Messages in this thread Patch in this message | | | From | Luca Barbieri <> | Subject | [PATCH 03/10] x86: add support for lock prefix in alternatives | Date | Wed, 17 Feb 2010 12:42:35 +0100 |
| |
The current lock prefix UP/SMP alternative code doesn't allow LOCK_PREFIX to be used in alternatives code.
This patch solves the problem by adding a new LOCK_PREFIX_ALTERNATIVE_PATCH macro that only records the lock prefix location but does not emit the prefix.
The user of this macro can then start any alternative sequence with "lock" and have it UP/SMP patched.
To make this work, the UP/SMP alternative code is changed to do the lock/DS prefix switching only if the byte actually contains a lock or DS prefix.
Thus, if an alternative without the "lock" is selected, it will now do nothing instead of clobbering the code.
Signed-off-by: Luca Barbieri <luca@luca-barbieri.com> --- arch/x86/include/asm/alternative.h | 6 ++++-- arch/x86/kernel/alternative.c | 6 ++++-- 2 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index 42d41ac..b31af51 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -28,12 +28,14 @@ */ #ifdef CONFIG_SMP -#define LOCK_PREFIX \ +#define LOCK_PREFIX_ALTERNATIVE_PATCH \ ".section .smp_locks,\"a\"\n" \ _ASM_ALIGN "\n" \ _ASM_PTR "661f\n" /* address */ \ ".previous\n" \ - "661:\n\tlock; " + "661:" + +#define LOCK_PREFIX LOCK_PREFIX_ALTERNATIVE_PATCH "\n\tlock; " #else /* ! CONFIG_SMP */ #define LOCK_PREFIX "" diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 7464c7e..b4ff6cb 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -264,7 +264,8 @@ static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end) if (*ptr > text_end) continue; /* turn DS segment override prefix into lock prefix */ - text_poke(*ptr, ((unsigned char []){0xf0}), 1); + if (**ptr == 0x3e) + text_poke(*ptr, ((unsigned char []){0xf0}), 1); }; mutex_unlock(&text_mutex); } @@ -283,7 +284,8 @@ static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end if (*ptr > text_end) continue; /* turn lock prefix into DS segment override prefix */ - text_poke(*ptr, ((unsigned char []){0x3E}), 1); + if (**ptr == 0xf0) + text_poke(*ptr, ((unsigned char []){0x3E}), 1); }; mutex_unlock(&text_mutex); } -- 1.6.6.1.476.g01ddb
| |