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tcg/s390: Make direct jump patching thread-safe

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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.

Backports commit ed3d51ecd7fe248d3959e469d53890ac9ffe0cd2 from qemu
This commit is contained in:
Sergey Fedorov 2018-02-23 20:38:29 -05:00 committed by Lioncash
parent 5eb2d6618f
commit 57359fbe6c
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GPG key ID: 4E3C3CC1031BA9C7
2 changed files with 9 additions and 1 deletions
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2
qemu/include/exec/exec-all.h
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@ -315,7 +315,7 @@ 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__)

8
qemu/tcg/s390/tcg-target.inc.c
View file

@ -224,6 +224,8 @@ typedef enum S390Opcode {
RX_ST = 0x50,
RX_STC = 0x42,
RX_STH = 0x40,
NOP = 0x0707,
} S390Opcode;
#ifdef CONFIG_DEBUG_TCG
@ -1721,6 +1723,12 @@ 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 (!(void*)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;