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59bec00ace
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>
55 lines
1,009 B
ArmAsm
55 lines
1,009 B
ArmAsm
/* SPDX-License-Identifier: GPL-2.0-only */
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#include <linux/linkage.h>
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#include <asm/percpu.h>
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#include <asm/processor-flags.h>
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.text
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/*
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* Emulate 'cmpxchg16b %gs:(%rsi)'
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*
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* Inputs:
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* %rsi : memory location to compare
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* %rax : low 64 bits of old value
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* %rdx : high 64 bits of old value
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* %rbx : low 64 bits of new value
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* %rcx : high 64 bits of new value
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*
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* Notably this is not LOCK prefixed and is not safe against NMIs
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*/
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SYM_FUNC_START(this_cpu_cmpxchg16b_emu)
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pushfq
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cli
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/* if (*ptr == old) */
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cmpq __percpu (%rsi), %rax
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jne .Lnot_same
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cmpq __percpu 8(%rsi), %rdx
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jne .Lnot_same
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/* *ptr = new */
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movq %rbx, __percpu (%rsi)
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movq %rcx, __percpu 8(%rsi)
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/* set ZF in EFLAGS to indicate success */
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orl $X86_EFLAGS_ZF, (%rsp)
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popfq
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RET
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.Lnot_same:
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/* *ptr != old */
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/* old = *ptr */
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movq __percpu (%rsi), %rax
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movq __percpu 8(%rsi), %rdx
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/* clear ZF in EFLAGS to indicate failure */
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andl $(~X86_EFLAGS_ZF), (%rsp)
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popfq
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RET
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SYM_FUNC_END(this_cpu_cmpxchg16b_emu)
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