diff options
Diffstat (limited to '04_dynld_nostd/dynld.c')
| -rw-r--r-- | 04_dynld_nostd/dynld.c | 41 |
1 files changed, 17 insertions, 24 deletions
diff --git a/04_dynld_nostd/dynld.c b/04_dynld_nostd/dynld.c index 9b14590..02fbe9e 100644 --- a/04_dynld_nostd/dynld.c +++ b/04_dynld_nostd/dynld.c @@ -34,7 +34,7 @@ typedef struct { // Interpret and extract data passed on the stack by the Linux Kernel // when loading the initial process image. // The data is organized according to the SystemV x86_64 ABI. -ExecInfo get_exec_info(const uint64_t* prctx) { +static ExecInfo get_exec_info(const uint64_t* prctx) { ExecInfo info = {0}; info.argc = *prctx; @@ -64,10 +64,10 @@ typedef struct { void (*entry)(); // Entry function. uint64_t dynamic[DT_MAX_CNT]; // `.dynamic` section entries. uint64_t needed[MAX_NEEDED]; // Shared object dependencies (`DT_NEEDED` entries). - uint8_t needed_len; // Number of `DT_NEEDED` entries (SO dependencies). + uint32_t needed_len; // Number of `DT_NEEDED` entries (SO dependencies). } Dso; -void decode_dynamic(Dso* dso, uint64_t dynoff) { +static void decode_dynamic(Dso* dso, uint64_t dynoff) { // Decode `.dynamic` section of the `dso`. for (const Elf64Dyn* dyn = (const Elf64Dyn*)(dso->base + dynoff); dyn->tag != DT_NULL; ++dyn) { if (dyn->tag == DT_NEEDED) { @@ -87,18 +87,12 @@ void decode_dynamic(Dso* dso, uint64_t dynoff) { ERROR_ON(dso->dynamic[DT_SYMENT] == 0, "DT_SYMENT missing in dynamic section!"); ERROR_ON(dso->dynamic[DT_SYMENT] != sizeof(Elf64Sym), "ELf64Sym size miss-match!"); - // Check for relocation entries related to PLT. - // ERROR_ON(dso->dynamic[DT_JMPREL] == 0, "DT_JMPREL missing in dynamic section!"); - // ERROR_ON(dso->dynamic[DT_PLTRELSZ] == 0, "DT_PLTRELSZ missing in dynamic section!"); - // ERROR_ON(dso->dynamic[DT_PLTREL] == 0, "DT_PLTREL missing in dynamic section!"); - // ERROR_ON(dso->dynamic[DT_PLTREL] != DT_RELA, "x86_64 only uses RELA entries!"); - // Check for SystemV hash table. We only support SystemV hash tables // `DT_HASH`, not gnu hash tables `DT_GNU_HASH`. ERROR_ON(dso->dynamic[DT_HASH] == 0, "DT_HASH missing in dynamic section!"); } -Dso get_prog_dso(const ExecInfo* info) { +static Dso get_prog_dso(const ExecInfo* info) { Dso prog = {0}; // Determine the base address of the user program. @@ -158,7 +152,7 @@ Dso get_prog_dso(const ExecInfo* info) { return prog; } -uint64_t get_num_dynsyms(const Dso* dso) { +static uint64_t get_num_dynsyms(const Dso* dso) { ERROR_ON(dso->dynamic[DT_HASH] == 0, "DT_HASH missing in dynamic section!"); // Get SystemV hash table. @@ -177,22 +171,22 @@ uint64_t get_num_dynsyms(const Dso* dso) { return hashtab[1]; } -const char* get_str(const Dso* dso, const uint64_t idx) { +static const char* get_str(const Dso* dso, uint64_t idx) { ERROR_ON(dso->dynamic[DT_STRSZ] < idx, "String table indexed out-of-bounds!"); return (const char*)(dso->base + dso->dynamic[DT_STRTAB] + idx); } -const Elf64Sym* get_sym(const Dso* dso, const uint64_t idx) { +static const Elf64Sym* get_sym(const Dso* dso, uint64_t idx) { ERROR_ON(get_num_dynsyms(dso) < idx, "Symbol table index out-of-bounds!"); return (const Elf64Sym*)(dso->base + dso->dynamic[DT_SYMTAB]) + idx; } -const Elf64Rela* get_pltreloca(const Dso* dso, const uint64_t idx) { +static const Elf64Rela* get_pltreloca(const Dso* dso, uint64_t idx) { ERROR_ON(dso->dynamic[DT_PLTRELSZ] < sizeof(Elf64Rela) * idx, "PLT relocation table indexed out-of-bounds!"); return (const Elf64Rela*)(dso->base + dso->dynamic[DT_JMPREL]) + idx; } -const Elf64Rela* get_reloca(const Dso* dso, const uint64_t idx) { +static const Elf64Rela* get_reloca(const Dso* dso, uint64_t idx) { ERROR_ON(dso->dynamic[DT_RELASZ] < sizeof(Elf64Rela) * idx, "RELA relocation table indexed out-of-bounds!"); return (const Elf64Rela*)(dso->base + dso->dynamic[DT_RELA]) + idx; } @@ -233,7 +227,7 @@ static void fini(const Dso* dso) { // }}} // {{{ Symbol lookup -int strcmp(const char* s1, const char* s2) { +static inline int strcmp(const char* s1, const char* s2) { while (*s1 == *s2 && *s1) { ++s1; ++s2; @@ -249,14 +243,14 @@ int strcmp(const char* s1, const char* s2) { // performance for large symbol tables. // // `dso` A handle to the dso which dynamic symbol table should be searched. -// `sym_name` Name of the symbol to look up. -void* lookup_sym(const Dso* dso, const char* sym_name) { +// `symname` Name of the symbol to look up. +static void* lookup_sym(const Dso* dso, const char* symname) { for (unsigned i = 0; i < get_num_dynsyms(dso); ++i) { const Elf64Sym* sym = get_sym(dso, i); if ((ELF64_ST_TYPE(sym->info) == STT_OBJECT || ELF64_ST_TYPE(sym->info) == STT_FUNC) && ELF64_ST_BIND(sym->info) == STB_GLOBAL && sym->shndx != SHN_UNDEF) { - if (strcmp(sym_name, get_str(dso, sym->name)) == 0) { + if (strcmp(symname, get_str(dso, sym->name)) == 0) { return dso->base + sym->value; } } @@ -267,7 +261,7 @@ void* lookup_sym(const Dso* dso, const char* sym_name) { // }}} // {{{ Map Shared Library Dependency -Dso map_dependency(const char* dependency) { +static Dso map_dependency(const char* dependency) { // For simplicity we only search for SO dependencies in the current working dir. ERROR_ON(access(dependency, R_OK) != 0, "Dependency '%s' does not exist!\n", dependency); @@ -376,11 +370,10 @@ Dso map_dependency(const char* dependency) { // }}} // {{{ Resolve relocations -struct LinkMap { +typedef struct LinkMap { const Dso* dso; // Pointer to Dso list object. const struct LinkMap* next; // Pointer to next LinkMap entry ('0' terminates the list). -}; -typedef struct LinkMap LinkMap; +} LinkMap; // Resolve a single relocation of `dso`. // @@ -482,7 +475,7 @@ __attribute__((used)) __attribute__((unused)) static void dynresolve(uint64_t go // }}} // {{{ Setup GOT -void setup_got(const Dso* dso) { +static void setup_got(const Dso* dso) { // GOT entries {0, 1, 2} have special meaning for the dynamic link process. // GOT[0] Hold address of dynamic structure referenced by `_DYNAMIC`. // GOT[1] Argument pushed by PLT0 pad on stack before jumping to GOT[2], |