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target/i386: Clear s->x86_64_hregs when decoding LAHF/SAHF with a REX prefix #2370

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target/i386: Clear s->x86_64_hregs when decoding LAHF/SAHF with a REX prefix #2370

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6 changes: 4 additions & 2 deletions qemu/target/i386/translate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5037,8 +5037,10 @@ static target_ulong disas_insn(DisasContext *s, CPUState *cpu)
rex_r = (rex_byte & 0x4) << 1;
s->rex_x = (rex_byte & 0x2) << 2;
REX_B(s) = (rex_byte & 0x1) << 3;
/* select uniform byte register addressing */
s->x86_64_hregs = true;
/* select uniform byte register addressing
* only when not decoding LAHF (0x9f) / SAHF (0x9e)
*/
s->x86_64_hregs = (b & 0x9e) != 0x9e;
}

/* In 64-bit mode, the default data size is 32-bit. Select 64-bit
Expand Down
66 changes: 66 additions & 0 deletions tests/unit/test_x86.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2618,6 +2618,70 @@ static void test_x86_aas_flags(void)
OK(uc_close(uc));
}

static void test_x86_lahf_with_rex(void)
{
uc_engine *uc;

char code[] = {
// lahf
0x40, 0x9f
};

uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_64, code, sizeof(code));

uint64_t rax = 0x1122334455667788;
uint64_t rsp = 0;
uint64_t rflags = 0x246;

OK(uc_reg_write(uc, UC_X86_REG_RAX, &rax));
OK(uc_reg_write(uc, UC_X86_REG_RSP, &rsp));
OK(uc_reg_write(uc, UC_X86_REG_RFLAGS, &rflags));

OK(uc_emu_start(uc, code_start, code_start + sizeof(code), 0, 0));

OK(uc_reg_read(uc, UC_X86_REG_RAX, &rax));
OK(uc_reg_read(uc, UC_X86_REG_RSP, &rsp));
OK(uc_reg_read(uc, UC_X86_REG_RFLAGS, &rflags));

TEST_CHECK(rax == 0x1122334455664688);
TEST_CHECK(rsp == 0);
TEST_CHECK(rflags == 0x246);

OK(uc_close(uc));
}

static void test_x86_sahf_with_rex(void)
{
uc_engine *uc;

char code[] = {
// sahf
0x40, 0x9e
};

uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_64, code, sizeof(code));

uint64_t rax = 0xff << 8;
uint64_t rsp = 0;
uint64_t rflags = 2;

OK(uc_reg_write(uc, UC_X86_REG_RAX, &rax));
OK(uc_reg_write(uc, UC_X86_REG_RSP, &rsp));
OK(uc_reg_write(uc, UC_X86_REG_RFLAGS, &rflags));

OK(uc_emu_start(uc, code_start, code_start + sizeof(code), 0, 0));

OK(uc_reg_read(uc, UC_X86_REG_RAX, &rax));
OK(uc_reg_read(uc, UC_X86_REG_RSP, &rsp));
OK(uc_reg_read(uc, UC_X86_REG_RFLAGS, &rflags));

TEST_CHECK(rax == 0xff << 8);
TEST_CHECK(rsp == 0);
TEST_CHECK(rflags == 0xd7);

OK(uc_close(uc));
}

static void test_x86_group_1a(void)
{
uc_engine *uc;
Expand Down Expand Up @@ -2809,6 +2873,8 @@ TEST_LIST = {
{"test_x86_mem_hooks_pc_guarantee", test_x86_mem_hooks_pc_guarantee},
{"test_x86_aaa_flags", test_x86_aaa_flags},
{"test_x86_aas_flags", test_x86_aas_flags},
{"test_x86_lahf_with_rex", test_x86_lahf_with_rex},
{"test_x86_sahf_with_rex", test_x86_sahf_with_rex},
{"test_x86_group_1a", test_x86_group_1a},
{"test_x86_lock_bt_mem", test_x86_lock_bt_mem},
{"test_x86_lock_bt_reg", test_x86_lock_bt_reg},
Expand Down
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