Le 08/11/2017 à 16:32, Alex Bennée a écrit :
> We are still seeing signals during translation time when we walk over
> a page protection boundary. This expands the check to ensure the host
> PC is inside the code generation buffer. The original suggestion was
> to check versus tcg_ctx.code_gen_ptr but as we now segment the
> translation buffer we have to settle for just a general check for
> being inside.
>
> I've also fixed up the declaration to make it clear it can deal with
> invalid addresses. A later patch will fix up the call sites.
>
> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
> Reported-by: Peter Maydell <peter.mayd...@linaro.org>
> Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
> Cc: Richard Henderson <r...@twiddle.net>
>
> ---
> v2:
> - add doc comment to exec-all.h
> - retaddr->host_pc
> - re-word comments on host_pc
> - simplify logic as per rth suggestion
> ---
> accel/tcg/translate-all.c | 52
> ++++++++++++++++++++++++++---------------------
> include/exec/exec-all.h | 11 ++++++++++
> 2 files changed, 40 insertions(+), 23 deletions(-)
>
> diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
> index 34c5e28d07..e7f0329a52 100644
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -352,36 +352,42 @@ static int cpu_restore_state_from_tb(CPUState *cpu,
> TranslationBlock *tb,
> return 0;
> }
>
> -bool cpu_restore_state(CPUState *cpu, uintptr_t retaddr)
> +bool cpu_restore_state(CPUState *cpu, uintptr_t host_pc)
> {
> TranslationBlock *tb;
> bool r = false;
> + uintptr_t check_offset;
>
> - /* A retaddr of zero is invalid so we really shouldn't have ended
> - * up here. The target code has likely forgotten to check retaddr
> - * != 0 before attempting to restore state. We return early to
> - * avoid blowing up on a recursive tb_lock(). The target must have
> - * previously survived a failed cpu_restore_state because
> - * tb_find_pc(0) would have failed anyway. It still should be
> - * fixed though.
> + /* The host_pc has to be in the region of current code buffer. If
> + * it is not we will not be able to resolve it here. The two cases
> + * where host_pc will not be correct are:
> + *
> + * - fault during translation (instruction fetch)
> + * - fault from helper (not using GETPC() macro)
> + *
> + * Either way we need return early to avoid blowing up on a
> + * recursive tb_lock() as we can't resolve it here.
> + *
> + * We are using unsigned arithmetic so if host_pc <
> + * tcg_init_ctx.code_gen_buffer check_offset will wrap to way
> + * above the code_gen_buffer_size
> */
> -
> - if (!retaddr) {
> - return r;
> - }
> -
> - tb_lock();
> - tb = tb_find_pc(retaddr);
> - if (tb) {
> - cpu_restore_state_from_tb(cpu, tb, retaddr);
> - if (tb->cflags & CF_NOCACHE) {
> - /* one-shot translation, invalidate it immediately */
> - tb_phys_invalidate(tb, -1);
> - tb_remove(tb);
> + check_offset = host_pc - (uintptr_t) tcg_init_ctx.code_gen_buffer;
> +
> + if (check_offset < tcg_init_ctx.code_gen_buffer_size) {
> + tb_lock();
> + tb = tb_find_pc(host_pc);
> + if (tb) {
> + cpu_restore_state_from_tb(cpu, tb, host_pc);
> + if (tb->cflags & CF_NOCACHE) {
> + /* one-shot translation, invalidate it immediately */
> + tb_phys_invalidate(tb, -1);
> + tb_remove(tb);
> + }
> + r = true;
> }
> - r = true;
> + tb_unlock();
> }
> - tb_unlock();
>
> return r;
> }
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index 923ece3e9b..0f51c92adb 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -45,6 +45,17 @@ void restore_state_to_opc(CPUArchState *env, struct
> TranslationBlock *tb,
> target_ulong *data);
>
> void cpu_gen_init(void);
> +
> +/**
> + * cpu_restore_state:
> + * @cpu: the vCPU state is to be restore to
> + * @searched_pc: the host PC the fault occurred at
> + * @return: true if state was restored, false otherwise
> + *
> + * Attempt to restore the state for a fault occurring in translated
> + * code. If the searched_pc is not in translated code no state is
> + * restored and the function returns false.
> + */
> bool cpu_restore_state(CPUState *cpu, uintptr_t searched_pc);
>
> void QEMU_NORETURN cpu_loop_exit_noexc(CPUState *cpu);
>
Reviewed-by: Laurent Vivier <laur...@vivier.eu>
