[Qemu-devel] [PATCH] arm: fix TB alignment check

[Pavel Dovgalyuk]

Sometimes page faults happen during the translation of the target instructions.
To avoid the faults in the middle of the TB we have to stop translation at
the end of the page. Current implementation of ARM translation assumes that
instructions are aligned to their own size (4 or 2 bytes). But in thumb2 mode
4-byte instruction can be aligned to 2 bytes. In some cases such an alignment
leads to page fault.
This patch adds check that allows translation of such instructions only in
the beginning of the TB.

Signed-off-by: Pavel Dovgalyuk <address@hidden>
---
 target-arm/translate.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/target-arm/translate.c b/target-arm/translate.c
index 2c0b1de..bc3a16b 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -11124,7 +11124,8 @@ static inline void 
gen_intermediate_code_internal(ARMCPU *cpu,
              !cs->singlestep_enabled &&
              !singlestep &&
              !dc->ss_active &&
-             dc->pc < next_page_start &&
+             /* +3 is for unaligned Thumb2 instructions */
+             dc->pc + 3 < next_page_start &&
              num_insns < max_insns);
 
     if (tb->cflags & CF_LAST_IO) {