// SPDX-License-Identifier: GPL-2.0-only
#include <vdso/futex.h>

/*
 * Assembly template for the try unlock functions. The basic functionality is:
 *
 *              mov             esi, %eax       Move the TID into EAX
 *              xor             %ecx, %ecx      Clear ECX
 *              lock_cmpxchgl   %ecx, (%rdi)    Attempt the TID -> 0 transition
 * .Lcs_start:                                  Start of the critical section
 *              jnz             .Lcs_end        If cmpxchl failed jump to the end
 * .Lcs_success:                                Start of the success section
 *              movq            %rcx, (%rdx)    Set the pending op pointer to 0
 * .Lcs_end:                                    End of the critical section
 *
 * .Lcs_start and .Lcs_end establish the critical section range. .Lcs_success is
 * technically not required, but there for illustration, debugging and testing.
 *
 * When CONFIG_COMPAT is enabled then the 64-bit VDSO provides two functions.
 * One for the regular 64-bit sized pending operation pointer and one for a
 * 32-bit sized pointer to support gaming emulators.
 *
 * The 32-bit VDSO provides only the one for 32-bit sized pointers.
 */
#define __stringify_1(x...)     #x
#define __stringify(x...)       __stringify_1(x)

#define LABEL(prefix, which)    __stringify(prefix##_try_unlock_cs_##which:)

#define JNZ_END(prefix)         "jnz " __stringify(prefix) "_try_unlock_cs_end\n"

#define CLEAR_POPQ              "movq   %[zero],  %a[pop]\n"
#define CLEAR_POPL              "movl   %k[zero], %a[pop]\n"

#define futex_robust_try_unlock(prefix, clear_pop, __lock, __tid, __pop)\
({                                                                      \
        asm volatile (                                                  \
                "                                               \n"     \
                "       lock cmpxchgl   %k[zero], %a[lock]      \n"     \
                "                                               \n"     \
                LABEL(prefix, start)                                    \
                "                                               \n"     \
                JNZ_END(prefix)                                         \
                "                                               \n"     \
                LABEL(prefix, success)                                  \
                "                                               \n"     \
                        clear_pop                                       \
                "                                               \n"     \
                LABEL(prefix, end)                                      \
                : [tid]   "+&a" (__tid)                                 \
                : [lock]  "D"   (__lock),                               \
                  [pop]   "d"   (__pop),                                \
                  [zero]  "r"   (0UL)                                   \
                : "memory"                                              \
        );                                                              \
        __tid;                                                          \
})

#ifdef __x86_64__
__u32 __vdso_futex_robust_list64_try_unlock(__u32 *lock, __u32 tid, __u64 *pop)
{
        return futex_robust_try_unlock(__futex_list64, CLEAR_POPQ, lock, tid, pop);
}
#endif /* __x86_64__ */

#if defined(CONFIG_X86_32) || defined(CONFIG_COMPAT)
__u32 __vdso_futex_robust_list32_try_unlock(__u32 *lock, __u32 tid, __u32 *pop)
{
        return futex_robust_try_unlock(__futex_list32, CLEAR_POPL, lock, tid, pop);
}
#endif /* CONFIG_X86_32 || CONFIG_COMPAT */