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remove the symbol-table walking

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it wasn't feasible without knowledge of the size which I couldn't find without reading the elf file. Moreover, it wasn't really required and was halting progress
This commit is contained in:
Kasper
2025-03-23 01:39:34 +02:00
parent 36ca3a2155
commit 564d2490e5
4 changed files with 13 additions and 121 deletions
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22
src/hiload.c
View File

@@ -43,7 +43,8 @@ static inline int if_load_symbols_for_module(struct dl_phdr_info *info) {
}
// Callback function for dl_iterate_phdr
static int gather_module_infos_callback(struct dl_phdr_info *info, size_t size,
static
int gather_module_infos_callback(struct dl_phdr_info *info, size_t size,
void *data) {
ModuleInfos *infos = (ModuleInfos *)data;
@@ -68,20 +69,11 @@ static int gather_module_infos_callback(struct dl_phdr_info *info, size_t size,
SymbolInfos symbol_info = {0};
sc_array_add(&infos->symbols, symbol_info);
if (!if_load_symbols_for_module(info)) {
sc_log_info("Skipping symbol preload for: %s\n", info->dlpi_name);
return 0;
}
if (hi_create_symbol_info(&(sc_array_last(&infos->symbols)),
&context.memory_regions, info) != HILOAD_OK) {
sc_log_error("Failed to create symbol info for %s\n", info->dlpi_name);
}
return 0; // Continue iteration
}
static void free_module_infos(ModuleInfos *modules) {
static
void free_module_infos(ModuleInfos *modules) {
if (!modules)
return;
@@ -101,7 +93,8 @@ static void free_module_infos(ModuleInfos *modules) {
free(modules);
}
static ModuleInfos *gather_module_infos(void) {
static
ModuleInfos *gather_module_infos(void) {
ModuleInfos *result = NULL;
// Allocate the result structure
@@ -120,7 +113,8 @@ static ModuleInfos *gather_module_infos(void) {
return result;
}
static ReloadResult reload_module(ModuleInfos *modules, const char *filename,
static
ReloadResult reload_module(ModuleInfos *modules, const char *filename,
void **updated_handle) {
if (!modules || !filename) {
return HI_RELOAD_NOT_FOUND;

102
src/symbols.c
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@@ -4,13 +4,7 @@
#include "memory.h"
#include "types.h"
#include <dlfcn.h>
#include <elf.h>
#include <link.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static inline uptr
add_ptr_offset_if_invalid(uptr p, uptr offset,
@@ -20,102 +14,6 @@ add_ptr_offset_if_invalid(uptr p, uptr offset,
return p;
}
/**
* Gathers and populates symbols, given a dynamic module info
*/
HiloadResult hi_create_symbol_info(SymbolInfos *symbols,
struct sc_array_memreg *const regions,
struct dl_phdr_info *info) {
if (!symbols)
return HILOAD_FAIL;
hi_free_symbol_info(symbols);
for (int i = 0; i < info->dlpi_phnum; i++) {
const ElfW(Phdr) *phdr = &info->dlpi_phdr[i];
}
for (int i = 0; i < info->dlpi_phnum; i++) {
const ElfW(Phdr) *phdr = &info->dlpi_phdr[i];
// Look for the dynamic segment
if (phdr->p_type != PT_DYNAMIC)
continue;
sc_log_debug("Dynamic Header:\n");
sc_log_debug("p_type: %u\n", phdr->p_type);
sc_log_debug("p_flags: %u\n", phdr->p_flags);
sc_log_debug("p_offset: %#06lx\n", phdr->p_offset);
sc_log_debug("p_vaddr: %#06lx\n", phdr->p_vaddr);
sc_log_debug("p_paddr: %#06lx\n", phdr->p_paddr);
sc_log_debug("p_filesz: %zu\n", phdr->p_filesz);
sc_log_debug("p_memsz: %zu\n", phdr->p_memsz);
sc_log_debug("p_align: %zu\n", phdr->p_align);
const ElfW(Dyn) *dyn = (const ElfW(Dyn) *)(info->dlpi_addr + phdr->p_vaddr);
const char *strtab = NULL;
const ElfW(Sym) *symtab = NULL;
size_t strtab_size = 0;
uptr off = info->dlpi_addr;
// Parse the dynamic table. Add offset if address is not in executable
// memory. NOTE: Haven't found a better way to differentiate with items that
// have relative address, and items that don't.
for (; dyn->d_tag != DT_NULL; dyn++) {
if (dyn->d_tag == DT_STRTAB) {
uptr p = dyn->d_un.d_ptr;
p = add_ptr_offset_if_invalid(p, off, regions);
strtab = (const char *)p;
} else if (dyn->d_tag == DT_STRSZ) {
strtab_size = dyn->d_un.d_val;
} else if (dyn->d_tag == DT_SYMTAB) {
uptr p = dyn->d_un.d_ptr;
p = add_ptr_offset_if_invalid(p, off, regions);
symtab = (const ElfW(Sym) *)(p);
}
}
// Ensure we found the symbol and string tables
if (!strtab || !symtab || strtab_size == 0) {
sc_log_error("Failed to find symbol or string table in %s\n",
info->dlpi_name);
return HILOAD_FAIL;
}
// Iterate over the symbol table
// We assume the dynsym and dynstr are linked
const char *strptr = strtab;
for (const ElfW(Sym) *sym = symtab;; sym++) {
// escape if we'd hit the end of string table
strptr = strtab + sym->st_name;
if (strptr + strlen(strptr) + 1 >= strtab + strtab_size)
break;
if (ELF64_ST_TYPE(sym->st_info) == STT_FUNC ||
ELF64_ST_TYPE(sym->st_info) == STT_OBJECT) {
const char *name = strdup(strtab + sym->st_name);
void *address = (void *)(info->dlpi_addr + sym->st_value);
// Store the symbol information in the arrays
sc_array_add(&symbols->names, name);
sc_array_add(&symbols->addresses, address);
sc_log_debug("%s: %p\n", name, address);
}
}
}
sc_log_debug("Symbols for %s gathered...\n", info->dlpi_name);
return HILOAD_OK;
}
void hi_free_symbol_info(SymbolInfos *symbols) {
for (size_t i = 0; i < symbols->names.size; i++) {
free((void *)symbols->names.elems[i]);

5
src/symbols.h
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@@ -15,11 +15,6 @@ typedef struct {
sc_array_def(SymbolInfos, syms);
struct dl_phdr_info;
struct sc_array_memreg;
HiloadResult hi_create_symbol_info(SymbolInfos *,
struct sc_array_memreg *const regions,
struct dl_phdr_info *);
void hi_free_symbol_info(SymbolInfos *);
#endif // SYMBOLS_H_

5
test/manual/CMakeLists.txt
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@@ -1,6 +1,11 @@
project(Minimal)
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
set(CMAKE_BUILD_TYPE "Debug")
add_compile_options(-g -ffunction-sections -fdata-sections)
add_executable(minimal
minimal.cpp
)