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cpu-exec: Unlock tb_lock if we longjmp out of code generation

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If the guest attempts to execute from unreadable memory, this will
cause us to longjmp back to the main loop from inside the
target frontend decoder. For linux-user mode, this means we will
still hold the tb_ctx.tb_lock, and will deadlock when we try to
start executing code again. Unlock the lock in the return-from-longjmp
code path to avoid this.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Andrei Warkentin <andrey.warkentin@gmail.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Peter Maydell 2014-04-04 17:42:56 +01:00
parent cd7ccc8351
commit bae2c27090
1 changed files with 8 additions and 0 deletions
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8
cpu-exec.c
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@ -227,6 +227,8 @@ int cpu_exec(CPUArchState *env)
TranslationBlock *tb;
uint8_t *tc_ptr;
uintptr_t next_tb;
/* This must be volatile so it is not trashed by longjmp() */
volatile bool have_tb_lock = false;
if (cpu->halted) {
if (!cpu_has_work(cpu)) {
@ -600,6 +602,7 @@ int cpu_exec(CPUArchState *env)
cpu_loop_exit(cpu);
}
spin_lock(&tcg_ctx.tb_ctx.tb_lock);
have_tb_lock = true;
tb = tb_find_fast(env);
/* Note: we do it here to avoid a gcc bug on Mac OS X when
doing it in tb_find_slow */
@ -621,6 +624,7 @@ int cpu_exec(CPUArchState *env)
tb_add_jump((TranslationBlock *)(next_tb & ~TB_EXIT_MASK),
next_tb & TB_EXIT_MASK, tb);
}
have_tb_lock = false;
spin_unlock(&tcg_ctx.tb_ctx.tb_lock);
/* cpu_interrupt might be called while translating the
@ -692,6 +696,10 @@ int cpu_exec(CPUArchState *env)
#ifdef TARGET_I386
x86_cpu = X86_CPU(cpu);
#endif
if (have_tb_lock) {
spin_unlock(&tcg_ctx.tb_ctx.tb_lock);
have_tb_lock = false;
}
}
} /* for(;;) */