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From: Peter Maydell <peter.maydell@linaro.org>
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Date: Mon, 13 Nov 2017 14:11:44 +0000
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Subject: [Qemu-devel] [PULL 9/9] accel/tcg/translate-all: expand
cpu_restore_state addr check
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From: Alex Benn=C3=A9e <alex.bennee@linaro.org>
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 Benn=C3=A9e <alex.bennee@linaro.org>
Reported-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20171108153245.20740-2-alex.bennee@linaro.org
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Tested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
include/exec/exec-all.h | 11 ++++++++++
accel/tcg/translate-all.c | 52 ++++++++++++++++++++++++++-----------------=
----
2 files changed, 40 insertions(+), 23 deletions(-)
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 923ece3..0f51c92 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 Tran=
slationBlock *tb,
target_ulong *data);
=20
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);
=20
void QEMU_NORETURN cpu_loop_exit_noexc(CPUState *cpu);
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 34c5e28..e7f0329 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, T=
ranslationBlock *tb,
return 0;
}
=20
-bool cpu_restore_state(CPUState *cpu, uintptr_t retaddr)
+bool cpu_restore_state(CPUState *cpu, uintptr_t host_pc)
{
TranslationBlock *tb;
bool r =3D false;
+ uintptr_t check_offset;
=20
- /* A retaddr of zero is invalid so we really shouldn't have ended
- * up here. The target code has likely forgotten to check retaddr
- * !=3D 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 =3D 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 =3D host_pc - (uintptr_t) tcg_init_ctx.code_gen_buffer;
+
+ if (check_offset < tcg_init_ctx.code_gen_buffer_size) {
+ tb_lock();
+ tb =3D 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 =3D true;
}
- r =3D true;
+ tb_unlock();
}
- tb_unlock();
=20
return r;
}
--=20
2.7.4