[PATCH v3 18/21] linux-user/aarch64: Signal SEGV_MTEAERR for async tag check error

From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org, qemu-arm@nongnu.org
Subject: [PATCH v3 18/21] linux-user/aarch64: Signal SEGV_MTEAERR for async tag check error
Date: Fri, 15 Jan 2021 12:46:42 -1000	[thread overview]
Message-ID: <20210115224645.1196742-19-richard.henderson@linaro.org> (raw)
In-Reply-To: <20210115224645.1196742-1-richard.henderson@linaro.org>

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/aarch64/target_signal.h |  1 +
 linux-user/aarch64/cpu_loop.c      | 34 +++++++++++++++++++++---------
 target/arm/mte_helper.c            | 10 +++++++++
 3 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/linux-user/aarch64/target_signal.h b/linux-user/aarch64/target_signal.h
index 777fb667fe..18013e1b23 100644
--- a/linux-user/aarch64/target_signal.h
+++ b/linux-user/aarch64/target_signal.h
@@ -21,6 +21,7 @@ typedef struct target_sigaltstack {
 
 #include "../generic/signal.h"
 
+#define TARGET_SEGV_MTEAERR  8  /* Asynchronous ARM MTE error */
 #define TARGET_SEGV_MTESERR  9  /* Synchronous ARM MTE exception */
 
 #define TARGET_ARCH_HAS_SETUP_FRAME
diff --git a/linux-user/aarch64/cpu_loop.c b/linux-user/aarch64/cpu_loop.c
index 6867f0db2b..6160a401bd 100644
--- a/linux-user/aarch64/cpu_loop.c
+++ b/linux-user/aarch64/cpu_loop.c
@@ -72,6 +72,21 @@
         put_user_u16(__x, (gaddr));                     \
     })
 
+static bool check_mte_async_fault(CPUARMState *env, target_siginfo_t *info)
+{
+    if (likely(env->cp15.tfsr_el[0] == 0)) {
+        return false;
+    }
+
+    env->cp15.tfsr_el[0] = 0;
+    info->si_signo = TARGET_SIGSEGV;
+    info->si_errno = 0;
+    info->_sifields._sigfault._addr = 0;
+    info->si_code = TARGET_SEGV_MTEAERR;
+    queue_signal(env, info->si_signo, QEMU_SI_FAULT, info);
+    return true;
+}
+
 /* AArch64 main loop */
 void cpu_loop(CPUARMState *env)
 {
@@ -88,15 +103,13 @@ void cpu_loop(CPUARMState *env)
 
         switch (trapnr) {
         case EXCP_SWI:
-            ret = do_syscall(env,
-                             env->xregs[8],
-                             env->xregs[0],
-                             env->xregs[1],
-                             env->xregs[2],
-                             env->xregs[3],
-                             env->xregs[4],
-                             env->xregs[5],
-                             0, 0);
+            if (check_mte_async_fault(env, &info)) {
+                ret = -TARGET_ERESTARTSYS;
+            } else {
+                ret = do_syscall(env, env->xregs[8], env->xregs[0],
+                                 env->xregs[1], env->xregs[2], env->xregs[3],
+                                 env->xregs[4], env->xregs[5], 0, 0);
+            }
             if (ret == -TARGET_ERESTARTSYS) {
                 env->pc -= 4;
             } else if (ret != -TARGET_QEMU_ESIGRETURN) {
@@ -104,7 +117,8 @@ void cpu_loop(CPUARMState *env)
             }
             break;
         case EXCP_INTERRUPT:
-            /* just indicate that signals should be handled asap */
+            /* Just indicate that signals should be handled asap. */
+            check_mte_async_fault(env, &info);
             break;
         case EXCP_UDEF:
             info.si_signo = TARGET_SIGILL;
diff --git a/target/arm/mte_helper.c b/target/arm/mte_helper.c
index 153bd1e9df..d55f8d1e1e 100644
--- a/target/arm/mte_helper.c
+++ b/target/arm/mte_helper.c
@@ -565,6 +565,16 @@ static void mte_check_fail(CPUARMState *env, uint32_t desc,
             select = 0;
         }
         env->cp15.tfsr_el[el] |= 1 << select;
+#ifdef CONFIG_USER_ONLY
+        /*
+         * Stand in for a timer irq, setting _TIF_MTE_ASYNC_FAULT,
+         * which then sends a SIGSEGV when the thread is next scheduled.
+         * This cpu will return to the main loop at the end of the TB,
+         * which is rather sooner than "normal".  But the alternative
+         * is waiting until the next syscall.
+         */
+        qemu_cpu_kick(env_cpu(env));
+#endif
         break;
 
     default:
-- 
2.25.1


