YJN/selfpatch-slr
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Finalizer__spslr_program pointer patch

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This commit is contained in:
York Jasper Niebuhr 2025-10-27 23:06:23 +01:00
parent 9c1769549c
commit 527db5ce1f
2 changed files with 28 additions and 8 deletions
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21
finalize/finalize.cpp
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@ -178,7 +178,26 @@ int main(int argc, char** argv) {
bin->add(new_seg);
// Set __spslr_program to (new_vaddr - &__spslr_program)
// TODO
for (Segment& seg : bin->segments()) {
uint64_t start = seg.virtual_address();
uint64_t end_mem = start + seg.virtual_size();
if (spslr_program_ptr_address >= start && spslr_program_ptr_address < end_mem) {
uint64_t offset_within_seg = spslr_program_ptr_address - start;
uint64_t min_needed = offset_within_seg + sizeof(uint64_t);
if (min_needed > seg.physical_size())
seg.physical_size(min_needed);
break;
}
}
uint64_t relative_new_vaddr = new_vaddr - spslr_program_ptr_address;
std::vector<uint8_t> program_ptr_bytes;
program_ptr_bytes.resize(8);
std::memcpy(program_ptr_bytes.data(), &relative_new_vaddr, 8);
bin->patch_address(spslr_program_ptr_address, program_ptr_bytes);
// Output final program
Builder builder{ *bin };

15
selfpatch/src/selfpatch.c
View File

@ -6,13 +6,6 @@
#include "targets.h"
#include "patcher.h"
/*
TODO
Postprocessing tool patches the value of __spslr_program to point to the SPSLR program section.
With ASLR, there are 2 options to make it function correctly:
1. Make sure __spslr_program is relocated with program image shift (preferred)
2. __spslr_program = spslr_ptr_absolute((uint64_t)__spslr_program) and postprocessor inserts relative value (kinda weird)
*/
const uint8_t* __spslr_program = NULL;
static void* spslr_ptr_absolute(uint64_t relative) {
@ -20,6 +13,12 @@ static void* spslr_ptr_absolute(uint64_t relative) {
return ((uint8_t*)&__spslr_program) + relative;
}
static void spslr_init_program_ptr() {
// Finalizer patches __spslr_program to be the relative offset from &__spslr_program to the program
uint64_t relative = (uint64_t)__spslr_program;
__spslr_program = (const uint8_t*)spslr_ptr_absolute(relative);
}
static int spslr_do(const struct SPSLR_INST* inst) {
if (!inst)
return -1;
@ -65,6 +64,8 @@ void spslr_selfpatch() {
return;
}
spslr_init_program_ptr();
int sz;
struct SPSLR_INST inst;
while ((sz = spslr_inst_load(&inst, __spslr_program)) > 0) {