aaea81fb141..79f360af4ad8 100644
> --- a/arch/riscv/include/asm/bug.h
> +++ b/arch/riscv/include/asm/bug.h
> @@ -30,26 +30,39 @@
> typedef u32 bug_insn_t;
>
> #ifdef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
> -#define __BUG_ENTRY_ADDR RISCV_INT " 1b - ."
> -#define __BUG_ENTRY_FILE RISCV_INT " %0 - ."
> +#define __BUG_REL(val) RISCV_INT " " __stringify(val) " - ."
> #else
> -#define __BUG_ENTRY_ADDR RISCV_PTR " 1b"
> -#define __BUG_ENTRY_FILE RISCV_PTR " %0"
> +#define __BUG_REL(val) RISCV_PTR " " __stringify(val)
> #endif
>
> #ifdef CONFIG_DEBUG_BUGVERBOSE
> +
> +#ifdef CONFIG_KUNIT_SUPPRESS_BACKTRACE
> +# define HAVE_BUG_FUNCTION
> +# define __BUG_FUNC_PTR __BUG_REL(%1)
> +#else
> +# define __BUG_FUNC_PTR
> +#endif /* CONFIG_KUNIT_SUPPRESS_BACKTRACE */
> +
> #define __BUG_ENTRY \
> - __BUG_ENTRY_ADDR "\n\t" \
> - __BUG_ENTRY_FILE "\n\t" \
> - RISCV_SHORT " %1\n\t" \
> - RISCV_SHORT " %2"
> + __BUG_REL(1b) "\n\t" \
> + __BUG_REL(%0) "\n\t" \
> + __BUG_FUNC_PTR "\n\t" \
> + RISCV_SHORT " %2\n\t" \
> + RISCV_SHORT " %3"
> #else
> #define __BUG_ENTRY \
> - __BUG_ENTRY_ADDR "\n\t" \
> - RISCV_SHORT " %2"
> + __BUG_REL(1b) "\n\t" \
> + RISCV_SHORT " %3"
> #endif
>
> #ifdef CONFIG_GENERIC_BUG
> +#ifdef HAVE_BUG_FUNCTION
> +# define __BUG_FUNC __func__
> +#else
> +# define __BUG_FUNC NULL
> +#endif
> +
> #define __BUG_FLAGS(flags) \
> do { \
> __asm__ __volatile__ ( \
> @@ -58,10 +71,11 @@ do { \
> ".pushsection __bug_table,\"aw\"\n\t" \
> "2:\n\t" \
> __BUG_ENTRY "\n\t" \
> - ".org 2b + %3\n\t" \
> + ".org 2b + %4\n\t" \
> ".popsection" \
> : \
> - : "i" (__FILE__), "i" (__LINE__), \
> + : "i" (__FILE__), "i" (__BUG_FUNC), \
> + "i" (__LINE__), \
> "i" (flags), \
> "i" (sizeof(struct bug_entry))); \
> } while (0)
> --
> 2.39.2
>
>
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Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>

- Charlie