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DynamicLoader/LibC: lazy malloc environ

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This allows DynamicLoader to just set the value of global environ symbol
without libc needing to malloc it at startup
This commit is contained in:
Bananymous
2025-04-15 22:16:02 +03:00
parent 3721dadd72
commit 4f49d60e4a
3 changed files with 52 additions and 50 deletions
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34
userspace/programs/DynamicLoader/main.cpp
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@@ -857,16 +857,27 @@ static LoadedElf& load_elf(const char* path, int fd)
return elf;
}
static void call_init_libc(LoadedElf& elf, char** envp)
static void initialize_environ(char** envp)
{
const auto* _init_libc = find_symbol(elf, "_init_libc");
if (_init_libc == nullptr)
uintptr_t environ = SYM_NOT_FOUND;
for (size_t i = 0; i < s_loaded_file_count; i++)
{
const auto* match = find_symbol(s_loaded_files[i], "environ");
if (match == nullptr)
continue;
if (environ == SYM_NOT_FOUND || ELF_ST_BIND(match->st_info) != STB_WEAK)
environ = s_loaded_files[i].base + match->st_value;
if (ELF_ST_BIND(match->st_info) != STB_WEAK)
break;
}
if (environ == SYM_NOT_FOUND)
return;
using _init_libc_t = void(*)(char**);
reinterpret_cast<_init_libc_t>(elf.base + _init_libc->st_value)(envp);
*reinterpret_cast<char***>(environ) = envp;
}
static void call_init_funcs(LoadedElf& elf, char** envp, bool skip)
static void call_init_funcs(LoadedElf& elf, bool is_main_elf)
{
if (elf.has_called_init)
return;
@@ -879,11 +890,12 @@ static void call_init_funcs(LoadedElf& elf, char** envp, bool skip)
if (dynamic.d_tag == DT_NULL)
break;
if (dynamic.d_tag == DT_NEEDED)
call_init_funcs(*reinterpret_cast<LoadedElf*>(dynamic.d_un.d_ptr), envp, false);
call_init_funcs(*reinterpret_cast<LoadedElf*>(dynamic.d_un.d_ptr), false);
}
}
if (elf.has_called_init || skip)
// main executable calls its init functions in _start
if (elf.has_called_init || is_main_elf)
return;
using init_t = void(*)();
@@ -892,10 +904,7 @@ static void call_init_funcs(LoadedElf& elf, char** envp, bool skip)
for (size_t i = 0; i < elf.init_arraysz / sizeof(init_t); i++)
reinterpret_cast<init_t*>(elf.init_array)[i]();
if (strcmp(elf.path, "/usr/lib/libc.so") == 0)
call_init_libc(elf, envp);
elf.has_called_init = true;
}
extern "C"
@@ -922,6 +931,7 @@ int _entry(int argc, char** argv, char** envp, int fd)
fini_random();
relocate_elf(elf, true);
call_init_funcs(elf, envp, true);
initialize_environ(envp);
call_init_funcs(elf, true);
call_entry_point(argc, argv, envp, elf.base + elf.file_header.e_entry);
}