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Update read/written registers for x86 loop instructions #2799

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1559ff4
loop
hainest Oct 4, 2025
bb19470
loope
hainest Oct 4, 2025
a041dad
loopne
hainest Oct 5, 2025
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63 changes: 35 additions & 28 deletions arch/X86/X86Mapping.c
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Original file line number Diff line number Diff line change
Expand Up @@ -942,7 +942,6 @@ void X86_get_insn_id(cs_struct *h, cs_insn *insn, unsigned int id)
}
break;
}

switch (insn->id) {
default:
break;
Expand All @@ -954,39 +953,47 @@ void X86_get_insn_id(cs_struct *h, cs_insn *insn, unsigned int id)
default:
break;
case CS_MODE_16:
insn->detail->regs_read[0] = X86_REG_CX;
insn->detail->regs_read_count = 1;
insn->detail->regs_write[0] =
X86_REG_CX;
insn->detail->regs_write_count = 1;
break;
case CS_MODE_32:
insn->detail->regs_read[0] =
X86_REG_ECX;
insn->detail->regs_read_count = 1;
insn->detail->regs_write[0] =
X86_REG_ECX;
insn->detail->regs_write_count = 1;
arr_replace(
insn->detail->regs_read,
insn->detail->regs_read_count,
X86_REG_EIP, X86_REG_IP);
arr_replace(
insn->detail->regs_write,
insn->detail->regs_write_count,
X86_REG_EIP, X86_REG_IP);
arr_replace(
insn->detail->regs_read,
insn->detail->regs_read_count,
X86_REG_ECX, X86_REG_CX);
arr_replace(
insn->detail->regs_write,
insn->detail->regs_write_count,
X86_REG_ECX, X86_REG_CX);
break;
case CS_MODE_64:
insn->detail->regs_read[0] =
X86_REG_RCX;
insn->detail->regs_read_count = 1;
insn->detail->regs_write[0] =
X86_REG_RCX;
insn->detail->regs_write_count = 1;
arr_replace(
insn->detail->regs_read,
insn->detail->regs_read_count,
X86_REG_EIP, X86_REG_RIP);
arr_replace(
insn->detail->regs_write,
insn->detail->regs_write_count,
X86_REG_EIP, X86_REG_RIP);
arr_replace(
insn->detail->regs_read,
insn->detail->regs_read_count,
X86_REG_ECX, X86_REG_RCX);
arr_replace(
insn->detail->regs_write,
insn->detail->regs_write_count,
X86_REG_ECX, X86_REG_RCX);
break;
}
}

// LOOPE & LOOPNE also read EFLAGS
if (insn->id != X86_INS_LOOP) {
insn->detail->regs_read[1] =
X86_REG_EFLAGS;
insn->detail->regs_read_count = 2;
}

switch (insn->id) {
default:
break;

case X86_INS_LODSB:
case X86_INS_LODSD:
case X86_INS_LODSQ:
Expand Down
6 changes: 3 additions & 3 deletions arch/X86/X86MappingInsn.inc
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Original file line number Diff line number Diff line change
Expand Up @@ -7937,21 +7937,21 @@
{
X86_LOOP, X86_INS_LOOP, 0,
#ifndef CAPSTONE_DIET
{ 0 }, { 0 }, { X86_GRP_BRANCH_RELATIVE, 0 }, 0, 0
{ X86_REG_EIP, X86_REG_ECX, 0 }, { X86_REG_EIP, X86_REG_ECX, 0 }, { X86_GRP_BRANCH_RELATIVE, 0 }, 0, 0
#endif
},

{
X86_LOOPE, X86_INS_LOOPE, 0,
#ifndef CAPSTONE_DIET
{ 0 }, { 0 }, { X86_GRP_BRANCH_RELATIVE, 0 }, 0, 0
{ X86_REG_EIP, X86_REG_ECX, X86_REG_EFLAGS, 0 }, { X86_REG_EIP, X86_REG_ECX, 0 }, { X86_GRP_BRANCH_RELATIVE, 0 }, 0, 0
#endif
},

{
X86_LOOPNE, X86_INS_LOOPNE, 0,
#ifndef CAPSTONE_DIET
{ 0 }, { 0 }, { X86_GRP_BRANCH_RELATIVE, 0 }, 0, 0
{ X86_REG_EIP, X86_REG_ECX, X86_REG_EFLAGS, 0 }, { X86_REG_EIP, X86_REG_ECX, 0 }, { X86_GRP_BRANCH_RELATIVE, 0 }, 0, 0
#endif
},

Expand Down
6 changes: 3 additions & 3 deletions arch/X86/X86MappingInsn_reduce.inc
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Original file line number Diff line number Diff line change
Expand Up @@ -4472,21 +4472,21 @@
{
X86_LOOP, X86_INS_LOOP, 0,
#ifndef CAPSTONE_DIET
{ 0 }, { 0 }, { 0 }, 0, 0
{ X86_REG_EIP, X86_REG_ECX, 0 }, { X86_REG_EIP, X86_REG_ECX, 0 }, { X86_GRP_BRANCH_RELATIVE, 0 }, 0, 0
#endif
},

{
X86_LOOPE, X86_INS_LOOPE, 0,
#ifndef CAPSTONE_DIET
{ 0 }, { 0 }, { 0 }, 0, 0
{ X86_REG_EIP, X86_REG_ECX, X86_REG_EFLAGS, 0 }, { X86_REG_EIP, X86_REG_ECX, 0 }, { X86_GRP_BRANCH_RELATIVE, 0 }, 0, 0
#endif
},

{
X86_LOOPNE, X86_INS_LOOPNE, 0,
#ifndef CAPSTONE_DIET
{ 0 }, { 0 }, { 0 }, 0, 0
{ X86_REG_EIP, X86_REG_ECX, X86_REG_EFLAGS, 0 }, { X86_REG_EIP, X86_REG_ECX, 0 }, { X86_GRP_BRANCH_RELATIVE, 0 }, 0, 0
#endif
},

Expand Down
178 changes: 178 additions & 0 deletions tests/details/x86.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -5933,3 +5933,181 @@ test_cases:
eflags: [ X86_EFLAGS_TEST_OF, X86_EFLAGS_TEST_SF, X86_EFLAGS_TEST_ZF ]
regs_read: [ rflags, rip ]
regs_write: [ rip ]

-
input:
name: "Loop according to ECX count, 16-bit decode mode"
bytes: [
0xe2, 0x32, # loop 0x34
0xe1, 0x30, # loope 0x34
0xe0, 0x2e, # loopne 0x34
]
arch: "x86"
options: [ CS_OPT_DETAIL, CS_MODE_16 ]
expected:
insns:
-
asm_text: "loop 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe2, 0x00, 0x00, 0x00 ]
regs_read: [ ip, cx ]
regs_write: [ ip, cx ]
-
asm_text: "loope 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe1, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ ip, cx, flags ]
regs_write: [ ip, cx ]
-
asm_text: "loopne 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe0, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ ip, cx, flags ]
regs_write: [ ip, cx ]

-
input:
name: "Loop according to ECX count, 32-bit decode mode"
bytes: [
0xe2, 0x32, # loop 0x34
0xe1, 0x30, # loope 0x34
0xe0, 0x2e, # loopne 0x34
]
arch: "x86"
options: [ CS_OPT_DETAIL, CS_MODE_32 ]
expected:
insns:
-
asm_text: "loop 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe2, 0x00, 0x00, 0x00 ]
regs_read: [ eip, ecx ]
regs_write: [ eip, ecx ]
-
asm_text: "loope 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe1, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ eip, ecx, eflags ]
regs_write: [ eip, ecx ]
-
asm_text: "loopne 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe0, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ eip, ecx, eflags ]
regs_write: [ eip, ecx ]

-
input:
name: "Loop according to ECX count, 64-bit decode mode"
bytes: [
0xe2, 0x32, # loop 0x34
0x48, 0xe2, 0x2f, # REX.W loop 0x34 (should ignore REX)
0x67, 0xe2, 0x2c, # loop 0x34 (with size override)
0xe1, 0x2a, # loope 0x34
0x48, 0xe1, 0x27, # REX.W loop 0x34 (should ignore REX)
0x67, 0xe1, 0x24, # loop 0x34 (with size override)
0xe0, 0x22, # loope 0x34
0x48, 0xe0, 0x1f, # REX.W loop 0x34 (should ignore REX)
0x67, 0xe0, 0x1c, # loop 0x34 (with size override)
]
arch: "x86"
options: [ CS_OPT_DETAIL, CS_MODE_64 ]
expected:
insns:
-
asm_text: "loop 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe2, 0x00, 0x00, 0x00 ]
regs_read: [ rip, rcx ]
regs_write: [ rip, rcx ]
-
asm_text: "loop 0x34"
details:
x86:
rex: 0x48
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe2, 0x00, 0x00, 0x00 ]
regs_read: [ rip, rcx ]
regs_write: [ rip, rcx ]
-
asm_text: "loop 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_ADDRSIZE ]
opcode: [ 0xe2, 0x00, 0x00, 0x00 ]
regs_read: [ rip, rcx ]
regs_write: [ rip, rcx ] # BUG: should be ecx
-
asm_text: "loope 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe1, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ rip, rcx, rflags ]
regs_write: [ rip, rcx ]
-
asm_text: "loope 0x34"
details:
x86:
rex: 0x48
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe1, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ rip, rcx, rflags ]
regs_write: [ rip, rcx ]
-
asm_text: "loope 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_ADDRSIZE ]
opcode: [ 0xe1, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ rip, rcx, rflags ]
regs_write: [ rip, rcx ] # BUG: should be ecx
-
asm_text: "loopne 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe0, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ rip, rcx, rflags ]
regs_write: [ rip, rcx ]
-
asm_text: "loopne 0x34"
details:
x86:
rex: 0x48
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0 ]
opcode: [ 0xe0, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ rip, rcx, rflags ]
regs_write: [ rip, rcx ]
-
asm_text: "loopne 0x34"
details:
x86:
prefix: [ X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_0, X86_PREFIX_ADDRSIZE ]
opcode: [ 0xe0, 0x00, 0x00, 0x00 ]
eflags: [ X86_EFLAGS_TEST_ZF ]
regs_read: [ rip, rcx, rflags ]
regs_write: [ rip, rcx ] # BUG: should be ecx
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