Hi Linus,
On Mon, Jun 10, 2024 at 01:48:20PM -0700, Linus Torvalds wrote:
> This generates noticeably better code with compilers that support it,
> since we don't need to test the error register etc, the exception just
> jumps to the error handling directly.
>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> ---
> arch/arm64/include/asm/uaccess.h | 77 +++++++++++++++++++-------------
> 1 file changed, 46 insertions(+), 31 deletions(-)
>
> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
> index 23c2edf517ed..4ab3938290ab 100644
> --- a/arch/arm64/include/asm/uaccess.h
> +++ b/arch/arm64/include/asm/uaccess.h
> @@ -294,29 +294,41 @@ do { \
> } while (0); \
> } while (0)
>
> -#define __put_mem_asm(store, reg, x, addr, err, type) \
> +#ifdef CONFIG_CC_HAS_ASM_GOTO
This symbol was eliminated two years ago with commit a0a12c3ed057 ("asm
goto: eradicate CC_HAS_ASM_GOTO") since all supported compilers have
support for it.
> +#define __put_mem_asm(store, reg, x, addr, label, type) \
> + asm goto( \
> + "1: " store " " reg "0, [%1]\n" \
> + "2:\n" \
> + _ASM_EXTABLE_##type##ACCESS_ZERO(1b, %l2) \
> + : : "rZ" (x), "r" (addr) : : label)
> +#else
> +#define __put_mem_asm(store, reg, x, addr, label, type) do { \
> + int __pma_err = 0; \
> asm volatile( \
> "1: " store " " reg "1, [%2]\n" \
> "2:\n" \
> _ASM_EXTABLE_##type##ACCESS_ERR(1b, 2b, %w0) \
> - : "+r" (err) \
> - : "rZ" (x), "r" (addr))
> + : "+r" (__pma_err) \
> + : "rZ" (x), "r" (addr)); \
> + if (__pma_err) goto label; \
> +} while (0)
> +#endif
Cheers,
Nathan
