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Rework BCeNabler memory permissions for ---X

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This commit is contained in:
Billy Laws 2022-01-13 18:22:47 +00:00
parent 526ed96751
commit 4820e60412
1 changed files with 28 additions and 19 deletions
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43
src/bcenabler.cpp
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@ -37,6 +37,10 @@ static void *find_free_page(uintptr_t address) {
return nullptr;
}
static void *align_ptr(void *ptr) {
return reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(ptr) & ~(PAGE_SIZE - 1));
}
bool adrenotools_patch_bcn(void *vkGetPhysicalDeviceFormatPropertiesFn) {
union Branch {
struct {
@ -48,6 +52,21 @@ bool adrenotools_patch_bcn(void *vkGetPhysicalDeviceFormatPropertiesFn) {
};
static_assert(sizeof(Branch) == 4, "Branch size is invalid");
// Find the nearest unmapped page where we can place patch code
void *patchPage{find_free_page(reinterpret_cast<uintptr_t>(vkGetPhysicalDeviceFormatPropertiesFn))};
if (!patchPage)
return false;
// Map patch region
void *ptr{mmap(patchPage, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, 0, 0)};
if (ptr != patchPage)
return false;
// Allow reading from the blob's .text section since some devices enable ---X
// Protect two pages just in case we happen to land on a page boundary
if (mprotect(align_ptr(vkGetPhysicalDeviceFormatPropertiesFn), PAGE_SIZE * 2, PROT_WRITE | PROT_READ | PROT_EXEC))
return false;
// First branch in this function is targeted at the function we want to patch
Branch *blInst{reinterpret_cast<Branch *>(vkGetPhysicalDeviceFormatPropertiesFn)};
@ -60,6 +79,11 @@ bool adrenotools_patch_bcn(void *vkGetPhysicalDeviceFormatPropertiesFn) {
// Internal QGL format conversion function that we need to patch
uint32_t *convFormatFn{reinterpret_cast<uint32_t *>(blInst) + blInst->offset};
// See mprotect call above
// This time we also set PROT_WRITE so we can write our patch to the page
if (mprotect(align_ptr(convFormatFn), PAGE_SIZE * 2, PROT_WRITE | PROT_READ | PROT_EXEC))
return false;
// This would normally set the default result to 0 (error) in the format not found case
constexpr uint32_t ClearResultSignature{0x2a1f03e0};
@ -68,15 +92,6 @@ bool adrenotools_patch_bcn(void *vkGetPhysicalDeviceFormatPropertiesFn) {
while (*clearResultPtr != ClearResultSignature)
clearResultPtr++;
// Find the nearest unmapped page where we can place patch code
void *patchPage{find_free_page(reinterpret_cast<uintptr_t>(clearResultPtr))};
if (!patchPage)
return false;
void *ptr{mmap(patchPage, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, 0, 0)};
if (ptr != patchPage)
return false;
// Ensure we don't write out of bounds
if (PatchRawData_size > PAGE_SIZE)
return false;
@ -88,8 +103,8 @@ bool adrenotools_patch_bcn(void *vkGetPhysicalDeviceFormatPropertiesFn) {
constexpr uint32_t PatchReturnFixupMagic{0xffffffff};
constexpr uint8_t BranchSignature{0x5};
uint32_t *fixupTargetPtr = clearResultPtr + 1;
uint32_t *fixupPtr = reinterpret_cast<uint32_t *>(patchPage);
uint32_t *fixupTargetPtr{clearResultPtr + 1};
auto *fixupPtr{reinterpret_cast<uint32_t *>(patchPage)};
for (long unsigned int i{}; i < (PatchRawData_size / sizeof(uint32_t)); i++, fixupPtr++) {
if (*fixupPtr == PatchReturnFixupMagic) {
Branch branchToDriver{
@ -110,12 +125,6 @@ bool adrenotools_patch_bcn(void *vkGetPhysicalDeviceFormatPropertiesFn) {
}
};
void *driverPatchPage{reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(clearResultPtr) & ~(PAGE_SIZE - 1))};
// For some reason mprotect just breaks entirely after we patch the QGL instruction so just set perms to RWX
if (mprotect(driverPatchPage, PAGE_SIZE, PROT_WRITE | PROT_READ | PROT_EXEC))
return false;
*clearResultPtr = branchToPatch.raw;
asm volatile("ISB");