Skip to content

[libc][setjmp] make x86_64 longjmp naked #112581

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Oct 17, 2024
Merged

[libc][setjmp] make x86_64 longjmp naked #112581

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
6ca41d9
[libc][setjmp] make x86_64 longjmp naked
nickdesaulniers Oct 16, 2024
9908066
reformat
nickdesaulniers Oct 16, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 13 additions & 0 deletions libc/src/setjmp/longjmp.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -11,9 +11,22 @@

#include "hdr/types/jmp_buf.h"
#include "src/__support/macros/config.h"
#include "src/__support/macros/properties/compiler.h"

namespace LIBC_NAMESPACE_DECL {

// TODO(https://github.com/llvm/llvm-project/issues/112427)
// Some of the architecture-specific definitions are marked `naked`, which in
// GCC implies `nothrow`.
//
// Right now, our aliases aren't marked `nothrow`, so we wind up in a situation
// where clang will emit -Wmissing-exception-spec if we add `nothrow` here, but
// GCC will emit -Wmissing-attributes here without `nothrow`. We need to update
// LLVM_LIBC_FUNCTION to denote when a function throws or not.

#ifdef LIBC_COMPILER_IS_GCC
[[gnu::nothrow]]
#endif
void longjmp(jmp_buf buf, int val);

} // namespace LIBC_NAMESPACE_DECL
Expand Down
43 changes: 20 additions & 23 deletions libc/src/setjmp/x86_64/longjmp.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
//===----------------------------------------------------------------------===//

#include "src/setjmp/longjmp.h"
#include "include/llvm-libc-macros/offsetof-macro.h"
#include "src/__support/common.h"
#include "src/__support/macros/config.h"

Expand All @@ -16,30 +17,26 @@

namespace LIBC_NAMESPACE_DECL {

LLVM_LIBC_FUNCTION(void, longjmp, (jmp_buf buf, int val)) {
register __UINT64_TYPE__ rbx __asm__("rbx");
register __UINT64_TYPE__ rbp __asm__("rbp");
register __UINT64_TYPE__ r12 __asm__("r12");
register __UINT64_TYPE__ r13 __asm__("r13");
register __UINT64_TYPE__ r14 __asm__("r14");
register __UINT64_TYPE__ r15 __asm__("r15");
register __UINT64_TYPE__ rsp __asm__("rsp");
register __UINT64_TYPE__ rax __asm__("rax");
[[gnu::naked]]
LLVM_LIBC_FUNCTION(void, longjmp, (jmp_buf, int)) {
asm(R"(
cmpl $0x1, %%esi
adcl $0x0, %%esi
movq %%rsi, %%rax

// ABI requires that the return value should be stored in rax. So, we store
// |val| in rax. Note that this has to happen before we restore the registers
// from values in |buf|. Otherwise, once rsp and rbp are updated, we cannot
// read |val|.
val = val == 0 ? 1 : val;
LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rax) : "m"(val) :);
LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rbx) : "m"(buf->rbx) :);
LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rbp) : "m"(buf->rbp) :);
LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(r12) : "m"(buf->r12) :);
LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(r13) : "m"(buf->r13) :);
LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(r14) : "m"(buf->r14) :);
LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(r15) : "m"(buf->r15) :);
LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rsp) : "m"(buf->rsp) :);
LIBC_INLINE_ASM("jmp *%0\n\t" : : "m"(buf->rip));
movq %c[rbx](%%rdi), %%rbx
movq %c[rbp](%%rdi), %%rbp
movq %c[r12](%%rdi), %%r12
movq %c[r13](%%rdi), %%r13
movq %c[r14](%%rdi), %%r14
movq %c[r15](%%rdi), %%r15
movq %c[rsp](%%rdi), %%rsp
jmpq *%c[rip](%%rdi)
)" ::[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)),
[rip] "i"(offsetof(__jmp_buf, rip)));
}

} // namespace LIBC_NAMESPACE_DECL
Loading