diff options
| author | Alex Bennée <alex.bennee@linaro.org> | 2017-03-20 11:31:44 +0000 |
|---|---|---|
| committer | Alex Bennée <alex.bennee@linaro.org> | 2017-03-28 10:50:35 +0100 |
| commit | 02bed6bd5f45819f1557a4b04db300a72383ecdb (patch) | |
| tree | 878016bb7d1d5aed3dba30f136eeca3cca8ccdd4 /user-exec.c | |
| parent | ea2afcf5b6727a577cf561fd8fe0d8c397ecc927 (diff) | |
user-exec: handle synchronous signals from QEMU gracefully
When "tcg: enable thread-per-vCPU" (commit 3725794) was merged the
lifetime of current_cpu was changed. Previously a broken linux-user
call might abort() which can eventually escalate into a SIGSEGV which
would then crash qemu as it attempted to deref a NULL current_cpu.
After commit 3725794 it would attempt to fixup state and re-start the
run-loop and much hilarity (i.e. a looping lockup) would ensue from
jumping into a stale jmp_env.
As we can actually tell if we are in the run-loop from looking at the
cpu->running flag we should catch this badness first and abort()
cleanly rather than try to soldier on. There is a theoretical race
between the flag being set and sigsetjmp refreshing the jump buffer
but we can try really hard to not introduce crashes into that code.
[LV: setgroups03 fails on powerpc LTP]
Reported-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'user-exec.c')
| -rw-r--r-- | user-exec.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/user-exec.c b/user-exec.c index 6db075884d..a8f95fa1e1 100644 --- a/user-exec.c +++ b/user-exec.c @@ -57,10 +57,23 @@ static void cpu_exit_tb_from_sighandler(CPUState *cpu, sigset_t *old_set) static inline int handle_cpu_signal(uintptr_t pc, unsigned long address, int is_write, sigset_t *old_set) { - CPUState *cpu; + CPUState *cpu = current_cpu; CPUClass *cc; int ret; + /* For synchronous signals we expect to be coming from the vCPU + * thread (so current_cpu should be valid) and either from running + * code or during translation which can fault as we cross pages. + * + * If neither is true then something has gone wrong and we should + * abort rather than try and restart the vCPU execution. + */ + if (!cpu || !cpu->running) { + printf("qemu:%s received signal outside vCPU context @ pc=0x%" + PRIxPTR "\n", __func__, pc); + abort(); + } + #if defined(DEBUG_SIGNAL) printf("qemu: SIGSEGV pc=0x%08lx address=%08lx w=%d oldset=0x%08lx\n", pc, address, is_write, *(unsigned long *)old_set); @@ -83,7 +96,7 @@ static inline int handle_cpu_signal(uintptr_t pc, unsigned long address, * currently executing TB was modified and must be exited * immediately. */ - cpu_exit_tb_from_sighandler(current_cpu, old_set); + cpu_exit_tb_from_sighandler(cpu, old_set); g_assert_not_reached(); default: g_assert_not_reached(); @@ -94,7 +107,6 @@ static inline int handle_cpu_signal(uintptr_t pc, unsigned long address, are still valid segv ones */ address = h2g_nocheck(address); - cpu = current_cpu; cc = CPU_GET_CLASS(cpu); /* see if it is an MMU fault */ g_assert(cc->handle_mmu_fault); |