From: Sergey Fedorov <serge.f...@gmail.com>
Ensure direct jump patching in s390 is atomic by:
* naturally aligning a location of direct jump address;
* using atomic_read()/atomic_set() for code patching.
Signed-off-by: Sergey Fedorov <serge.f...@gmail.com>
Signed-off-by: Sergey Fedorov <sergey.fedo...@linaro.org>
Message-Id: <1461341333-19646-7-git-send-email-sergey.fedo...@linaro.org>
Signed-off-by: Richard Henderson <r...@twiddle.net>
---
include/exec/exec-all.h | 2 +-
tcg/s390/tcg-target.inc.c | 8 ++++++++
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 0ab7803..6c095e8 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -321,7 +321,7 @@ static inline void tb_set_jmp_target1(uintptr_t jmp_addr,
uintptr_t addr)
{
/* patch the branch destination */
intptr_t disp = addr - (jmp_addr - 2);
- stl_be_p((void*)jmp_addr, disp / 2);
+ atomic_set((int32_t *)jmp_addr, disp / 2);
/* no need to flush icache explicitly */
}
#elif defined(__aarch64__)
diff --git a/tcg/s390/tcg-target.inc.c b/tcg/s390/tcg-target.inc.c
index 5805532..8e8064c 100644
--- a/tcg/s390/tcg-target.inc.c
+++ b/tcg/s390/tcg-target.inc.c
@@ -219,6 +219,8 @@ typedef enum S390Opcode {
RX_ST = 0x50,
RX_STC = 0x42,
RX_STH = 0x40,
+
+ NOP = 0x0707,
} S390Opcode;
#ifdef CONFIG_DEBUG_TCG
@@ -1716,6 +1718,12 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode
opc,
case INDEX_op_goto_tb:
if (s->tb_jmp_offset) {
+ /* branch displacement must be aligned for atomic patching;
+ * see if we need to add extra nop before branch
+ */
+ if (!QEMU_PTR_IS_ALIGNED(s->code_ptr + 1, 4)) {
+ tcg_out16(s, NOP);
+ }
tcg_out16(s, RIL_BRCL | (S390_CC_ALWAYS << 4));
s->tb_jmp_offset[args[0]] = tcg_current_code_size(s);
s->code_ptr += 2;
--
2.5.5
