tcg/aarch64: Make direct jump patching thread-safe

Ensure direct jump patching in AArch64 is atomic by using
atomic_read()/atomic_set() for code patching.

Signed-off-by: Sergey Fedorov <[email protected]>
Signed-off-by: Sergey Fedorov <[email protected]>
Message-Id: <1461341333[email protected]>
Signed-off-by: Richard Henderson <[email protected]>

diff --git a/tcg/aarch64/tcg-target.inc.c b/tcg/aarch64/tcg-target.inc.c
index a8fb4420defe3d3f5d6a9da14ececd19185d6d73..88183c830fb0c26ae6dd726036254cf10d257ff5 100644 (file)
--- a/tcg/aarch64/tcg-target.inc.c
+++ b/tcg/aarch64/tcg-target.inc.c
@@ -73,6 +73,18 @@ static inline void reloc_pc26(tcg_insn_unit *code_ptr, tcg_insn_unit *target)
     *code_ptr = deposit32(*code_ptr, 0, 26, offset);
 }
 
+static inline void reloc_pc26_atomic(tcg_insn_unit *code_ptr,
+                                     tcg_insn_unit *target)
+{
+    ptrdiff_t offset = target - code_ptr;
+    tcg_insn_unit insn;
+    tcg_debug_assert(offset == sextract64(offset, 0, 26));
+    /* read instruction, mask away previous PC_REL26 parameter contents,
+       set the proper offset, then write back the instruction. */
+    insn = atomic_read(code_ptr);
+    atomic_set(code_ptr, deposit32(insn, 0, 26, offset));
+}
+
 static inline void reloc_pc19(tcg_insn_unit *code_ptr, tcg_insn_unit *target)
 {
     ptrdiff_t offset = target - code_ptr;
@@ -835,7 +847,7 @@ void aarch64_tb_set_jmp_target(uintptr_t jmp_addr, uintptr_t addr)
     tcg_insn_unit *code_ptr = (tcg_insn_unit *)jmp_addr;
     tcg_insn_unit *target = (tcg_insn_unit *)addr;
 
-    reloc_pc26(code_ptr, target);
+    reloc_pc26_atomic(code_ptr, target);
     flush_icache_range(jmp_addr, jmp_addr + 4);
 }