Update README.md - aerc - mirror of ~rjarry's aerc fork

diff options

author	Drew DeVault <sir@cmpwn.com>	2019-03-21 22:07:03 -0400
committer	Drew DeVault <sir@cmpwn.com>	2019-03-21 22:07:03 -0400
commit	84e9853c1613f43f76bd46f0c1eb143d1db16ac2 (patch)
tree	0ef1fd2013c55a0463140dd7089b373ec5de2a12 /templates/quoted_reply
parent	e59122150932ae2cad32ab5881ed40ef0d722812 (diff)
download	aerc-84e9853c1613f43f76bd46f0c1eb143d1db16ac2.tar.gz

Update README.md

Diffstat (limited to 'templates/quoted_reply')

0 files changed, 0 insertions, 0 deletions

//: SubX mostly deals with instructions operating on 32-bit operands, but we //: still need to deal with raw bytes for strings and so on. //: Unfortunately the register encodings when dealing with bytes are a mess. //: We need a special case for them. :(code) string rname_8bit(uint8_t r) { switch (r) { case 0: return "AL"; // lowest byte of EAX case 1: return "CL"; // lowest byte of ECX case 2: return "DL"; // lowest byte of EDX case 3: return "BL"; // lowest byte of EBX case 4: return "AH"; // second lowest byte of EAX case 5: return "CH"; // second lowest byte of ECX case 6: return "DH"; // second lowest byte of EDX case 7: return "BH"; // second lowest byte of EBX default: raise << "invalid 8-bit register " << r << '\n' << end(); return ""; } } uint8_t* effective_byte_address(uint8_t modrm) { uint8_t mod = (modrm>>6); uint8_t rm = modrm & 0x7; if (mod == 3) { // select an 8-bit register trace(90, "run") << "r/m8 is " << rname_8bit(rm) << end(); return reg_8bit(rm); } // the rest is as usual return mem_addr_u8(effective_address_number(modrm)); } uint8_t* reg_8bit(uint8_t rm) { uint8_t* result = reinterpret_cast<uint8_t*>(&Reg[rm & 0x3].i); // _L register if (rm & 0x4) ++result; // _H register; assumes host is little-endian return result; } :(before "End Initialize Op Names") put_new(Name, "88", "copy r8 to r8/m8-at-r32"); :(scenario copy_r8_to_mem_at_r32) % Reg[EBX].i = 0x224488ab; % Reg[EAX].i = 0x2000; == 0x1 # op ModR/M SIB displacement immediate 88 18 # copy BL to the byte at *EAX # ModR/M in binary: 00 (indirect mode) 011 (src BL) 000 (dest EAX) == 0x2000 f0 cc bb aa # 0xf0 with more data in following bytes +run: copy BL to r8/m8-at-r32 +run: effective address is 0x00002000 (EAX) +run: storing 0xab % CHECK_EQ(0xaabbccab, read_mem_u32(0x2000)); :(before "End Single-Byte Opcodes") case 0x88: { // copy r8 to r/m8 const uint8_t modrm = next(); const uint8_t rsrc = (modrm>>3)&0x7; trace(90, "run") << "copy " << rname_8bit(rsrc) << " to r8/m8-at-r32" << end(); // use unsigned to zero-extend 8-bit value to 32 bits uint8_t* dest = reinterpret_cast<uint8_t*>(effective_byte_address(modrm)); const uint8_t* src = reg_8bit(rsrc); *dest = *src; trace(90, "run") << "storing 0x" << HEXBYTE << NUM(*dest) << end(); break; } //: :(before "End Initialize Op Names") put_new(Name, "8a", "copy r8/m8-at-r32 to r8"); :(scenario copy_mem_at_r32_to_r8) % Reg[EBX].i = 0xaabbcc0f; // one nibble each of lowest byte set to all 0s and all 1s, to maximize value of this test % Reg[EAX].i = 0x2000; == 0x1 # op ModR/M SIB displacement immediate 8a 18 # copy just the byte at *EAX to BL # ModR/M in binary: 00 (indirect mode) 011 (dest EBX) 000 (src EAX) == 0x2000 # data segment ab ff ff ff # 0xab with more data in following bytes +run: copy r8/m8-at-r32 to BL +run: effective address is 0x00002000 (EAX) +run: storing 0xab # remaining bytes of EBX are *not* cleared +run: EBX now contains 0xaabbccab :(before "End Single-Byte Opcodes") case 0x8a: { // copy r/m8 to r8 const uint8_t modrm = next(); const uint8_t rdest = (modrm>>3)&0x7; trace(90, "run") << "copy r8/m8-at-r32 to " << rname_8bit(rdest) << end(); // use unsigned to zero-extend 8-bit value to 32 bits const uint8_t* src = reinterpret_cast<uint8_t*>(effective_byte_address(modrm)); uint8_t* dest = reg_8bit(rdest); trace(90, "run") << "storing 0x" << HEXBYTE << NUM(*src) << end(); *dest = *src; const uint8_t rdest_32bit = rdest & 0x3; trace(90, "run") << rname(rdest_32bit) << " now contains 0x" << HEXWORD << Reg[rdest_32bit].u << end(); break; } :(scenario cannot_copy_byte_to_ESP_EBP_ESI_EDI) % Reg[ESI].u = 0xaabbccdd; % Reg[EBX].u = 0x11223344; == 0x1 # op ModR/M SIB displacement immediate 8a f3 # copy just the byte at *EBX to 8-bit register '6' # ModR/M in binary: 11 (direct mode) 110 (dest 8-bit 'register 6') 011 (src EBX) # ensure 8-bit register '6' is DH, not ESI +run: copy r8/m8-at-r32 to DH +run: storing 0x44 # ensure ESI is unchanged % CHECK_EQ(Reg[ESI].u, 0xaabbccdd);


context:
space:
mode: