diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2023-10-17 19:27:34 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-10-20 13:19:51 +0300 |
| commit | 59bec00ace28d565ae0a68b23063ef3b961d82d5 (patch) | |
| tree | bfe2316d321a1703e7508c438d5290fd9ab30065 /arch/x86/lib/cmpxchg8b_emu.S | |
| parent | aa47f90cd4331e1809d56c72fcbdbbe0a85e5992 (diff) | |
| download | linux-59bec00ace28d565ae0a68b23063ef3b961d82d5.tar.xz | |
x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()
Introduce x86_64 %rip-relative addressing to the PER_CPU_VAR() macro.
Instructions using %rip-relative address operand are one byte shorter
than their absolute address counterparts and are also compatible with
position independent executable (-fpie) builds. The patch reduces
code size of a test kernel build by 150 bytes.
The PER_CPU_VAR() macro is intended to be applied to a symbol and should
not be used with register operands. Introduce the new __percpu macro and
use it in cmpxchg{8,16}b_emu.S instead.
Also add a missing function comment to this_cpu_cmpxchg8b_emu().
No functional changes intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: Brian Gerst <brgerst@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/lib/cmpxchg8b_emu.S')
| -rw-r--r-- | arch/x86/lib/cmpxchg8b_emu.S | 30 |
1 files changed, 21 insertions, 9 deletions
diff --git a/arch/x86/lib/cmpxchg8b_emu.S b/arch/x86/lib/cmpxchg8b_emu.S index 49805257b125..8632d7dd1f00 100644 --- a/arch/x86/lib/cmpxchg8b_emu.S +++ b/arch/x86/lib/cmpxchg8b_emu.S @@ -24,12 +24,12 @@ SYM_FUNC_START(cmpxchg8b_emu) pushfl cli - cmpl 0(%esi), %eax + cmpl (%esi), %eax jne .Lnot_same cmpl 4(%esi), %edx jne .Lnot_same - movl %ebx, 0(%esi) + movl %ebx, (%esi) movl %ecx, 4(%esi) orl $X86_EFLAGS_ZF, (%esp) @@ -38,7 +38,7 @@ SYM_FUNC_START(cmpxchg8b_emu) RET .Lnot_same: - movl 0(%esi), %eax + movl (%esi), %eax movl 4(%esi), %edx andl $(~X86_EFLAGS_ZF), (%esp) @@ -53,18 +53,30 @@ EXPORT_SYMBOL(cmpxchg8b_emu) #ifndef CONFIG_UML +/* + * Emulate 'cmpxchg8b %fs:(%rsi)' + * + * Inputs: + * %esi : memory location to compare + * %eax : low 32 bits of old value + * %edx : high 32 bits of old value + * %ebx : low 32 bits of new value + * %ecx : high 32 bits of new value + * + * Notably this is not LOCK prefixed and is not safe against NMIs + */ SYM_FUNC_START(this_cpu_cmpxchg8b_emu) pushfl cli - cmpl PER_CPU_VAR(0(%esi)), %eax + cmpl __percpu (%esi), %eax jne .Lnot_same2 - cmpl PER_CPU_VAR(4(%esi)), %edx + cmpl __percpu 4(%esi), %edx jne .Lnot_same2 - movl %ebx, PER_CPU_VAR(0(%esi)) - movl %ecx, PER_CPU_VAR(4(%esi)) + movl %ebx, __percpu (%esi) + movl %ecx, __percpu 4(%esi) orl $X86_EFLAGS_ZF, (%esp) @@ -72,8 +84,8 @@ SYM_FUNC_START(this_cpu_cmpxchg8b_emu) RET .Lnot_same2: - movl PER_CPU_VAR(0(%esi)), %eax - movl PER_CPU_VAR(4(%esi)), %edx + movl __percpu (%esi), %eax + movl __percpu 4(%esi), %edx andl $(~X86_EFLAGS_ZF), (%esp) |