[Qemu-devel] [PATCH 01/26] tcg-aarch64: Properly detect SIGSEGV writes

[Richard Henderson <rth@twiddle.net>]

Since the kernel doesn't pass any info on the reason for the fault,
disassemble the instruction to detect a store.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 user-exec.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/user-exec.c b/user-exec.c
index bc58056..4c0cd46 100644
--- a/user-exec.c
+++ b/user-exec.c
@@ -465,16 +465,33 @@ int cpu_signal_handler(int host_signum, void *pinfo,
 
 #elif defined(__aarch64__)
 
-int cpu_signal_handler(int host_signum, void *pinfo,
-                       void *puc)
+int cpu_signal_handler(int host_signum, void *pinfo, void *puc)
 {
     siginfo_t *info = pinfo;
     struct ucontext *uc = puc;
-    uint64_t pc;
-    int is_write = 0; /* XXX how to determine? */
+    uintptr_t pc = uc->uc_mcontext.pc;
+    uint32_t insn = *(uint32_t *)pc;
+    bool is_write;
 
-    pc = uc->uc_mcontext.pc;
-    return handle_cpu_signal(pc, (uint64_t)info->si_addr,
+    /* XXX: need kernel patch to get write flag faster.  */
+    /* XXX: several of these could be combined.  */
+    is_write = (   (insn & 0xbfff0000) == 0x0c000000   /* C3.3.1 */
+                || (insn & 0xbfe00000) == 0x0c800000   /* C3.3.2 */
+                || (insn & 0xbfff0000) == 0x0d000000   /* C3.3.3 */
+                || (insn & 0xbfe00000) == 0x0d800000   /* C3.3.4 */
+                || (insn & 0x3f400000) == 0x08000000   /* C3.3.6 */
+                || (insn & 0x3bc00000) == 0x28400000   /* C3.3.7 */
+                || (insn & 0x3be00c00) == 0x38000400   /* C3.3.8 */
+                || (insn & 0x3be00c00) == 0x38000c00   /* C3.3.9 */
+                || (insn & 0x3be00c00) == 0x38200800   /* C3.3.10 */
+                || (insn & 0x3be00c00) == 0x38000800   /* C3.3.11 */
+                || (insn & 0x3be00c00) == 0x38000000   /* C3.3.12 */
+                || (insn & 0x3bc00000) == 0x39000000   /* C3.3.13 */
+                || (insn & 0x3bc00000) == 0x29000000   /* C3.3.14 */
+                || (insn & 0x3bc00000) == 0x28800000   /* C3.3.15 */
+                || (insn & 0x3bc00000) == 0x29800000); /* C3.3.16 */
+
+    return handle_cpu_signal(pc, (uintptr_t)info->si_addr,
                              is_write, &uc->uc_sigmask, puc);
 }
 
-- 
1.8.5.3