[libc-commits] [libc] [libc] fortify jmp buffer for x86-64 (PR #112769)

[Nick Desaulniers via libc-commits]

================
@@ -11,35 +11,87 @@
 #include "src/__support/macros/config.h"
 #include "src/setjmp/setjmp_impl.h"
 
+#if LIBC_COPT_SETJMP_FORTIFICATION
+#include "src/setjmp/checksum.h"
+#endif
+
 #if !defined(LIBC_TARGET_ARCH_IS_X86_64)
 #error "Invalid file include"
 #endif
 
-namespace LIBC_NAMESPACE_DECL {
+#if LIBC_COPT_SETJMP_FORTIFICATION
+#include "src/setjmp/x86_64/checksum.def"
+
+#define STORE_REG(SRC)                                                         \
+  "mov %%" #SRC ", %%rax\n\t"                                                  \
+  "xor %[mask], %%rax\n\t"                                                     \
+  "mov %%rax, %c[" #SRC "](%%rdi)\n\t" ACCUMULATE_CHECKSUM()
+
+#define STORE_RSP()                                                            \
+  "lea 8(%%rsp), %%rax\n\t"                                                    \
+  "xor %[mask], %%rax\n\t"                                                     \
+  "mov %%rax, %c[rsp](%%rdi)\n\t" ACCUMULATE_CHECKSUM()
+
+#define STORE_RIP()                                                            \
+  "mov (%%rsp), %%rax\n\t"                                                     \
+  "xor %[mask], %%rax\n\t"                                                     \
+  "mov %%rax, %c[rip](%%rdi)\n\t" ACCUMULATE_CHECKSUM()
+
+#define STORE_CHECKSUM() "mov %%rdx, %c[__chksum](%%rdi)\n\t"
+#else
+#define LOAD_CHKSUM_STATE_REGISTERS()
+#define STORE_REG(SRC) "mov %%" #SRC ", %c[" #SRC "](%%rdi)\n\t"
+#define STORE_RSP()                                                            \
+  "lea 8(%%rsp), %%rax\n\t"                                                    \
+  "mov %%rax, %c[rsp](%%rdi)\n\t"
+#define STORE_RIP()                                                            \
+  "mov (%%rsp), %%rax\n\t"                                                     \
+  "mov %%rax, %c[rip](%%rdi)\n\t"
+#define STORE_CHECKSUM()
+#endif
 
+namespace LIBC_NAMESPACE_DECL {
 [[gnu::naked]]
 LLVM_LIBC_FUNCTION(int, setjmp, (jmp_buf buf)) {
-  asm(R"(
-      mov %%rbx, %c[rbx](%%rdi)
-      mov %%rbp, %c[rbp](%%rdi)
-      mov %%r12, %c[r12](%%rdi)
-      mov %%r13, %c[r13](%%rdi)
-      mov %%r14, %c[r14](%%rdi)
-      mov %%r15, %c[r15](%%rdi)
-
-      lea 8(%%rsp), %%rax
-      mov %%rax, %c[rsp](%%rdi)
-
-      mov (%%rsp), %%rax
-      mov %%rax, %c[rip](%%rdi)
-
-      xorl %%eax, %%eax
-      retq)" ::[rbx] "i"(offsetof(__jmp_buf, rbx)),
-      [rbp] "i"(offsetof(__jmp_buf, rbp)), [r12] "i"(offsetof(__jmp_buf, r12)),
-      [r13] "i"(offsetof(__jmp_buf, r13)), [r14] "i"(offsetof(__jmp_buf, r14)),
-      [r15] "i"(offsetof(__jmp_buf, r15)), [rsp] "i"(offsetof(__jmp_buf, rsp)),
+  // use registers to make sure values propagate correctly across the asm blocks
----------------
nickdesaulniers wrote:

But rcx and rdx aren't used across the two asm statements.

https://github.com/llvm/llvm-project/pull/112769