Re: [PATCH v3 1/3] RISC-V: Correctly print supported extensions

Heiko Stübner
2022-02-14T20:04:25Z

Am Samstag, 12. Februar 2022, 07:29:59 CET schrieb Tsukasa OI:
> This commit replaces BITS_PER_LONG with number of alphabet letters.
>
> Current ISA pretty-printing code expects extension 'a' (bit 0) through
> 'z' (bit 25). Although bit 26 and higher is not currently used (thus never
> cause an issue in practice), it will be an annoying problem if we start to
> use those in the future.
>
> This commit disables printing high bits for now.
>
> Signed-off-by: Tsukasa OI <research_trasio@irq.a4lg.com>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>

Tested-by: Heiko Stuebner <heiko@sntech.de>

> ---
> arch/riscv/kernel/cpufeature.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index d959d207a40d..dd3d57eb4eea 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -13,6 +13,8 @@
> #include <asm/smp.h>
> #include <asm/switch_to.h>
>
> +#define NUM_ALPHA_EXTS ('z' - 'a' + 1)
> +
> unsigned long elf_hwcap __read_mostly;
>
> /* Host ISA bitmap */
> @@ -63,7 +65,7 @@ void __init riscv_fill_hwcap(void)
> {
> struct device_node *node;
> const char *isa;
> - char print_str[BITS_PER_LONG + 1];
> + char print_str[NUM_ALPHA_EXTS + 1];
> size_t i, j, isa_len;
> static unsigned long isa2hwcap[256] = {0};
>
> @@ -133,13 +135,13 @@ void __init riscv_fill_hwcap(void)
> }
>
> memset(print_str, 0, sizeof(print_str));
> - for (i = 0, j = 0; i < BITS_PER_LONG; i++)
> + for (i = 0, j = 0; i < NUM_ALPHA_EXTS; i++)
> if (riscv_isa[0] & BIT_MASK(i))
> print_str[j++] = (char)('a' + i);
> pr_info("riscv: ISA extensions %s\n", print_str);
>
> memset(print_str, 0, sizeof(print_str));
> - for (i = 0, j = 0; i < BITS_PER_LONG; i++)
> + for (i = 0, j = 0; i < NUM_ALPHA_EXTS; i++)
> if (elf_hwcap & BIT_MASK(i))
> print_str[j++] = (char)('a' + i);
> pr_info("riscv: ELF capabilities %s\n", print_str);
>
> base-commit: 7aed1489bdf879da403e8ee9d6d77b0be26bb84d