[PATCH for-9.0] linux-user: Preserve unswapped siginfo_t for strace

[PATCH for-9.0] linux-user: Preserve unswapped siginfo_t for strace

[Richard Henderson]

Passing the tswapped structure to strace means that
our internal si_type is also gone, which then aborts
in print_siginfo.

Fixes: 4d6d8a05a0a ("linux-user: Move tswap_siginfo out of target code")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/signal.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/linux-user/signal.c b/linux-user/signal.c
index a93148a4cb..05dc4afb52 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -1173,6 +1173,7 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig,
     CPUState *cpu = env_cpu(cpu_env);
     abi_ulong handler;
     sigset_t set;
+    target_siginfo_t unswapped;
     target_sigset_t target_old_set;
     struct target_sigaction *sa;
     TaskState *ts = get_task_state(cpu);
@@ -1182,9 +1183,14 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig,
     k->pending = 0;
 
     /*
-     * Writes out siginfo values byteswapped, accordingly to the target. It also
-     * cleans the si_type from si_code making it correct for the target.
+     * Writes out siginfo values byteswapped, accordingly to the target.
+     * It also cleans the si_type from si_code making it correct for
+     * the target.  We must hold on to the original unswapped copy for
+     * strace below, because si_type is still required there.
      */
+    if (unlikely(qemu_loglevel_mask(LOG_STRACE))) {
+        unswapped = k->info;
+    }
     tswap_siginfo(&k->info, &k->info);
 
     sig = gdb_handlesig(cpu, sig, NULL, &k->info, sizeof(k->info));
@@ -1197,7 +1203,7 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig,
     }
 
     if (unlikely(qemu_loglevel_mask(LOG_STRACE))) {
-        print_taken_signal(sig, &k->info);
+        print_taken_signal(sig, &unswapped);
     }
 
     if (handler == TARGET_SIG_DFL) {
-- 
2.34.1

Re: [PATCH for-9.0] linux-user: Preserve unswapped siginfo_t for strace

[Philippe Mathieu-Daudé]

On 9/4/24 02:34, Richard Henderson wrote:
> Passing the tswapped structure to strace means that
> our internal si_type is also gone, which then aborts
> in print_siginfo.
> 
> Fixes: 4d6d8a05a0a ("linux-user: Move tswap_siginfo out of target code")
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   linux-user/signal.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>