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[TSan] Improve handling of stack pointer mangling in {set,long}jmp, pt.9 

Switch over to computing the xor key in C, instead of assembly for
Linux/AArch64.

llvm-svn: 366126
This commit is contained in:
Julian Lettner 2019-07-15 20:22:27 +00:00
parent 66ee934440
commit 39d888c1e4
1 changed files with 5 additions and 22 deletions
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27
compiler-rt/lib/tsan/rtl/tsan_platform_linux.cc
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@ -302,26 +302,8 @@ void InitializePlatform() {
CHECK_NE(personality(old_personality | ADDR_NO_RANDOMIZE), -1);
reexec = true;
}
// Initialize the guard pointer used in {sig}{set,long}jump.
longjmp_xor_key = InitializeGuardPtr();
// uptr old_value = longjmp_xor_key;
// InitializeLongjmpXorKey();
// CHECK_EQ(longjmp_xor_key, old_value);
// If the above check fails for you, please contact me (jlettner@apple.com)
// and let me know the values of the two differing keys. Please also set a
// breakpoint on `InitializeGuardPtr` and `InitializeLongjmpXorKey` and tell
// me the stack pointer (SP) values that go into the XOR operation (where we
// derive the key):
//
// InitializeLongjmpXorKey:
// uptr sp = (uptr)__builtin_frame_address(0);
//
// InitializeGuardPtr (in tsan_rtl_aarch64.S):
// mov x0, sp
// ...
// eor x0, x0, x1
//
// Then feel free to comment out the call to `InitializeLongjmpXorKey`.
// Initialize the xor key used in {sig}{set,long}jump.
InitializeLongjmpXorKey();
#endif
if (reexec)
ReExec();
@ -437,9 +419,10 @@ static void InitializeLongjmpXorKey() {
jmp_buf env;
REAL(_setjmp)(env);
// 2. Retrieve mangled/vanilla SP.
// 2. Retrieve vanilla/mangled SP.
uptr sp;
asm("mov %0, %%sp" : "=r" (sp));
uptr mangled_sp = ((uptr *)&env)[LONG_JMP_SP_ENV_SLOT];
uptr sp = (uptr)__builtin_frame_address(0);
// 3. xor SPs to obtain key.
longjmp_xor_key = mangled_sp ^ sp;