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target/i386: Fix decoding of 0xC6/0xC7 (group 11) instructions #2361

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target/i386: Fix decoding of 0xC6/0xC7 (group 11) instructions #2361

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9 changes: 3 additions & 6 deletions qemu/target/i386/translate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6009,15 +6009,12 @@ static target_ulong disas_insn(DisasContext *s, CPUState *cpu)
ot = mo_b_d(b, dflag);
modrm = x86_ldub_code(env, s);
mod = (modrm >> 6) & 3;
reg = ((modrm >> 3) & 7) | rex_r;
reg = (modrm >> 3) & 7;
if (reg != 0)
goto illegal_op;
if (mod != 3) {
if (reg != 0)
goto illegal_op;
s->rip_offset = insn_const_size(ot);
gen_lea_modrm(env, s, modrm);
} else {
if (reg != 0 && reg != 7)
goto illegal_op;
}
val = insn_get(env, s, ot);
tcg_gen_movi_tl(tcg_ctx, s->T0, val);
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 @@ -2732,6 +2732,70 @@ static void test_x86_lock_btc_reg(void)
OK(uc_close(uc));
}

static void test_x86_group_11_with_rex_r(void)
{
uc_engine *uc;

char code[] = {
// mov eax, 0x84030201
0x44, 0xc7, 0xc0, 0x01, 0x02, 0x03, 0x84,
// mov cl, 0xab
0x44, 0xc6, 0xc1, 0xab,
// mov rdx, 0xffffffff84030201
0x4c, 0xc7, 0xc2, 0x01, 0x02, 0x03, 0x84,
};

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

OK(uc_mem_map(uc, code_start + code_len, 0x1000, UC_PROT_ALL));

uint64_t rcx = 0xabcdef01;
OK(uc_reg_write(uc, UC_X86_REG_RCX, &rcx));

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

uint64_t rax = 0;
uint64_t rdx = 0;
OK(uc_reg_read(uc, UC_X86_REG_RAX, &rax));
OK(uc_reg_read(uc, UC_X86_REG_RCX, &rcx));
OK(uc_reg_read(uc, UC_X86_REG_RDX, &rdx));
TEST_CHECK(rax == 0x84030201);
TEST_CHECK(rcx == 0xabcdefab);
TEST_CHECK(rdx == 0xffffffff84030201);

OK(uc_close(uc));
}

static void test_x86_group_11_with_modrm_reg_7(void)
{
uc_engine *uc;

// Assumes that XABORT and XBEGIN are not implemented in Unicorn yet
char xbegin_code[] = {
// xbegin +0x4030201
0xc7, 0xc0 | (7 << 3), 0x01, 0x02, 0x03, 0x04
};

char xabort_code[] = {
// xabort byte 0xff
0xc6, 0xc0 | (7 << 3), 0xff
};

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

uc_assert_err(UC_ERR_INSN_INVALID,
uc_emu_start(uc, code_start, code_start + sizeof(xbegin_code), 0, 0));

OK(uc_close(uc));

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

uc_assert_err(UC_ERR_INSN_INVALID,
uc_emu_start(uc, code_start, code_start + sizeof(xabort_code), 0, 0));

OK(uc_close(uc));
}

TEST_LIST = {
{"test_x86_in", test_x86_in},
{"test_x86_out", test_x86_out},
Expand Down Expand Up @@ -2814,4 +2878,6 @@ TEST_LIST = {
{"test_x86_lock_bt_reg", test_x86_lock_bt_reg},
{"test_x86_lock_btc_mem", test_x86_lock_btc_mem},
{"test_x86_lock_btc_reg", test_x86_lock_btc_reg},
{"test_x86_group_11_with_rex_r", test_x86_group_11_with_rex_r},
{"test_x86_group_11_with_modrm_reg_7", test_x86_group_11_with_modrm_reg_7},
{NULL, NULL}};
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