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Handle detour patches across page boundaries (#1535)

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On Linux if a detour crossed a page boundary we would only change the
memory protection of the first page (as we were aligning the address as
required, but not taking into account the length).

I don't have an easy way to test this but it looks correct. `addr + len`
doesn't appear to need to be aligned though, so another option could be
to use `(addr - startPage) + length` as len.

Also fixed a non-zero offset being passed into CDetour's ApplyPatch
function - this is never done internally anywhere, but it doesn't hurt
to fix it.

Fixes #984
This commit is contained in:
Asher Baker 2021-07-17 20:53:25 +01:00 committed by GitHub
parent 7f2fdf3fe1
commit 5b7c9c5845
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1 changed files with 7 additions and 8 deletions
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15
public/CDetour/detourhelpers.h
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@ -34,13 +34,10 @@
#if defined PLATFORM_POSIX
#include <sys/mman.h>
#ifndef PAGE_SIZE
#define PAGE_SIZE 4096
#endif
#define ALIGN(ar) ((long)ar & ~(PAGE_SIZE-1))
#define PAGE_EXECUTE_READWRITE PROT_READ|PROT_WRITE|PROT_EXEC
#endif
#include <amtl/am-bits.h>
#include <jit/x86/x86_macros.h>
struct patch_t
@ -57,8 +54,10 @@ struct patch_t
inline void ProtectMemory(void *addr, int length, int prot)
{
#if defined PLATFORM_POSIX
void *addr2 = (void *)ALIGN(addr);
mprotect(addr2, sysconf(_SC_PAGESIZE), prot);
long pageSize = sysconf(_SC_PAGESIZE);
void *startPage = ke::AlignedBase(addr, pageSize);
void *endPage = ke::AlignedBase((void *)((intptr_t)addr + length), pageSize);
mprotect(startPage, ((intptr_t)endPage - (intptr_t)startPage) + pageSize, prot);
#elif defined PLATFORM_WINDOWS
DWORD old_prot;
VirtualProtect(addr, length, prot, &old_prot);
@ -118,9 +117,9 @@ inline void DoGatePatch(unsigned char *target, void *callback)
inline void ApplyPatch(void *address, int offset, const patch_t *patch, patch_t *restore)
{
ProtectMemory(address, 20, PAGE_EXECUTE_READWRITE);
unsigned char *addr = (unsigned char *)address + offset;
SetMemPatchable(addr, patch->bytes);
if (restore)
{
for (size_t i=0; i<patch->bytes; i++)