linux-user/nios2: Map a real kuser page

The first word of page1 is data, so the whole thing
can't be implemented with emulation of addresses.
Use init_guest_commpage for the allocation.

Hijack trap number 16 to implement cmpxchg.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20211221025012.1057923-5-richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

1 files changed, 27 insertions, 23 deletions

diff --git a/linux-user/nios2/cpu_loop.c b/linux-user/nios2/cpu_loop.c
index 5c3d01d22d..de0fc63e21 100644
--- a/linux-user/nios2/cpu_loop.c
+++ b/linux-user/nios2/cpu_loop.c
@@ -76,6 +76,32 @@ void cpu_loop(CPUNios2State *env)
                 force_sig_fault(TARGET_SIGILL, TARGET_ILL_ILLTRP,
                                 env->regs[R_PC]);
                 break;
+
+            case 16: /* QEMU specific, for __kuser_cmpxchg */
+                {
+                    abi_ptr g = env->regs[4];
+                    uint32_t *h, n, o;
+
+                    if (g & 0x3) {
+                        force_sig_fault(TARGET_SIGBUS, TARGET_BUS_ADRALN, g);
+                        break;
+                    }
+                    ret = page_get_flags(g);
+                    if (!(ret & PAGE_VALID)) {
+                        force_sig_fault(TARGET_SIGSEGV, TARGET_SEGV_MAPERR, g);
+                        break;
+                    }
+                    if (!(ret & PAGE_READ) || !(ret & PAGE_WRITE)) {
+                        force_sig_fault(TARGET_SIGSEGV, TARGET_SEGV_ACCERR, g);
+                        break;
+                    }
+                    h = g2h(cs, g);
+                    o = env->regs[5];
+                    n = env->regs[6];
+                    env->regs[2] = qatomic_cmpxchg(h, o, n) - o;
+                    env->regs[R_PC] += 4;
+                }
+                break;
             }
             break;
 
@@ -86,29 +112,7 @@ void cpu_loop(CPUNios2State *env)
             queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
             break;
         case 0xaa:
-            switch (env->regs[R_PC]) {
-            /*case 0x1000:*/  /* TODO:__kuser_helper_version */
-            case 0x1004:      /* __kuser_cmpxchg */
-                start_exclusive();
-                if (env->regs[4] & 0x3) {
-                    goto kuser_fail;
-                }
-                ret = get_user_u32(env->regs[2], env->regs[4]);
-                if (ret) {
-                    end_exclusive();
-                    goto kuser_fail;
-                }
-                env->regs[2] -= env->regs[5];
-                if (env->regs[2] == 0) {
-                    put_user_u32(env->regs[6], env->regs[4]);
-                }
-                end_exclusive();
-                env->regs[R_PC] = env->regs[R_RA];
-                break;
-            /*case 0x1040:*/  /* TODO:__kuser_sigtramp */
-            default:
-                ;
-kuser_fail:
+            {
                 info.si_signo = TARGET_SIGSEGV;
                 info.si_errno = 0;
                 /* TODO: check env->error_code */