[PATCH] lib: sbi: fix undefined behavior in signed shifts in sbi_hart.c, sbi_ecall_interface.h

[Anup Patel]

On Mon, Feb 23, 2026 at 5:41 AM Marcos Oduardo <marcos.oduardo at gmail.com> wrote:
>
> UBSan detected undefined behavior in sbi_hart.c and sbi_fwft.c (in the case
> of sbi_fwft.c, the bug comes from a macro call defined at sbi_ecall_interface.h)
> caused by shifting a signed integer into the sign bit (1 << 31)
>
> This can be fixed by using the 1UL literal, ensuring defined arithmetic.
>
> Please let me know if there’s any other most suitable solution for this bug.
>
> Signed-off-by: Marcos Oduardo <marcos.oduardo at gmail.com>

The patch subject can be a bit shorter. I have taken care at the
time of merging.

Reviewed-by: Anup Patel <anup at brainfault.org>

Applied this patch to the riscv/opensbi repo.

Thanks,
Anup


> ---
>  include/sbi/sbi_ecall_interface.h | 2 +-
>  lib/sbi/sbi_hart.c                | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/sbi/sbi_ecall_interface.h b/include/sbi/sbi_ecall_interface.h
> index 76624e3f..9a776f79 100644
> --- a/include/sbi/sbi_ecall_interface.h
> +++ b/include/sbi/sbi_ecall_interface.h
> @@ -144,7 +144,7 @@ enum sbi_fwft_feature_t {
>         SBI_FWFT_GLOBAL_PLATFORM_END            = 0xffffffff,
>  };
>
> -#define SBI_FWFT_GLOBAL_FEATURE_BIT            (1 << 31)
> +#define SBI_FWFT_GLOBAL_FEATURE_BIT            (1UL << 31)
>  #define SBI_FWFT_PLATFORM_FEATURE_BIT          (1 << 30)
>
>  #define SBI_FWFT_SET_FLAG_LOCK                 (1 << 0)
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 60e95bca..99e13990 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -70,7 +70,7 @@ static void mstatus_init(struct sbi_scratch *scratch)
>          */
>         mhpmevent_init_val |= (MHPMEVENT_OF | MHPMEVENT_MINH);
>         for (cidx = 0; cidx <= 28; cidx++) {
> -               if (!(mhpm_mask & 1 << (cidx + 3)))
> +               if (!(mhpm_mask & 1UL << (cidx + 3)))
>                         continue;
>  #if __riscv_xlen == 32
>                 csr_write_num(CSR_MHPMEVENT3 + cidx,
> --
> 2.53.0
>
>
> --
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