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hv: instr_emul: refine decode_prefixes to one exit point

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Misra C requires Function must have only one return entry.

Tracked-On: #861
Signed-off-by: Li, Fei1 <fei1.li@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
This commit is contained in:
Li, Fei1 2019-01-11 08:12:02 +08:00 committed by wenlingz
parent 433a492a4e
commit 5e38e0ffd6
1 changed files with 65 additions and 61 deletions
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126
hypervisor/arch/x86/guest/instr_emul.c
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@ -1698,76 +1698,80 @@ static bool segment_override(uint8_t x, enum cpu_reg_name *seg)
return override;
}
static int32_t decode_prefixes(struct instr_emul_vie *vie,
enum vm_cpu_mode cpu_mode, bool cs_d)
static int32_t decode_prefixes(struct instr_emul_vie *vie, enum vm_cpu_mode cpu_mode, bool cs_d)
{
uint8_t x, i;
int32_t ret = 0;
for (i = 0U; i < VIE_PREFIX_SIZE; i++) {
if (vie_peek(vie, &x) != 0) {
return -1;
}
if (x == 0x66U) {
vie->opsize_override = 1U;
} else if (x == 0x67U) {
vie->addrsize_override = 1U;
} else if (x == 0xF3U) {
vie->repz_present = 1U;
} else if (x == 0xF2U) {
vie->repnz_present = 1U;
} else if (segment_override(x, &vie->segment_register)) {
vie->seg_override = 1U;
} else {
ret = -1;
break;
}
vie_advance(vie);
}
/*
* From section 2.2.1, "REX Prefixes", Intel SDM Vol 2:
* - Only one REX prefix is allowed per instruction.
* - The REX prefix must immediately precede the opcode byte or the
* escape opcode byte.
* - If an instruction has a mandatory prefix (0x66, 0xF2 or 0xF3)
* the mandatory prefix must come before the REX prefix.
*/
if ((cpu_mode == CPU_MODE_64BIT) && (x >= 0x40U) && (x <= 0x4FU)) {
vie->rex_present = 1U;
vie->rex_w = (x & 0x8U) != 0U ? 1U : 0U;
vie->rex_r = (x & 0x4U) != 0U ? 1U : 0U;
vie->rex_x = (x & 0x2U) != 0U ? 1U : 0U;
vie->rex_b = (x & 0x1U) != 0U ? 1U : 0U;
vie_advance(vie);
}
/*
* Section "Operand-Size And Address-Size Attributes", Intel SDM, Vol 1
*/
if (cpu_mode == CPU_MODE_64BIT) {
/*
* Default address size is 64-bits and default operand size
* is 32-bits.
*/
vie->addrsize = (vie->addrsize_override != 0U)? 4U : 8U;
if (vie->rex_w != 0U) {
vie->opsize = 8U;
} else if (vie->opsize_override != 0U) {
vie->opsize = 2U;
} else {
vie->opsize = 4U;
if (x == 0x66U) {
vie->opsize_override = 1U;
} else if (x == 0x67U) {
vie->addrsize_override = 1U;
} else if (x == 0xF3U) {
vie->repz_present = 1U;
} else if (x == 0xF2U) {
vie->repnz_present = 1U;
} else if (segment_override(x, &vie->segment_register)) {
vie->seg_override = 1U;
} else {
break;
}
vie_advance(vie);
}
} else if (cs_d) {
/* Default address and operand sizes are 32-bits */
vie->addrsize = vie->addrsize_override != 0U ? 2U : 4U;
vie->opsize = vie->opsize_override != 0U ? 2U : 4U;
} else {
/* Default address and operand sizes are 16-bits */
vie->addrsize = vie->addrsize_override != 0U ? 4U : 2U;
vie->opsize = vie->opsize_override != 0U ? 4U : 2U;
}
return 0;
if (ret == 0) {
/*
* From section 2.2.1, "REX Prefixes", Intel SDM Vol 2:
* - Only one REX prefix is allowed per instruction.
* - The REX prefix must immediately precede the opcode byte or the
* escape opcode byte.
* - If an instruction has a mandatory prefix (0x66, 0xF2 or 0xF3)
* the mandatory prefix must come before the REX prefix.
*/
if ((cpu_mode == CPU_MODE_64BIT) && (x >= 0x40U) && (x <= 0x4FU)) {
vie->rex_present = 1U;
vie->rex_w = (x & 0x8U) != 0U ? 1U : 0U;
vie->rex_r = (x & 0x4U) != 0U ? 1U : 0U;
vie->rex_x = (x & 0x2U) != 0U ? 1U : 0U;
vie->rex_b = (x & 0x1U) != 0U ? 1U : 0U;
vie_advance(vie);
}
/*
* Section "Operand-Size And Address-Size Attributes", Intel SDM, Vol 1
*/
if (cpu_mode == CPU_MODE_64BIT) {
/*
* Default address size is 64-bits and default operand size
* is 32-bits.
*/
vie->addrsize = (vie->addrsize_override != 0U)? 4U : 8U;
if (vie->rex_w != 0U) {
vie->opsize = 8U;
} else if (vie->opsize_override != 0U) {
vie->opsize = 2U;
} else {
vie->opsize = 4U;
}
} else if (cs_d) {
/* Default address and operand sizes are 32-bits */
vie->addrsize = vie->addrsize_override != 0U ? 2U : 4U;
vie->opsize = vie->opsize_override != 0U ? 2U : 4U;
} else {
/* Default address and operand sizes are 16-bits */
vie->addrsize = vie->addrsize_override != 0U ? 4U : 2U;
vie->opsize = vie->opsize_override != 0U ? 4U : 2U;
}
}
return ret;
}
static int32_t decode_two_byte_opcode(struct instr_emul_vie *vie)