Implement the MIPS_ATOMIC_SET sysmips command as an aligned 32-bit atomic exchange in target memory.
MIPS reports syscall errors through a separate register, so successful old values can overlap the errno range. Write the return value and error flag directly and return -QEMU_ESIGRETURN so the common syscall path leaves the registers unchanged. Reviewed-by: Richard Henderson <[email protected]> Signed-off-by: James Hilliard <[email protected]> --- Changes v2 -> v3: - Split MIPS_ATOMIC_SET out of the combined sysmips/MIPS_FIXADE patch. (suggested by Richard Henderson) - Always use the explicit MIPS return-register path for successful atomic_set results. (suggested by Richard Henderson) --- linux-user/mips/target_syscall.h | 1 + linux-user/mips64/target_syscall.h | 1 + linux-user/syscall.c | 31 +++++++++++++++++++++++++++++++ 3 files changed, 33 insertions(+) diff --git a/linux-user/mips/target_syscall.h b/linux-user/mips/target_syscall.h index 3f36c1695a..9206694f4f 100644 --- a/linux-user/mips/target_syscall.h +++ b/linux-user/mips/target_syscall.h @@ -11,6 +11,7 @@ #define TARGET_FORCE_SHMLBA #define TARGET_SYSMIPS_FLUSH_CACHE 3 +#define TARGET_SYSMIPS_ATOMIC_SET 2001 static inline abi_ulong target_shmlba(CPUMIPSState *env) { diff --git a/linux-user/mips64/target_syscall.h b/linux-user/mips64/target_syscall.h index 20ea7c6ab9..e07687f8ac 100644 --- a/linux-user/mips64/target_syscall.h +++ b/linux-user/mips64/target_syscall.h @@ -11,6 +11,7 @@ #define TARGET_FORCE_SHMLBA #define TARGET_SYSMIPS_FLUSH_CACHE 3 +#define TARGET_SYSMIPS_ATOMIC_SET 2001 static inline abi_ulong target_shmlba(CPUMIPSState *env) { diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 73f09bb775..3786a34041 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -6631,10 +6631,41 @@ static abi_long do_prctl_syscall_user_dispatch(CPUArchState *env, } #ifdef TARGET_NR_sysmips +static abi_long do_sysmips_atomic_set(CPUArchState *env, abi_ulong addr, + abi_long value) +{ + uint32_t *ptr; + abi_long old; + + if (addr & 3) { + return -TARGET_EINVAL; + } + + ptr = lock_user(VERIFY_WRITE, addr, sizeof(*ptr), true); + if (!ptr) { + return -TARGET_EINVAL; + } + + old = tswap32(qatomic_xchg(ptr, tswap32((uint32_t)value))); + unlock_user(ptr, addr, sizeof(*ptr)); + + /* + * MIPS uses a separate error flag, but the common linux-user syscall + * path infers that flag from the return value. Successful atomic_set + * results can overlap the target errno range, so write the result + * registers here and ask the CPU loop to leave them alone. + */ + env->active_tc.gpr[2] = old; + env->active_tc.gpr[7] = 0; + return -QEMU_ESIGRETURN; +} + static abi_long do_sysmips(CPUArchState *env, abi_long cmd, abi_long arg1, abi_long arg2) { switch (cmd) { + case TARGET_SYSMIPS_ATOMIC_SET: + return do_sysmips_atomic_set(env, arg1, arg2); case TARGET_SYSMIPS_FLUSH_CACHE: return 0; default: -- 2.54.0
