Hi,
when working with the Linaro patches I found that a particular commit breaks our aarch64 kernel build.
The patch in question is that one:
commit be09330da9d0777c4a58568d137e3f8a3dbe0a0b Author: Yvan Roux yvan.roux@linaro.org Date: Tue Oct 27 21:18:19 2015 +0100
One of the things it attempts to change apparently is moving the .arch specifiers in the assembler file from a global scope to individual functions. What also happens though is that they seem to lose some information after that transformation.
I observed that when building arch/arm64/crypto/aes-ce-cipher.c from the Linux kernel. This code contains inline assembly like this:
static void aes_cipher_decrypt(struct crypto_tfm *tfm, u8 dst[], u8 const src[]) { struct crypto_aes_ctx *ctx = crypto_tfm_ctx(tfm); struct aes_block *out = (struct aes_block *)dst; struct aes_block const *in = (struct aes_block *)src; void *dummy0; int dummy1;
kernel_neon_begin_partial(4);
__asm__(" ld1 {v0.16b}, %[in] ;" " ld1 {v1.2d}, [%[key]], #16 ;" " cmp %w[rounds], #10 ;" " bmi 0f ;" " bne 3f ;" " mov v3.16b, v1.16b ;" " b 2f ;" "0: mov v2.16b, v1.16b ;" " ld1 {v3.2d}, [%[key]], #16 ;" "1: aesd v0.16b, v2.16b ;" " aesimc v0.16b, v0.16b ;" "2: ld1 {v1.2d}, [%[key]], #16 ;" " aesd v0.16b, v3.16b ;" " aesimc v0.16b, v0.16b ;" "3: ld1 {v2.2d}, [%[key]], #16 ;" " subs %w[rounds], %w[rounds], #3 ;" " aesd v0.16b, v1.16b ;" " aesimc v0.16b, v0.16b ;" " ld1 {v3.2d}, [%[key]], #16 ;" " bpl 1b ;" " aesd v0.16b, v2.16b ;" " eor v0.16b, v0.16b, v3.16b ;" " st1 {v0.16b}, %[out] ;"
: [out] "=Q"(*out), [key] "=r"(dummy0), [rounds] "=r"(dummy1) : [in] "Q"(*in), "1"(ctx->key_dec), "2"(num_rounds(ctx) - 2) : "cc");
kernel_neon_end(); }
Now without this patch the compiler behaved like the following. It was invoked with:
aarch64-linux-gnu-gcc -Wp,-MD,arch/arm64/crypto/.aes-ce-cipher.o.d -nostdinc -isystem /var/fpwork/rschiele/crossbuild/builds/aarch64-linux-gnu/linux-next/srcdir/bin/../lib/gcc/aarch64-linux-gnu/5.2.1/include -I/var/fpwork/rschiele/crossbuild/builds/aarch64-linux-gnu/linux-next/srcdir/src/linux/arch/arm64/include -Iarch/arm64/include/generated/uapi -Iarch/arm64/include/generated -I/var/fpwork/rschiele/crossbuild/builds/aarch64-linux-gnu/linux-next/srcdir/src/linux/include -Iinclude -I/var/fpwork/rschiele/crossbuild/builds/aarch64-linux-gnu/linux-next/srcdir/src/linux/arch/arm64/include/uapi -Iarch/arm64/include/generated/uapi -I/var/fpwork/rschiele/crossbuild/builds/aarch64-linux-gnu/linux-next/srcdir/src/linux/include/uapi -Iinclude/generated/uapi -include /var/fpwork/rschiele/crossbuild/builds/aarch64-linux-gnu/linux-next/srcdir/src/linux/include/linux/kconfig.h -I/var/fpwork/rschiele/crossbuild/builds/aarch64-linux-gnu/linux-next/srcdir/src/linux/arch/arm64/crypto -Iarch/arm64/crypto -D__KERNEL__ -mlittle-endian -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -std=gnu89 -mgeneral-regs-only -fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0 -Wframe-larger-than=2048 -fno-stack-protector -Wno-unused-but-set-variable -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-var-tracking-assignments -g -Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow -fconserve-stack -Werror=implicit-int -Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO -Werror -march=armv8-a+crypto -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(aes_ce_cipher)" -D"KBUILD_MODNAME=KBUILD_STR(aes_ce_cipher)" -c -o arch/arm64/crypto/aes-ce-cipher.o /var/fpwork/rschiele/crossbuild/builds/aarch64-linux-gnu/linux-next/srcdir/src/linux/arch/arm64/crypto/aes-ce-cipher.c
As a result it created a file for the assembler with the global
.arch armv8-a+fp+simd+crypto
at the beginning of the file.
After the patch it created individual
.arch armv8-a
at individual places.
It is not clear to me, why the extensions (fp+simd+crypto) got lost. Is that intended, such that the code needs special adaption for inline assembly using those extensions or is that loss of extensions a bug of that patch?
Greetings! Robert