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compact-unwind-dumper.c
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#include <fcntl.h>
#include <inttypes.h>
#include <mach-o/compact_unwind_encoding.h>
#include <mach-o/loader.h>
#include <mach-o/nlist.h>
#include <mach/machine.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/errno.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#define EXTRACT_BITS(value, mask) \
((value >> __builtin_ctz(mask)) & (((1 << __builtin_popcount(mask))) - 1))
// A quick sketch of a program which can parse the compact unwind info
// used on Darwin systems for exception handling. The output of
// unwinddump will be more authoritative/reliable but this program
// can dump at least the UNWIND_X86_64_MODE_RBP_FRAME format entries
// correctly.
struct symbol {
uint64_t file_address;
const char *name;
};
int symbol_compare(const void *a, const void *b) {
return (int)((struct symbol *)a)->file_address -
((struct symbol *)b)->file_address;
}
struct baton {
cpu_type_t cputype;
uint8_t *mach_header_start; // pointer into this program's address space
uint8_t *compact_unwind_start; // pointer into this program's address space
int addr_size; // 4 or 8 bytes, the size of addresses in this file
uint64_t text_segment_vmaddr; // __TEXT segment vmaddr
uint64_t text_segment_file_offset;
uint64_t text_section_vmaddr; // __TEXT,__text section vmaddr
uint64_t text_section_file_offset;
uint64_t eh_section_file_address; // the file address of the __TEXT,__eh_frame
// section
uint8_t
*lsda_array_start; // for the currently-being-processed first-level index
uint8_t
*lsda_array_end; // the lsda_array_start for the NEXT first-level index
struct symbol *symbols;
int symbols_count;
uint64_t *function_start_addresses;
int function_start_addresses_count;
int current_index_table_number;
struct unwind_info_section_header unwind_header;
struct unwind_info_section_header_index_entry first_level_index_entry;
struct unwind_info_compressed_second_level_page_header
compressed_second_level_page_header;
struct unwind_info_regular_second_level_page_header
regular_second_level_page_header;
};
uint64_t read_leb128(uint8_t **offset) {
uint64_t result = 0;
int shift = 0;
while (1) {
uint8_t byte = **offset;
*offset = *offset + 1;
result |= (byte & 0x7f) << shift;
if ((byte & 0x80) == 0)
break;
shift += 7;
}
return result;
}
// step through the load commands in a thin mach-o binary,
// find the cputype and the start of the __TEXT,__unwind_info
// section, return a pointer to that section or NULL if not found.
static void scan_macho_load_commands(struct baton *baton) {
struct symtab_command symtab_cmd;
uint64_t linkedit_segment_vmaddr;
uint64_t linkedit_segment_file_offset;
baton->compact_unwind_start = 0;
uint32_t *magic = (uint32_t *)baton->mach_header_start;
if (*magic != MH_MAGIC && *magic != MH_MAGIC_64) {
printf("Unexpected magic number 0x%x in header, exiting.", *magic);
exit(1);
}
bool is_64bit = false;
if (*magic == MH_MAGIC_64)
is_64bit = true;
uint8_t *offset = baton->mach_header_start;
struct mach_header mh;
memcpy(&mh, offset, sizeof(struct mach_header));
if (is_64bit)
offset += sizeof(struct mach_header_64);
else
offset += sizeof(struct mach_header);
if (is_64bit)
baton->addr_size = 8;
else
baton->addr_size = 4;
baton->cputype = mh.cputype;
uint8_t *start_of_load_commands = offset;
uint32_t cur_cmd = 0;
while (cur_cmd < mh.ncmds &&
(offset - start_of_load_commands) < mh.sizeofcmds) {
struct load_command lc;
uint32_t *lc_cmd = (uint32_t *)offset;
uint32_t *lc_cmdsize = (uint32_t *)offset + 1;
uint8_t *start_of_this_load_cmd = offset;
if (*lc_cmd == LC_SEGMENT || *lc_cmd == LC_SEGMENT_64) {
char segment_name[17];
segment_name[0] = '\0';
uint32_t nsects = 0;
uint64_t segment_offset = 0;
uint64_t segment_vmaddr = 0;
if (*lc_cmd == LC_SEGMENT_64) {
struct segment_command_64 seg;
memcpy(&seg, offset, sizeof(struct segment_command_64));
memcpy(&segment_name, &seg.segname, 16);
segment_name[16] = '\0';
nsects = seg.nsects;
segment_offset = seg.fileoff;
segment_vmaddr = seg.vmaddr;
offset += sizeof(struct segment_command_64);
if ((seg.flags & SG_PROTECTED_VERSION_1) == SG_PROTECTED_VERSION_1) {
printf("Segment '%s' is encrypted.\n", segment_name);
}
}
if (*lc_cmd == LC_SEGMENT) {
struct segment_command seg;
memcpy(&seg, offset, sizeof(struct segment_command));
memcpy(&segment_name, &seg.segname, 16);
segment_name[16] = '\0';
nsects = seg.nsects;
segment_offset = seg.fileoff;
segment_vmaddr = seg.vmaddr;
offset += sizeof(struct segment_command);
if ((seg.flags & SG_PROTECTED_VERSION_1) == SG_PROTECTED_VERSION_1) {
printf("Segment '%s' is encrypted.\n", segment_name);
}
}
if (nsects != 0 && strcmp(segment_name, "__TEXT") == 0) {
baton->text_segment_vmaddr = segment_vmaddr;
baton->text_segment_file_offset = segment_offset;
uint32_t current_sect = 0;
while (current_sect < nsects &&
(offset - start_of_this_load_cmd) < *lc_cmdsize) {
char sect_name[17];
memcpy(§_name, offset, 16);
sect_name[16] = '\0';
if (strcmp(sect_name, "__unwind_info") == 0) {
if (is_64bit) {
struct section_64 sect;
memset(§, 0, sizeof(struct section_64));
memcpy(§, offset, sizeof(struct section_64));
baton->compact_unwind_start =
baton->mach_header_start + sect.offset;
} else {
struct section sect;
memset(§, 0, sizeof(struct section));
memcpy(§, offset, sizeof(struct section));
baton->compact_unwind_start =
baton->mach_header_start + sect.offset;
}
}
if (strcmp(sect_name, "__eh_frame") == 0) {
if (is_64bit) {
struct section_64 sect;
memset(§, 0, sizeof(struct section_64));
memcpy(§, offset, sizeof(struct section_64));
baton->eh_section_file_address = sect.addr;
} else {
struct section sect;
memset(§, 0, sizeof(struct section));
memcpy(§, offset, sizeof(struct section));
baton->eh_section_file_address = sect.addr;
}
}
if (strcmp(sect_name, "__text") == 0) {
if (is_64bit) {
struct section_64 sect;
memset(§, 0, sizeof(struct section_64));
memcpy(§, offset, sizeof(struct section_64));
baton->text_section_vmaddr = sect.addr;
baton->text_section_file_offset = sect.offset;
} else {
struct section sect;
memset(§, 0, sizeof(struct section));
memcpy(§, offset, sizeof(struct section));
baton->text_section_vmaddr = sect.addr;
}
}
if (is_64bit) {
offset += sizeof(struct section_64);
} else {
offset += sizeof(struct section);
}
}
}
if (strcmp(segment_name, "__LINKEDIT") == 0) {
linkedit_segment_vmaddr = segment_vmaddr;
linkedit_segment_file_offset = segment_offset;
}
}
if (*lc_cmd == LC_SYMTAB) {
memcpy(&symtab_cmd, offset, sizeof(struct symtab_command));
}
if (*lc_cmd == LC_DYSYMTAB) {
struct dysymtab_command dysymtab_cmd;
memcpy(&dysymtab_cmd, offset, sizeof(struct dysymtab_command));
int nlist_size = 12;
if (is_64bit)
nlist_size = 16;
char *string_table =
(char *)(baton->mach_header_start + symtab_cmd.stroff);
uint8_t *local_syms = baton->mach_header_start + symtab_cmd.symoff +
(dysymtab_cmd.ilocalsym * nlist_size);
int local_syms_count = dysymtab_cmd.nlocalsym;
uint8_t *exported_syms = baton->mach_header_start + symtab_cmd.symoff +
(dysymtab_cmd.iextdefsym * nlist_size);
int exported_syms_count = dysymtab_cmd.nextdefsym;
// We're only going to create records for a small number of these symbols
// but to
// simplify the memory management I'll allocate enough space to store all
// of them.
baton->symbols = (struct symbol *)malloc(
sizeof(struct symbol) * (local_syms_count + exported_syms_count));
baton->symbols_count = 0;
for (int i = 0; i < local_syms_count; i++) {
struct nlist_64 nlist;
memset(&nlist, 0, sizeof(struct nlist_64));
if (is_64bit) {
memcpy(&nlist, local_syms + (i * nlist_size),
sizeof(struct nlist_64));
} else {
struct nlist nlist_32;
memset(&nlist_32, 0, sizeof(struct nlist));
memcpy(&nlist_32, local_syms + (i * nlist_size),
sizeof(struct nlist));
nlist.n_un.n_strx = nlist_32.n_un.n_strx;
nlist.n_type = nlist_32.n_type;
nlist.n_sect = nlist_32.n_sect;
nlist.n_desc = nlist_32.n_desc;
nlist.n_value = nlist_32.n_value;
}
if ((nlist.n_type & N_STAB) == 0 &&
((nlist.n_type & N_EXT) == 1 ||
((nlist.n_type & N_TYPE) == N_TYPE && nlist.n_sect != NO_SECT)) &&
nlist.n_value != 0 && nlist.n_value != baton->text_segment_vmaddr) {
baton->symbols[baton->symbols_count].file_address = nlist.n_value;
if (baton->cputype == CPU_TYPE_ARM)
baton->symbols[baton->symbols_count].file_address =
baton->symbols[baton->symbols_count].file_address & ~1;
baton->symbols[baton->symbols_count].name =
string_table + nlist.n_un.n_strx;
baton->symbols_count++;
}
}
for (int i = 0; i < exported_syms_count; i++) {
struct nlist_64 nlist;
memset(&nlist, 0, sizeof(struct nlist_64));
if (is_64bit) {
memcpy(&nlist, exported_syms + (i * nlist_size),
sizeof(struct nlist_64));
} else {
struct nlist nlist_32;
memcpy(&nlist_32, exported_syms + (i * nlist_size),
sizeof(struct nlist));
nlist.n_un.n_strx = nlist_32.n_un.n_strx;
nlist.n_type = nlist_32.n_type;
nlist.n_sect = nlist_32.n_sect;
nlist.n_desc = nlist_32.n_desc;
nlist.n_value = nlist_32.n_value;
}
if ((nlist.n_type & N_STAB) == 0 &&
((nlist.n_type & N_EXT) == 1 ||
((nlist.n_type & N_TYPE) == N_TYPE && nlist.n_sect != NO_SECT)) &&
nlist.n_value != 0 && nlist.n_value != baton->text_segment_vmaddr) {
baton->symbols[baton->symbols_count].file_address = nlist.n_value;
if (baton->cputype == CPU_TYPE_ARM)
baton->symbols[baton->symbols_count].file_address =
baton->symbols[baton->symbols_count].file_address & ~1;
baton->symbols[baton->symbols_count].name =
string_table + nlist.n_un.n_strx;
baton->symbols_count++;
}
}
qsort(baton->symbols, baton->symbols_count, sizeof(struct symbol),
symbol_compare);
}
if (*lc_cmd == LC_FUNCTION_STARTS) {
struct linkedit_data_command function_starts_cmd;
memcpy(&function_starts_cmd, offset,
sizeof(struct linkedit_data_command));
uint8_t *funcstarts_offset =
baton->mach_header_start + function_starts_cmd.dataoff;
uint8_t *function_end = funcstarts_offset + function_starts_cmd.datasize;
int count = 0;
while (funcstarts_offset < function_end) {
if (read_leb128(&funcstarts_offset) != 0) {
count++;
}
}
baton->function_start_addresses =
(uint64_t *)malloc(sizeof(uint64_t) * count);
baton->function_start_addresses_count = count;
funcstarts_offset =
baton->mach_header_start + function_starts_cmd.dataoff;
uint64_t current_pc = baton->text_segment_vmaddr;
int i = 0;
while (funcstarts_offset < function_end) {
uint64_t func_start = read_leb128(&funcstarts_offset);
if (func_start != 0) {
current_pc += func_start;
baton->function_start_addresses[i++] = current_pc;
}
}
}
offset = start_of_this_load_cmd + *lc_cmdsize;
cur_cmd++;
}
// Augment the symbol table with the function starts table -- adding symbol
// entries
// for functions that were stripped.
int unnamed_functions_to_add = 0;
for (int i = 0; i < baton->function_start_addresses_count; i++) {
struct symbol search_key;
search_key.file_address = baton->function_start_addresses[i];
if (baton->cputype == CPU_TYPE_ARM)
search_key.file_address = search_key.file_address & ~1;
struct symbol *sym =
bsearch(&search_key, baton->symbols, baton->symbols_count,
sizeof(struct symbol), symbol_compare);
if (sym == NULL)
unnamed_functions_to_add++;
}
baton->symbols = (struct symbol *)realloc(
baton->symbols, sizeof(struct symbol) *
(baton->symbols_count + unnamed_functions_to_add));
int current_unnamed_symbol = 1;
int number_symbols_added = 0;
for (int i = 0; i < baton->function_start_addresses_count; i++) {
struct symbol search_key;
search_key.file_address = baton->function_start_addresses[i];
if (baton->cputype == CPU_TYPE_ARM)
search_key.file_address = search_key.file_address & ~1;
struct symbol *sym =
bsearch(&search_key, baton->symbols, baton->symbols_count,
sizeof(struct symbol), symbol_compare);
if (sym == NULL) {
char *name;
asprintf(&name, "unnamed function #%d", current_unnamed_symbol++);
baton->symbols[baton->symbols_count + number_symbols_added].file_address =
baton->function_start_addresses[i];
baton->symbols[baton->symbols_count + number_symbols_added].name = name;
number_symbols_added++;
}
}
baton->symbols_count += number_symbols_added;
qsort(baton->symbols, baton->symbols_count, sizeof(struct symbol),
symbol_compare);
// printf ("function start addresses\n");
// for (int i = 0; i < baton->function_start_addresses_count; i++)
// {
// printf ("0x%012llx\n", baton->function_start_addresses[i]);
// }
// printf ("symbol table names & addresses\n");
// for (int i = 0; i < baton->symbols_count; i++)
// {
// printf ("0x%012llx %s\n", baton->symbols[i].file_address,
// baton->symbols[i].name);
// }
}
void print_encoding_x86_64(struct baton baton, uint8_t *function_start,
uint32_t encoding) {
int mode = encoding & UNWIND_X86_64_MODE_MASK;
switch (mode) {
case UNWIND_X86_64_MODE_RBP_FRAME: {
printf("frame func: CFA is rbp+%d ", 16);
printf(" rip=[CFA-8] rbp=[CFA-16]");
uint32_t saved_registers_offset =
EXTRACT_BITS(encoding, UNWIND_X86_64_RBP_FRAME_OFFSET);
uint32_t saved_registers_locations =
EXTRACT_BITS(encoding, UNWIND_X86_64_RBP_FRAME_REGISTERS);
saved_registers_offset += 2;
for (int i = 0; i < 5; i++) {
switch (saved_registers_locations & 0x7) {
case UNWIND_X86_64_REG_NONE:
break;
case UNWIND_X86_64_REG_RBX:
printf(" rbx=[CFA-%d]", saved_registers_offset * 8);
break;
case UNWIND_X86_64_REG_R12:
printf(" r12=[CFA-%d]", saved_registers_offset * 8);
break;
case UNWIND_X86_64_REG_R13:
printf(" r13=[CFA-%d]", saved_registers_offset * 8);
break;
case UNWIND_X86_64_REG_R14:
printf(" r14=[CFA-%d]", saved_registers_offset * 8);
break;
case UNWIND_X86_64_REG_R15:
printf(" r15=[CFA-%d]", saved_registers_offset * 8);
break;
}
saved_registers_offset--;
saved_registers_locations >>= 3;
}
} break;
case UNWIND_X86_64_MODE_STACK_IND:
case UNWIND_X86_64_MODE_STACK_IMMD: {
uint32_t stack_size =
EXTRACT_BITS(encoding, UNWIND_X86_64_FRAMELESS_STACK_SIZE);
uint32_t register_count =
EXTRACT_BITS(encoding, UNWIND_X86_64_FRAMELESS_STACK_REG_COUNT);
uint32_t permutation =
EXTRACT_BITS(encoding, UNWIND_X86_64_FRAMELESS_STACK_REG_PERMUTATION);
if (mode == UNWIND_X86_64_MODE_STACK_IND && function_start) {
uint32_t stack_adjust =
EXTRACT_BITS(encoding, UNWIND_X86_64_FRAMELESS_STACK_ADJUST);
// offset into the function instructions; 0 == beginning of first
// instruction
uint32_t offset_to_subl_insn =
EXTRACT_BITS(encoding, UNWIND_X86_64_FRAMELESS_STACK_SIZE);
stack_size = *((uint32_t *)(function_start + offset_to_subl_insn));
stack_size += stack_adjust * 8;
printf("large stack ");
}
if (mode == UNWIND_X86_64_MODE_STACK_IND) {
printf("frameless function: stack size %d, register count %d ",
stack_size * 8, register_count);
} else {
printf("frameless function: stack size %d, register count %d ",
stack_size, register_count);
}
if (register_count == 0) {
printf(" no registers saved");
} else {
// We need to include (up to) 6 registers in 10 bits.
// That would be 18 bits if we just used 3 bits per reg to indicate
// the order they're saved on the stack.
//
// This is done with Lehmer code permutation, e.g. see
// http://stackoverflow.com/questions/1506078/fast-permutation-number-permutation-mapping-algorithms
int permunreg[6];
// This decodes the variable-base number in the 10 bits
// and gives us the Lehmer code sequence which can then
// be decoded.
switch (register_count) {
case 6:
permunreg[0] = permutation / 120; // 120 == 5!
permutation -= (permunreg[0] * 120);
permunreg[1] = permutation / 24; // 24 == 4!
permutation -= (permunreg[1] * 24);
permunreg[2] = permutation / 6; // 6 == 3!
permutation -= (permunreg[2] * 6);
permunreg[3] = permutation / 2; // 2 == 2!
permutation -= (permunreg[3] * 2);
permunreg[4] = permutation; // 1 == 1!
permunreg[5] = 0;
break;
case 5:
permunreg[0] = permutation / 120;
permutation -= (permunreg[0] * 120);
permunreg[1] = permutation / 24;
permutation -= (permunreg[1] * 24);
permunreg[2] = permutation / 6;
permutation -= (permunreg[2] * 6);
permunreg[3] = permutation / 2;
permutation -= (permunreg[3] * 2);
permunreg[4] = permutation;
break;
case 4:
permunreg[0] = permutation / 60;
permutation -= (permunreg[0] * 60);
permunreg[1] = permutation / 12;
permutation -= (permunreg[1] * 12);
permunreg[2] = permutation / 3;
permutation -= (permunreg[2] * 3);
permunreg[3] = permutation;
break;
case 3:
permunreg[0] = permutation / 20;
permutation -= (permunreg[0] * 20);
permunreg[1] = permutation / 4;
permutation -= (permunreg[1] * 4);
permunreg[2] = permutation;
break;
case 2:
permunreg[0] = permutation / 5;
permutation -= (permunreg[0] * 5);
permunreg[1] = permutation;
break;
case 1:
permunreg[0] = permutation;
break;
}
// Decode the Lehmer code for this permutation of
// the registers v. http://en.wikipedia.org/wiki/Lehmer_code
int registers[6];
bool used[7] = {false, false, false, false, false, false, false};
for (int i = 0; i < register_count; i++) {
int renum = 0;
for (int j = 1; j < 7; j++) {
if (used[j] == false) {
if (renum == permunreg[i]) {
registers[i] = j;
used[j] = true;
break;
}
renum++;
}
}
}
if (mode == UNWIND_X86_64_MODE_STACK_IND) {
printf(" CFA is rsp+%d ", stack_size);
} else {
printf(" CFA is rsp+%d ", stack_size * 8);
}
uint32_t saved_registers_offset = 1;
printf(" rip=[CFA-%d]", saved_registers_offset * 8);
saved_registers_offset++;
for (int i = (sizeof(registers) / sizeof(int)) - 1; i >= 0; i--) {
switch (registers[i]) {
case UNWIND_X86_64_REG_NONE:
break;
case UNWIND_X86_64_REG_RBX:
printf(" rbx=[CFA-%d]", saved_registers_offset * 8);
saved_registers_offset++;
break;
case UNWIND_X86_64_REG_R12:
printf(" r12=[CFA-%d]", saved_registers_offset * 8);
saved_registers_offset++;
break;
case UNWIND_X86_64_REG_R13:
printf(" r13=[CFA-%d]", saved_registers_offset * 8);
saved_registers_offset++;
break;
case UNWIND_X86_64_REG_R14:
printf(" r14=[CFA-%d]", saved_registers_offset * 8);
saved_registers_offset++;
break;
case UNWIND_X86_64_REG_R15:
printf(" r15=[CFA-%d]", saved_registers_offset * 8);
saved_registers_offset++;
break;
case UNWIND_X86_64_REG_RBP:
printf(" rbp=[CFA-%d]", saved_registers_offset * 8);
saved_registers_offset++;
break;
}
}
}
} break;
case UNWIND_X86_64_MODE_DWARF: {
uint32_t dwarf_offset = encoding & UNWIND_X86_DWARF_SECTION_OFFSET;
printf(
"DWARF unwind instructions: FDE at offset %d (file address 0x%" PRIx64
")",
dwarf_offset, dwarf_offset + baton.eh_section_file_address);
} break;
case 0: {
printf(" no unwind information");
} break;
}
}
void print_encoding_i386(struct baton baton, uint8_t *function_start,
uint32_t encoding) {
int mode = encoding & UNWIND_X86_MODE_MASK;
switch (mode) {
case UNWIND_X86_MODE_EBP_FRAME: {
printf("frame func: CFA is ebp+%d ", 8);
printf(" eip=[CFA-4] ebp=[CFA-8]");
uint32_t saved_registers_offset =
EXTRACT_BITS(encoding, UNWIND_X86_EBP_FRAME_OFFSET);
uint32_t saved_registers_locations =
EXTRACT_BITS(encoding, UNWIND_X86_EBP_FRAME_REGISTERS);
saved_registers_offset += 2;
for (int i = 0; i < 5; i++) {
switch (saved_registers_locations & 0x7) {
case UNWIND_X86_REG_NONE:
break;
case UNWIND_X86_REG_EBX:
printf(" ebx=[CFA-%d]", saved_registers_offset * 4);
break;
case UNWIND_X86_REG_ECX:
printf(" ecx=[CFA-%d]", saved_registers_offset * 4);
break;
case UNWIND_X86_REG_EDX:
printf(" edx=[CFA-%d]", saved_registers_offset * 4);
break;
case UNWIND_X86_REG_EDI:
printf(" edi=[CFA-%d]", saved_registers_offset * 4);
break;
case UNWIND_X86_REG_ESI:
printf(" esi=[CFA-%d]", saved_registers_offset * 4);
break;
}
saved_registers_offset--;
saved_registers_locations >>= 3;
}
} break;
case UNWIND_X86_MODE_STACK_IND:
case UNWIND_X86_MODE_STACK_IMMD: {
uint32_t stack_size =
EXTRACT_BITS(encoding, UNWIND_X86_FRAMELESS_STACK_SIZE);
uint32_t register_count =
EXTRACT_BITS(encoding, UNWIND_X86_FRAMELESS_STACK_REG_COUNT);
uint32_t permutation =
EXTRACT_BITS(encoding, UNWIND_X86_FRAMELESS_STACK_REG_PERMUTATION);
if (mode == UNWIND_X86_MODE_STACK_IND && function_start) {
uint32_t stack_adjust =
EXTRACT_BITS(encoding, UNWIND_X86_FRAMELESS_STACK_ADJUST);
// offset into the function instructions; 0 == beginning of first
// instruction
uint32_t offset_to_subl_insn =
EXTRACT_BITS(encoding, UNWIND_X86_FRAMELESS_STACK_SIZE);
stack_size = *((uint32_t *)(function_start + offset_to_subl_insn));
stack_size += stack_adjust * 4;
printf("large stack ");
}
if (mode == UNWIND_X86_MODE_STACK_IND) {
printf("frameless function: stack size %d, register count %d ",
stack_size, register_count);
} else {
printf("frameless function: stack size %d, register count %d ",
stack_size * 4, register_count);
}
if (register_count == 0) {
printf(" no registers saved");
} else {
// We need to include (up to) 6 registers in 10 bits.
// That would be 18 bits if we just used 3 bits per reg to indicate
// the order they're saved on the stack.
//
// This is done with Lehmer code permutation, e.g. see
// http://stackoverflow.com/questions/1506078/fast-permutation-number-permutation-mapping-algorithms
int permunreg[6];
// This decodes the variable-base number in the 10 bits
// and gives us the Lehmer code sequence which can then
// be decoded.
switch (register_count) {
case 6:
permunreg[0] = permutation / 120; // 120 == 5!
permutation -= (permunreg[0] * 120);
permunreg[1] = permutation / 24; // 24 == 4!
permutation -= (permunreg[1] * 24);
permunreg[2] = permutation / 6; // 6 == 3!
permutation -= (permunreg[2] * 6);
permunreg[3] = permutation / 2; // 2 == 2!
permutation -= (permunreg[3] * 2);
permunreg[4] = permutation; // 1 == 1!
permunreg[5] = 0;
break;
case 5:
permunreg[0] = permutation / 120;
permutation -= (permunreg[0] * 120);
permunreg[1] = permutation / 24;
permutation -= (permunreg[1] * 24);
permunreg[2] = permutation / 6;
permutation -= (permunreg[2] * 6);
permunreg[3] = permutation / 2;
permutation -= (permunreg[3] * 2);
permunreg[4] = permutation;
break;
case 4:
permunreg[0] = permutation / 60;
permutation -= (permunreg[0] * 60);
permunreg[1] = permutation / 12;
permutation -= (permunreg[1] * 12);
permunreg[2] = permutation / 3;
permutation -= (permunreg[2] * 3);
permunreg[3] = permutation;
break;
case 3:
permunreg[0] = permutation / 20;
permutation -= (permunreg[0] * 20);
permunreg[1] = permutation / 4;
permutation -= (permunreg[1] * 4);
permunreg[2] = permutation;
break;
case 2:
permunreg[0] = permutation / 5;
permutation -= (permunreg[0] * 5);
permunreg[1] = permutation;
break;
case 1:
permunreg[0] = permutation;
break;
}
// Decode the Lehmer code for this permutation of
// the registers v. http://en.wikipedia.org/wiki/Lehmer_code
int registers[6];
bool used[7] = {false, false, false, false, false, false, false};
for (int i = 0; i < register_count; i++) {
int renum = 0;
for (int j = 1; j < 7; j++) {
if (used[j] == false) {
if (renum == permunreg[i]) {
registers[i] = j;
used[j] = true;
break;
}
renum++;
}
}
}
if (mode == UNWIND_X86_MODE_STACK_IND) {
printf(" CFA is esp+%d ", stack_size);
} else {
printf(" CFA is esp+%d ", stack_size * 4);
}
uint32_t saved_registers_offset = 1;
printf(" eip=[CFA-%d]", saved_registers_offset * 4);
saved_registers_offset++;
for (int i = (sizeof(registers) / sizeof(int)) - 1; i >= 0; i--) {
switch (registers[i]) {
case UNWIND_X86_REG_NONE:
break;
case UNWIND_X86_REG_EBX:
printf(" ebx=[CFA-%d]", saved_registers_offset * 4);
saved_registers_offset++;
break;
case UNWIND_X86_REG_ECX:
printf(" ecx=[CFA-%d]", saved_registers_offset * 4);
saved_registers_offset++;
break;
case UNWIND_X86_REG_EDX:
printf(" edx=[CFA-%d]", saved_registers_offset * 4);
saved_registers_offset++;
break;
case UNWIND_X86_REG_EDI:
printf(" edi=[CFA-%d]", saved_registers_offset * 4);
saved_registers_offset++;
break;
case UNWIND_X86_REG_ESI:
printf(" esi=[CFA-%d]", saved_registers_offset * 4);
saved_registers_offset++;
break;
case UNWIND_X86_REG_EBP:
printf(" ebp=[CFA-%d]", saved_registers_offset * 4);
saved_registers_offset++;
break;
}
}
}
} break;
case UNWIND_X86_MODE_DWARF: {
uint32_t dwarf_offset = encoding & UNWIND_X86_DWARF_SECTION_OFFSET;
printf(
"DWARF unwind instructions: FDE at offset %d (file address 0x%" PRIx64
")",
dwarf_offset, dwarf_offset + baton.eh_section_file_address);
} break;
case 0: {
printf(" no unwind information");
} break;
}
}
void print_encoding_arm64(struct baton baton, uint8_t *function_start,
uint32_t encoding) {
const int wordsize = 8;
int mode = encoding & UNWIND_ARM64_MODE_MASK;
switch (mode) {
case UNWIND_ARM64_MODE_FRAME: {
printf("frame func: CFA is fp+%d ", 16);
printf(" pc=[CFA-8] fp=[CFA-16]");
int reg_pairs_saved_count = 1;
uint32_t saved_register_bits = encoding & 0xfff;
if (saved_register_bits & UNWIND_ARM64_FRAME_X19_X20_PAIR) {
int cfa_offset = reg_pairs_saved_count * -2 * wordsize;
cfa_offset -= wordsize;
printf(" x19=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" x20=[CFA%d]", cfa_offset);
reg_pairs_saved_count++;
}
if (saved_register_bits & UNWIND_ARM64_FRAME_X21_X22_PAIR) {
int cfa_offset = reg_pairs_saved_count * -2 * wordsize;
cfa_offset -= wordsize;
printf(" x21=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" x22=[CFA%d]", cfa_offset);
reg_pairs_saved_count++;
}
if (saved_register_bits & UNWIND_ARM64_FRAME_X23_X24_PAIR) {
int cfa_offset = reg_pairs_saved_count * -2 * wordsize;
cfa_offset -= wordsize;
printf(" x23=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" x24=[CFA%d]", cfa_offset);
reg_pairs_saved_count++;
}
if (saved_register_bits & UNWIND_ARM64_FRAME_X25_X26_PAIR) {
int cfa_offset = reg_pairs_saved_count * -2 * wordsize;
cfa_offset -= wordsize;
printf(" x25=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" x26=[CFA%d]", cfa_offset);
reg_pairs_saved_count++;
}
if (saved_register_bits & UNWIND_ARM64_FRAME_X27_X28_PAIR) {
int cfa_offset = reg_pairs_saved_count * -2 * wordsize;
cfa_offset -= wordsize;
printf(" x27=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" x28=[CFA%d]", cfa_offset);
reg_pairs_saved_count++;
}
if (saved_register_bits & UNWIND_ARM64_FRAME_D8_D9_PAIR) {
int cfa_offset = reg_pairs_saved_count * -2 * wordsize;
cfa_offset -= wordsize;
printf(" d8=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" d9=[CFA%d]", cfa_offset);
reg_pairs_saved_count++;
}
if (saved_register_bits & UNWIND_ARM64_FRAME_D10_D11_PAIR) {
int cfa_offset = reg_pairs_saved_count * -2 * wordsize;
cfa_offset -= wordsize;
printf(" d10=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" d11=[CFA%d]", cfa_offset);
reg_pairs_saved_count++;
}
if (saved_register_bits & UNWIND_ARM64_FRAME_D12_D13_PAIR) {
int cfa_offset = reg_pairs_saved_count * -2 * wordsize;
cfa_offset -= wordsize;
printf(" d12=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" d13=[CFA%d]", cfa_offset);
reg_pairs_saved_count++;
}
if (saved_register_bits & UNWIND_ARM64_FRAME_D14_D15_PAIR) {
int cfa_offset = reg_pairs_saved_count * -2 * wordsize;
cfa_offset -= wordsize;
printf(" d14=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" d15=[CFA%d]", cfa_offset);
reg_pairs_saved_count++;
}
} break;
case UNWIND_ARM64_MODE_FRAMELESS: {
uint32_t stack_size = encoding & UNWIND_ARM64_FRAMELESS_STACK_SIZE_MASK;
printf("frameless function: stack size %d ", stack_size * 16);
} break;
case UNWIND_ARM64_MODE_DWARF: {
uint32_t dwarf_offset = encoding & UNWIND_ARM64_DWARF_SECTION_OFFSET;
printf(
"DWARF unwind instructions: FDE at offset %d (file address 0x%" PRIx64
")",
dwarf_offset, dwarf_offset + baton.eh_section_file_address);
} break;
case 0: {
printf(" no unwind information");
} break;
}
}
void print_encoding_armv7(struct baton baton, uint8_t *function_start,
uint32_t encoding) {
const int wordsize = 4;
int mode = encoding & UNWIND_ARM_MODE_MASK;
switch (mode) {
case UNWIND_ARM_MODE_FRAME_D:
case UNWIND_ARM_MODE_FRAME: {
int stack_adjust =
EXTRACT_BITS(encoding, UNWIND_ARM_FRAME_STACK_ADJUST_MASK) * wordsize;
printf("frame func: CFA is fp+%d ", (2 * wordsize) + stack_adjust);
int cfa_offset = -stack_adjust;
cfa_offset -= wordsize;
printf(" pc=[CFA%d]", cfa_offset);
cfa_offset -= wordsize;
printf(" fp=[CFA%d]", cfa_offset);
uint32_t saved_register_bits = encoding & 0xff;
if (saved_register_bits & UNWIND_ARM_FRAME_FIRST_PUSH_R6) {
cfa_offset -= wordsize;
printf(" r6=[CFA%d]", cfa_offset);
}
if (saved_register_bits & UNWIND_ARM_FRAME_FIRST_PUSH_R5) {
cfa_offset -= wordsize;
printf(" r5=[CFA%d]", cfa_offset);
}
if (saved_register_bits & UNWIND_ARM_FRAME_FIRST_PUSH_R4) {
cfa_offset -= wordsize;
printf(" r4=[CFA%d]", cfa_offset);
}
if (saved_register_bits & UNWIND_ARM_FRAME_SECOND_PUSH_R12) {
cfa_offset -= wordsize;
printf(" r12=[CFA%d]", cfa_offset);
}
if (saved_register_bits & UNWIND_ARM_FRAME_SECOND_PUSH_R11) {
cfa_offset -= wordsize;