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[init] Randomize load address of dynamic ELF modules

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Update init to use the new xoroshiro RNG to create a random load address for dynamic executables.
Also pass an address past the end of the loader in the loader_arg to use when loading dynamic
dependencies.
This commit is contained in:
Justin C. Miller
2024-02-19 15:00:42 -08:00
parent 0bf709a339
commit dff9e53658
3 changed files with 12 additions and 4 deletions
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11
src/user/srv.init/loader.cpp
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@@ -10,6 +10,7 @@
#include <j6/protocols.h>
#include <j6/syscalls.h>
#include <j6/syslog.hh>
#include <util/xoroshiro.h>
#include "j6romfs.h"
#include "loader.h"
@@ -20,6 +21,8 @@ static constexpr size_t MiB = 0x10'0000ull;
static constexpr size_t stack_size = 16 * MiB;
static constexpr uintptr_t stack_top = 0x7f0'0000'0000;
static util::xoroshiro256pp rng {0x123456};
inline uintptr_t align_up(uintptr_t a) { return ((a-1) & ~(MiB-1)) + MiB; }
j6_handle_t
@@ -180,7 +183,9 @@ load_program(
elf::file program_elf {program_data};
bool dyn = program_elf.type() == elf::filetype::shared;
uintptr_t program_image_base = dyn ? 0xa00'0000 : 0;
uintptr_t program_image_base = 0;
if (dyn)
program_image_base = (rng.next() & 0xffe0 + 16) << 20;
if (!program_elf.valid(dyn ? elf::filetype::shared : elf::filetype::executable)) {
j6::syslog(" ** error loading program '%s': ELF is invalid", path);
@@ -250,8 +255,10 @@ load_program(
return false;
}
load_program_into(proc, ldso_elf, ldso_image_base, ldso_path);
uintptr_t eop = load_program_into(proc, ldso_elf, ldso_image_base, ldso_path);
eop = (eop & ~0xfffffull) + 0x100000;
loader_arg->loader_base = ldso_image_base;
loader_arg->start_addr = eop;
entrypoint = ldso_elf.entrypoint() + ldso_image_base;
delete [] reinterpret_cast<uint8_t*>(ldso_data.pointer);
break;