linux-user/mips: implement sysmips(MIPS_ATOMIC_SET)

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 <richard.henderson@linaro.org>
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20260520172313.23777-3-philmd@linaro.org>

diff --git a/linux-user/mips/target_syscall.h b/linux-user/mips/target_syscall.h
index 3f36c1695a59d6e72c49f917c03fcc3fd808a95b..9206694f4fb0869855b6371886c49d9d29ff7951 100644 (file)
--- 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 20ea7c6ab9bc88f09ee75ffe2aea6660ce3a9e73..e07687f8ac94e7d76f2ee6736b330c30d5e71d67 100644 (file)
--- 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 5a8e00337a04a274dd6563acc14200619ce2a5cb..3df42aa159d6a36d34b2adb89df0152b8bf08192 100644 (file)
--- 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: