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[Qemu-devel] [RFC v1 02/12] tcg/i386: Make direct jump patching thread-s
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [RFC v1 02/12] tcg/i386: Make direct jump patching thread-safe |
Date: |
Fri, 15 Apr 2016 15:23:41 +0100 |
From: Sergey Fedorov <address@hidden>
Ensure direct jump patching in i386 is atomic by:
* naturally aligning a location of direct jump address;
* using atomic_read()/atomic_set() for code patching.
Signed-off-by: Sergey Fedorov <address@hidden>
Signed-off-by: Sergey Fedorov <address@hidden>
---
include/exec/exec-all.h | 2 +-
tcg/i386/tcg-target.inc.c | 17 +++++++++++++++++
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index cde4b7a..9144ee0 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -324,7 +324,7 @@ void ppc_tb_set_jmp_target(uintptr_t jmp_addr, uintptr_t
addr);
static inline void tb_set_jmp_target1(uintptr_t jmp_addr, uintptr_t addr)
{
/* patch the branch destination */
- stl_le_p((void*)jmp_addr, addr - (jmp_addr + 4));
+ atomic_set((int32_t *)jmp_addr, addr - (jmp_addr + 4));
/* no need to flush icache explicitly */
}
#elif defined(__s390x__)
diff --git a/tcg/i386/tcg-target.inc.c b/tcg/i386/tcg-target.inc.c
index 2f98cae..8fd37f4 100644
--- a/tcg/i386/tcg-target.inc.c
+++ b/tcg/i386/tcg-target.inc.c
@@ -1123,6 +1123,19 @@ static void tcg_out_jmp(TCGContext *s, tcg_insn_unit
*dest)
tcg_out_branch(s, 0, dest);
}
+static void tcg_out_nopn(TCGContext *s, int n)
+{
+ static const uint8_t nop1[] = { 0x90 };
+ static const uint8_t nop2[] = { 0x66, 0x90 };
+ static const uint8_t nop3[] = { 0x8d, 0x76, 0x00 };
+ static const uint8_t *const nopn[] = { nop1, nop2, nop3 };
+ int i;
+ assert(n <= ARRAY_SIZE(nopn));
+ for (i = 0; i < n; ++i) {
+ tcg_out8(s, nopn[n - 1][i]);
+ }
+}
+
#if defined(CONFIG_SOFTMMU)
/* helper signature: helper_ret_ld_mmu(CPUState *env, target_ulong addr,
* int mmu_idx, uintptr_t ra)
@@ -1777,6 +1790,10 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode
opc,
case INDEX_op_goto_tb:
if (s->tb_jmp_insn_offset) {
/* direct jump method */
+ /* align jump displacement for atomic pathing */
+ if (((uintptr_t)s->code_ptr & 3) != 3) {
+ tcg_out_nopn(s, 3 - ((uintptr_t)s->code_ptr & 3));
+ }
tcg_out8(s, OPC_JMP_long); /* jmp im */
s->tb_jmp_insn_offset[args[0]] = tcg_current_code_size(s);
tcg_out32(s, 0);
--
2.7.4
- [Qemu-devel] [RFC v1 00/12] Enable MTTCG for 32 bit arm on x86, Alex Bennée, 2016/04/15
- [Qemu-devel] [RFC v1 02/12] tcg/i386: Make direct jump patching thread-safe,
Alex Bennée <=
- [Qemu-devel] [RFC v1 01/12] include: move CPU-related definitions out of qemu-common.h, Alex Bennée, 2016/04/15
- [Qemu-devel] [RFC v1 00/12] Enable MTTCG for 32 bit arm on x86, Alex Bennée, 2016/04/15
- [Qemu-devel] [RFC v1 03/12] qemu-thread: add simple test-and-set spinlock, Alex Bennée, 2016/04/15
- [Qemu-devel] [RFC v1 04/12] atomic: introduce atomic_dec_fetch., Alex Bennée, 2016/04/15
- [Qemu-devel] [RFC v1 05/12] atomic: introduce cmpxchg_bool, Alex Bennée, 2016/04/15
- [Qemu-devel] [RFC v1 07/12] cpus: introduce async_safe_run_on_cpu., Alex Bennée, 2016/04/15
- [Qemu-devel] [RFC v1 11/12] arm: atomically check the exclusive value in a STREX, Alex Bennée, 2016/04/15
- [Qemu-devel] [RFC v1 10/12] arm: use tlb_flush_page_all for tlbimva[a], Alex Bennée, 2016/04/15