diff options
| author | Andy Polyakov <appro@openssl.org> | 2014-10-30 20:24:29 +0100 |
|---|---|---|
| committer | Andy Polyakov <appro@openssl.org> | 2014-10-30 20:24:29 +0100 |
| commit | 6696203963ba209fbbef12098e6eb6f364379c65 (patch) | |
| tree | 909bec6d72acb0055b3e91cfec3600e23dfcbffa /crypto/armv4cpuid.S | |
| parent | ecb9966e7c44896cf04ab577d4a5d27c9c5ddfac (diff) | |
armv4cpuid.S: fix compilation error in pre-ARMv7 build.
PR: 3474
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
Diffstat (limited to 'crypto/armv4cpuid.S')
| -rw-r--r-- | crypto/armv4cpuid.S | 29 |
1 files changed, 23 insertions, 6 deletions
diff --git a/crypto/armv4cpuid.S b/crypto/armv4cpuid.S index add11d405e..0059311303 100644 --- a/crypto/armv4cpuid.S +++ b/crypto/armv4cpuid.S @@ -3,6 +3,25 @@ .text .code 32 +@ Special note about using .byte directives to encode instructions. +@ Initial reason for hand-coding instructions was to allow module to +@ be compilable by legacy tool-chains. At later point it was pointed +@ out that since ARMv7, instructions are always encoded in little-endian +@ order, therefore one has to opt for endian-neutral presentation. +@ Contemporary tool-chains offer .inst directive for this purpose, +@ but not legacy ones. Therefore .byte. But there is an exception, +@ namely ARMv7-R profile still allows for big-endian encoding even for +@ instructions. This raises the question what if probe instructions +@ appear executable to such processor operating in big-endian order? +@ They have to be chosen in a way that avoids this problem. As failed +@ NEON probe disables a number of other probes we have to ensure that +@ only NEON probe instruction doesn't appear executable in big-endian +@ order, therefore 'vorr q8,q8,q8', and not some other register. The +@ only probe that is not bypassed on failed NEON probe is _armv7_tick, +@ where you'll spot 'mov r0,r6' that serves this purpose. Basic idea is +@ that if fetched in alternative byte oder instruction should crash to +@ denote lack of probed capability... + .align 5 .global _armv7_neon_probe .type _armv7_neon_probe,%function @@ -14,12 +33,10 @@ _armv7_neon_probe: .global _armv7_tick .type _armv7_tick,%function _armv7_tick: - mrrc p15,1,r0,r1,c14 @ CNTVCT -#if __ARM_ARCH__>=5 - bx lr -#else - .word 0xe12fff1e @ bx lr -#endif + .byte 0x06,0x00,0xa0,0xe1 @ mov r0,r6 + .byte 0x1e,0x0f,0x51,0xec @ mrrc p15,1,r0,r1,c14 @ CNTVCT + .byte 0x1e,0xff,0x2f,0xe1 @ bx lr + nop .size _armv7_tick,.-_armv7_tick .global _armv8_aes_probe |