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linux-user: Remap guest SIGABRT

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Distinguish host SIGABRT from guest SIGABRT by mapping
the guest signal onto one of the host RT signals.

This prevents a cycle by which a host assertion failure
is caught and handled by host_signal_handler, queued for
the guest, and then we attempt to continue past the
host abort.  What happens next depends on the host libc,
but is neither good nor helpful.

Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2023-09-30 12:05:11 -07:00
parent 4a6ebc19a7
commit 38ee0a7dfb
1 changed files with 35 additions and 7 deletions
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42
linux-user/signal.c
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@ -522,8 +522,21 @@ static void signal_table_init(void)
* multiplexed over a single host signal.
* Attempts for configure "missing" signals via sigaction will be
* silently ignored.
*
* Remap the target SIGABRT, so that we can distinguish host abort
* from guest abort. When the guest registers a signal handler or
* calls raise(SIGABRT), the host will raise SIG_RTn. If the guest
* arrives at dump_core_and_abort(), we will map back to host SIGABRT
* so that the parent (native or emulated) sees the correct signal.
* Finally, also map host to guest SIGABRT so that the emulated
* parent sees the correct mapping from wait status.
*/
for (hsig = SIGRTMIN; hsig <= SIGRTMAX; hsig++) {
hsig = SIGRTMIN;
host_to_target_signal_table[SIGABRT] = 0;
host_to_target_signal_table[hsig++] = TARGET_SIGABRT;
for (; hsig <= SIGRTMAX; hsig++) {
tsig = hsig - SIGRTMIN + TARGET_SIGRTMIN;
if (tsig <= TARGET_NSIG) {
host_to_target_signal_table[hsig] = tsig;
@ -539,6 +552,8 @@ static void signal_table_init(void)
}
}
host_to_target_signal_table[SIGABRT] = TARGET_SIGABRT;
/* Map everything else out-of-bounds. */
for (hsig = 1; hsig < _NSIG; hsig++) {
if (host_to_target_signal_table[hsig] == 0) {
@ -582,13 +597,21 @@ void signal_init(void)
int hsig = target_to_host_signal(tsig);
abi_ptr thand = TARGET_SIG_IGN;
if (hsig < _NSIG) {
struct sigaction *iact = core_dump_signal(tsig) ? &act : NULL;
if (hsig >= _NSIG) {
continue;
}
/* As we force remap SIGABRT, cannot probe and install in one step. */
if (tsig == TARGET_SIGABRT) {
sigaction(SIGABRT, NULL, &oact);
sigaction(hsig, &act, NULL);
} else {
struct sigaction *iact = core_dump_signal(tsig) ? &act : NULL;
sigaction(hsig, iact, &oact);
if (oact.sa_sigaction != (void *)SIG_IGN) {
thand = TARGET_SIG_DFL;
}
}
if (oact.sa_sigaction != (void *)SIG_IGN) {
thand = TARGET_SIG_DFL;
}
sigact_table[tsig - 1]._sa_handler = thand;
}
@ -711,7 +734,12 @@ void dump_core_and_abort(CPUArchState *env, int target_sig)
TaskState *ts = (TaskState *)cpu->opaque;
int host_sig, core_dumped = 0;
host_sig = target_to_host_signal(target_sig);
/* On exit, undo the remapping of SIGABRT. */
if (target_sig == TARGET_SIGABRT) {
host_sig = SIGABRT;
} else {
host_sig = target_to_host_signal(target_sig);
}
trace_user_dump_core_and_abort(env, target_sig, host_sig);
gdb_signalled(env, target_sig);