72 lines
2.3 KiB
C
72 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <vdso/futex.h>
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/*
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* Assembly template for the try unlock functions. The basic functionality is:
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*
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* mov esi, %eax Move the TID into EAX
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* xor %ecx, %ecx Clear ECX
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* lock_cmpxchgl %ecx, (%rdi) Attempt the TID -> 0 transition
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* .Lcs_start: Start of the critical section
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* jnz .Lcs_end If cmpxchl failed jump to the end
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* .Lcs_success: Start of the success section
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* movq %rcx, (%rdx) Set the pending op pointer to 0
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* .Lcs_end: End of the critical section
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*
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* .Lcs_start and .Lcs_end establish the critical section range. .Lcs_success is
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* technically not required, but there for illustration, debugging and testing.
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*
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* When CONFIG_COMPAT is enabled then the 64-bit VDSO provides two functions.
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* One for the regular 64-bit sized pending operation pointer and one for a
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* 32-bit sized pointer to support gaming emulators.
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*
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* The 32-bit VDSO provides only the one for 32-bit sized pointers.
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*/
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#define __stringify_1(x...) #x
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#define __stringify(x...) __stringify_1(x)
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#define LABEL(prefix, which) __stringify(prefix##_try_unlock_cs_##which:)
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#define JNZ_END(prefix) "jnz " __stringify(prefix) "_try_unlock_cs_end\n"
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#define CLEAR_POPQ "movq %[zero], %a[pop]\n"
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#define CLEAR_POPL "movl %k[zero], %a[pop]\n"
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#define futex_robust_try_unlock(prefix, clear_pop, __lock, __tid, __pop)\
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({ \
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asm volatile ( \
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" \n" \
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" lock cmpxchgl %k[zero], %a[lock] \n" \
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" \n" \
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LABEL(prefix, start) \
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" \n" \
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JNZ_END(prefix) \
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" \n" \
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LABEL(prefix, success) \
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" \n" \
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clear_pop \
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" \n" \
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LABEL(prefix, end) \
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: [tid] "+&a" (__tid) \
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: [lock] "D" (__lock), \
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[pop] "d" (__pop), \
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[zero] "r" (0UL) \
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: "memory" \
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); \
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__tid; \
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})
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#ifdef __x86_64__
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__u32 __vdso_futex_robust_list64_try_unlock(__u32 *lock, __u32 tid, __u64 *pop)
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{
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return futex_robust_try_unlock(__futex_list64, CLEAR_POPQ, lock, tid, pop);
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}
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#endif /* __x86_64__ */
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#if defined(CONFIG_X86_32) || defined(CONFIG_COMPAT)
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__u32 __vdso_futex_robust_list32_try_unlock(__u32 *lock, __u32 tid, __u32 *pop)
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{
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return futex_robust_try_unlock(__futex_list32, CLEAR_POPL, lock, tid, pop);
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}
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#endif /* CONFIG_X86_32 || CONFIG_COMPAT */
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