linux-kernel - Re: [PATCH v3 05/18] arm/crc32: expose CRC32 functions through lib

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Message-ID: <20241104181026.GC1049313@google.com>
Date: Mon, 4 Nov 2024 18:10:26 +0000
From: Eric Biggers <ebiggers@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-crypto@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net, linux-mips@...r.kernel.org,
	linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
	linux-scsi@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	loongarch@...ts.linux.dev, sparclinux@...r.kernel.org,
	x86@...nel.org, Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH v3 05/18] arm/crc32: expose CRC32 functions through lib

On Sun, Nov 03, 2024 at 02:31:41PM -0800, Eric Biggers wrote:
> -static int __init crc32_pmull_mod_init(void)
> -{
> -	if (elf_hwcap2 & HWCAP2_PMULL) {
> -		crc32_pmull_algs[0].update = crc32_pmull_update;
> -		crc32_pmull_algs[1].update = crc32c_pmull_update;
> -
> -		if (elf_hwcap2 & HWCAP2_CRC32) {
> -			fallback_crc32 = crc32_armv8_le;
> -			fallback_crc32c = crc32c_armv8_le;
> -		} else {
> -			fallback_crc32 = crc32_le;
> -			fallback_crc32c = __crc32c_le;
> -		}
> -	} else if (!(elf_hwcap2 & HWCAP2_CRC32)) {
> -		return -ENODEV;
> -	}
[...]
> +static u32 crc32_le_scalar(u32 crc, const u8 *p, size_t len)
> +{
> +	if (static_branch_likely(&have_crc32))
> +		return crc32_armv8_le(crc, p, len);
> +	return crc32_le_base(crc, p, len);
> +}

kernel test robot reported a build error on this patch,
"undefined symbol: __kcfi_typeid_crc32_armv8_le".  It's because crc32-core.S
uses SYM_TYPED_FUNC_START(crc32_armv8_le), and this patch makes crc32_armv8_le
be called only via direct calls, not indirect calls as it was before.  I will
fix this by replacing SYM_TYPED_FUNC_START by SYM_FUNC_START.

- Eric