Re: [PATCH] riscv: cpufeature: use bitmap_equal() instead of memcmp()

From: Alexandre Ghiti
Date: Tue Feb 11 2025 - 02:41:54 EST


Hi Clément,

On 10/02/2025 16:56, Clément Léger wrote:
Comparison of bitmaps should be done using bitmap_equal(), not memcmp(),
use the former one to compare isa bitmaps.

Signed-off-by: Clément Léger <cleger@xxxxxxxxxxxx>
---
arch/riscv/kernel/cpufeature.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index c6ba750536c3..40ac72e407b6 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -479,7 +479,7 @@ static void __init riscv_resolve_isa(unsigned long *source_isa,
if (bit < RISCV_ISA_EXT_BASE)
*this_hwcap |= isa2hwcap[bit];
}
- } while (loop && memcmp(prev_resolved_isa, resolved_isa, sizeof(prev_resolved_isa)));
+ } while (loop && !bitmap_equal(prev_resolved_isa, resolved_isa, RISCV_ISA_EXT_MAX));
}
static void __init match_isa_ext(const char *name, const char *name_end, unsigned long *bitmap)


Since bitmap does not guarantee the value of the 'extra' bits (https://elixir.bootlin.com/linux/v6.13.1/source/lib/bitmap.c#L24), this is a fix so I would add a Fixes tag:

Fixes: 625034abd52a8c ("riscv: add ISA extensions validation callback")

You can also add:

Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>

Thanks,

Alex