Reland "[libc] build fix for sigsetjmp (#137047)" (#137214)

Reland `sigsetjmp` patches with build fixes.

We wrap every target replying on the epilogue library into conditional
checks.

---------

Co-authored-by: Petr Hosek <phosek@google.com>

libc/config/linux/x86_64/entrypoints.txt

@@ -1060,6 +1060,8 @@ if(LLVM_LIBC_FULL_BUILD)
     # setjmp.h entrypoints
     libc.src.setjmp.longjmp
     libc.src.setjmp.setjmp
+    libc.src.setjmp.siglongjmp
+    libc.src.setjmp.sigsetjmp
 
     # stdio.h entrypoints
     libc.src.stdio.clearerr

libc/hdr/CMakeLists.txt

@@ -223,5 +223,14 @@ add_proxy_header_library(
     libc.include.wchar
 )
 
+# offsetof is a macro inside compiler resource header stddef.h
+add_proxy_header_library(
+  offsetof_macros
+  HDRS
+    offsetof_macros.h
+  FULL_BUILD_DEPENDS
+    libc.include.llvm-libc-macros.offsetof_macro
+)
+
 add_subdirectory(types)
 add_subdirectory(func)

libc/hdr/offsetof_macros.h

@@ -0,0 +1,23 @@
+//===-- Definition of macros for offsetof ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_HDR_OFFSETOF_MACROS_H
+#define LLVM_LIBC_HDR_OFFSETOF_MACROS_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-macros/offsetof-macro.h"
+
+#else // Overlay mode
+
+#define __need_offsetof
+#include <stddef.h>
+
+#endif // LLVM_LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_OFFSETOF_MACROS_H

libc/include/llvm-libc-types/CMakeLists.txt

@@ -39,7 +39,6 @@ add_header(gid_t HDR gid_t.h)
 add_header(uid_t HDR uid_t.h)
 add_header(imaxdiv_t HDR imaxdiv_t.h)
 add_header(ino_t HDR ino_t.h)
-add_header(jmp_buf HDR jmp_buf.h)
 add_header(mbstate_t HDR mbstate_t.h)
 add_header(mode_t HDR mode_t.h)
 add_header(mtx_t HDR mtx_t.h DEPENDS .__futex_word .__mutex_type)
@@ -83,6 +82,7 @@ add_header(union_sigval HDR union_sigval.h)
 add_header(siginfo_t HDR siginfo_t.h DEPENDS .union_sigval .pid_t .uid_t .clock_t)
 add_header(sig_atomic_t HDR sig_atomic_t.h)
 add_header(sigset_t HDR sigset_t.h DEPENDS libc.include.llvm-libc-macros.signal_macros)
+add_header(jmp_buf HDR jmp_buf.h DEPENDS .sigset_t)
 add_header(struct_sigaction HDR struct_sigaction.h DEPENDS .sigset_t .siginfo_t)
 add_header(struct_timespec HDR struct_timespec.h DEPENDS .time_t)
 add_header(

libc/include/llvm-libc-types/jmp_buf.h

@@ -9,6 +9,18 @@
 #ifndef LLVM_LIBC_TYPES_JMP_BUF_H
 #define LLVM_LIBC_TYPES_JMP_BUF_H
 
+// TODO: implement sigjmp_buf related functions for other architectures
+// Issue: https://github.com/llvm/llvm-project/issues/136358
+#if defined(__linux__)
+#if defined(__i386__) || defined(__x86_64__)
+#define __LIBC_HAS_SIGJMP_BUF
+#endif
+#endif
+
+#if defined(__LIBC_HAS_SIGJMP_BUF)
+#include "sigset_t.h"
+#endif
+
 typedef struct {
 #ifdef __x86_64__
   __UINT64_TYPE__ rbx;
@@ -50,8 +62,22 @@ typedef struct {
 #else
 #error "__jmp_buf not available for your target architecture."
 #endif
+#if defined(__LIBC_HAS_SIGJMP_BUF)
+  // return address
+  void *sig_retaddr;
+  // extra register buffer to avoid indefinite stack growth in sigsetjmp
+  void *sig_extra;
+  // signal masks
+  sigset_t sigmask;
+#endif
 } __jmp_buf;
 
 typedef __jmp_buf jmp_buf[1];
 
+#if defined(__LIBC_HAS_SIGJMP_BUF)
+typedef __jmp_buf sigjmp_buf[1];
+#endif
+
+#undef __LIBC_HAS_SIGJMP_BUF
+
 #endif // LLVM_LIBC_TYPES_JMP_BUF_H

libc/include/setjmp.yaml

@@ -21,3 +21,19 @@ functions:
       - _Returns_twice
     arguments:
       - type: jmp_buf
+  - name: sigsetjmp
+    standards:
+      - POSIX
+    return_type: int
+    attributes:
+      - _Returns_twice
+    arguments:
+      - type: sigjmp_buf
+      - type: int
+  - name: siglongjmp
+    standards:
+      - POSIX
+    return_type: _Noreturn void
+    arguments:
+      - type: sigjmp_buf
+      - type: int

libc/src/setjmp/CMakeLists.txt

@@ -1,3 +1,13 @@
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_object_library(
+    sigsetjmp_epilogue
+    ALIAS
+    DEPENDS
+      .${LIBC_TARGET_OS}.sigsetjmp_epilogue
+  )
+endif()
+
 if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_ARCHITECTURE})
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_ARCHITECTURE})
 endif()
@@ -15,3 +25,22 @@ add_entrypoint_object(
   DEPENDS
     .${LIBC_TARGET_ARCHITECTURE}.longjmp
 )
+
+if (TARGET libc.src.setjmp.sigsetjmp_epilogue)
+  add_entrypoint_object(
+    siglongjmp
+    SRCS
+      siglongjmp.cpp
+    HDRS
+      siglongjmp.h
+    DEPENDS
+      .longjmp
+  )
+
+  add_entrypoint_object(
+    sigsetjmp
+    ALIAS
+    DEPENDS
+      .${LIBC_TARGET_ARCHITECTURE}.sigsetjmp
+  )
+endif()

libc/src/setjmp/linux/CMakeLists.txt

@@ -0,0 +1,12 @@
+add_object_library(
+  sigsetjmp_epilogue
+  HDRS
+    ../sigsetjmp_epilogue.h
+  SRCS
+    sigsetjmp_epilogue.cpp
+  DEPENDS
+    libc.src.__support.common
+    libc.src.__support.OSUtil.osutil
+    libc.hdr.types.jmp_buf
+    libc.hdr.types.sigset_t
+)

libc/src/setjmp/linux/sigsetjmp_epilogue.cpp

@@ -0,0 +1,25 @@
+//===-- Implementation of sigsetjmp_epilogue ------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/setjmp/sigsetjmp_epilogue.h"
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/common.h"
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+[[gnu::returns_twice]] int sigsetjmp_epilogue(jmp_buf buffer, int retval) {
+  // If set is NULL, then the signal mask is unchanged (i.e., how is
+  // ignored), but the current value of the signal mask is nevertheless
+  // returned in oldset (if it is not NULL).
+  syscall_impl<long>(SYS_rt_sigprocmask, SIG_SETMASK,
+                     /* set= */ retval ? &buffer->sigmask : nullptr,
+                     /* old_set= */ retval ? nullptr : &buffer->sigmask,
+                     sizeof(sigset_t));
+  return retval;
+}
+} // namespace LIBC_NAMESPACE_DECL

libc/src/setjmp/setjmp_impl.h

@@ -29,7 +29,8 @@ namespace LIBC_NAMESPACE_DECL {
 #ifdef LIBC_COMPILER_IS_GCC
 [[gnu::nothrow]]
 #endif
-__attribute__((returns_twice)) int setjmp(jmp_buf buf);
+[[gnu::returns_twice]] int
+setjmp(jmp_buf buf);
 
 } // namespace LIBC_NAMESPACE_DECL
 

libc/src/setjmp/siglongjmp.cpp

@@ -0,0 +1,23 @@
+//===-- Implementation of siglongjmp --------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/setjmp/siglongjmp.h"
+#include "src/__support/common.h"
+#include "src/setjmp/longjmp.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+// siglongjmp is the same as longjmp. The additional recovery work is done in
+// the epilogue of the sigsetjmp function.
+// TODO: move this inside the TU of longjmp and making it an alias after
+//       sigsetjmp is implemented for all architectures.
+LLVM_LIBC_FUNCTION(void, siglongjmp, (jmp_buf buf, int val)) {
+  return LIBC_NAMESPACE::longjmp(buf, val);
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/setjmp/siglongjmp.h

@@ -0,0 +1,25 @@
+//===-- Implementation header for siglongjmp --------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SETJMP_SIGLONGJMP_H
+#define LLVM_LIBC_SRC_SETJMP_SIGLONGJMP_H
+
+#include "hdr/types/jmp_buf.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/compiler.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+#ifdef LIBC_COMPILER_IS_GCC
+[[gnu::nothrow]]
+#endif
+void siglongjmp(jmp_buf buf, int val);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SETJMP_SIGLONGJMP_H

libc/src/setjmp/sigsetjmp.h

@@ -0,0 +1,26 @@
+//===-- Implementation header for sigsetjmp ---------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SETJMP_SIGSETJMP_H
+#define LLVM_LIBC_SRC_SETJMP_SIGSETJMP_H
+
+#include "hdr/types/jmp_buf.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/compiler.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+#ifdef LIBC_COMPILER_IS_GCC
+[[gnu::nothrow]]
+#endif
+[[gnu::returns_twice]] int
+sigsetjmp(sigjmp_buf buf, int savesigs);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SETJMP_SIGSETJMP_H

libc/src/setjmp/sigsetjmp_epilogue.h

@@ -0,0 +1,19 @@
+//===-- Implementation header for sigsetjmp epilogue ------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SETJMP_SIGSETJMP_EPILOGUE_H
+#define LLVM_LIBC_SRC_SETJMP_SIGSETJMP_EPILOGUE_H
+
+#include "hdr/types/jmp_buf.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE_DECL {
+[[gnu::returns_twice]] int sigsetjmp_epilogue(jmp_buf buffer, int retval);
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SETJMP_SIGSETJMP_EPILOGUE_H

libc/src/setjmp/x86_64/CMakeLists.txt

@@ -5,10 +5,24 @@ add_entrypoint_object(
   HDRS
     ../setjmp_impl.h
   DEPENDS
+    libc.hdr.offsetof_macros
     libc.hdr.types.jmp_buf
-  COMPILE_OPTIONS
-    ${libc_opt_high_flag}
 )
+if (TARGET libc.src.setjmp.sigsetjmp_epilogue)
+  add_entrypoint_object(
+    sigsetjmp
+    SRCS
+      sigsetjmp.cpp
+    HDRS
+      ../sigsetjmp.h
+    DEPENDS
+      libc.hdr.types.jmp_buf
+      libc.hdr.types.sigset_t
+      libc.hdr.offsetof_macros
+      libc.src.setjmp.sigsetjmp_epilogue
+      libc.src.setjmp.setjmp
+  )
+endif()
 
 add_entrypoint_object(
   longjmp
@@ -18,7 +32,4 @@ add_entrypoint_object(
     ../longjmp.h
   DEPENDS
     libc.hdr.types.jmp_buf
-  COMPILE_OPTIONS
-    ${libc_opt_high_flag}
-    -fomit-frame-pointer
 )

libc/src/setjmp/x86_64/setjmp.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "include/llvm-libc-macros/offsetof-macro.h"
+#include "hdr/offsetof_macros.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
 #include "src/setjmp/setjmp_impl.h"

libc/src/setjmp/x86_64/sigsetjmp.cpp

@@ -0,0 +1,68 @@
+//===-- Implementation of sigsetjmp ---------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/setjmp/sigsetjmp.h"
+#include "hdr/offsetof_macros.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/setjmp/setjmp_impl.h"
+#include "src/setjmp/sigsetjmp_epilogue.h"
+
+#if !defined(LIBC_TARGET_ARCH_IS_X86)
+#error "Invalid file include"
+#endif
+namespace LIBC_NAMESPACE_DECL {
+#ifdef __i386__
+[[gnu::naked]]
+LLVM_LIBC_FUNCTION(int, sigsetjmp, (sigjmp_buf buf)) {
+  asm(R"(
+      mov 8(%%esp), %%ecx
+      jecxz .Lnosave
+
+      mov 4(%%esp), %%eax
+      pop %c[retaddr](%%eax)
+      mov %%ebx, %c[extra](%%eax)
+      mov %%eax, %%ebx
+      call %P[setjmp]
+      push %c[retaddr](%%ebx)
+      mov %%ebx,4(%%esp)
+      mov %%eax,8(%%esp)
+      mov %c[extra](%%ebx), %%ebx
+      jmp %P[epilogue]
+      
+.Lnosave:
+      jmp %P[setjmp])" ::[retaddr] "i"(offsetof(__jmp_buf, sig_retaddr)),
+      [extra] "i"(offsetof(__jmp_buf, sig_extra)), [setjmp] "X"(setjmp),
+      [epilogue] "X"(sigsetjmp_epilogue)
+      : "eax", "ebx", "ecx");
+}
+#endif
+[[gnu::naked]]
+LLVM_LIBC_FUNCTION(int, sigsetjmp, (sigjmp_buf, int)) {
+  asm(R"(
+      test %%esi, %%esi
+      jz .Lnosave
+
+      pop %c[retaddr](%%rdi)
+      mov %%rbx, %c[extra](%%rdi)
+      mov %%rdi, %%rbx
+      call %P[setjmp]
+      push %c[retaddr](%%rbx)
+      mov %%rbx, %%rdi
+      mov %%eax, %%esi
+      mov %c[extra](%%rdi), %%rbx
+      jmp %P[epilogue]
+      
+.Lnosave:
+      jmp %P[setjmp])" ::[retaddr] "i"(offsetof(__jmp_buf, sig_retaddr)),
+      [extra] "i"(offsetof(__jmp_buf, sig_extra)), [setjmp] "X"(setjmp),
+      [epilogue] "X"(sigsetjmp_epilogue)
+      : "rax", "rbx");
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/test/src/setjmp/CMakeLists.txt

@@ -17,3 +17,20 @@ add_libc_unittest(
     libc.src.setjmp.longjmp
     libc.src.setjmp.setjmp
 )
+
+add_libc_unittest(
+  sigsetjmp_test
+  SUITE
+    libc_setjmp_unittests
+  SRCS
+    sigsetjmp_test.cpp
+  CXX_STANDARD
+    20
+  DEPENDS
+    libc.src.setjmp.sigsetjmp
+    libc.src.setjmp.siglongjmp
+    libc.src.signal.sigprocmask
+    libc.src.string.memset
+    libc.src.string.memcmp
+    libc.hdr.types.sigset_t
+)

libc/test/src/setjmp/sigsetjmp_test.cpp

@@ -0,0 +1,88 @@
+//===-- Unittests for sigsetjmp and siglongjmp ----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/setjmp/siglongjmp.h"
+#include "src/setjmp/sigsetjmp.h"
+#include "src/signal/sigprocmask.h"
+#include "src/string/memcmp.h"
+#include "src/string/memset.h"
+#include "test/UnitTest/Test.h"
+
+constexpr int MAX_LOOP = 123;
+int longjmp_called = 0;
+
+void jump_back(jmp_buf buf, int n) {
+  longjmp_called++;
+  LIBC_NAMESPACE::siglongjmp(buf, n); // Will return |n| out of setjmp
+}
+
+TEST(LlvmLibcSetJmpTest, SigSetAndJumpBackSaveSigs) {
+  jmp_buf buf;
+  longjmp_called = 0;
+  volatile int n = 0;
+  sigset_t old;
+  sigset_t mask_all;
+  sigset_t recovered;
+  LIBC_NAMESPACE::memset(&mask_all, 0xFF, sizeof(mask_all));
+  LIBC_NAMESPACE::memset(&old, 0, sizeof(old));
+  LIBC_NAMESPACE::memset(&recovered, 0, sizeof(recovered));
+  LIBC_NAMESPACE::sigprocmask(0, nullptr, &old);
+  if (LIBC_NAMESPACE::sigsetjmp(buf, 1) <= MAX_LOOP) {
+    LIBC_NAMESPACE::sigprocmask(0, nullptr, &recovered);
+    ASSERT_EQ(0, LIBC_NAMESPACE::memcmp(&old, &recovered, sizeof(old)));
+    n = n + 1;
+    LIBC_NAMESPACE::sigprocmask(SIG_BLOCK, &mask_all, nullptr);
+    jump_back(buf, n);
+  }
+  ASSERT_EQ(longjmp_called, n);
+  ASSERT_EQ(n, MAX_LOOP + 1);
+}
+
+TEST(LlvmLibcSetJmpTest, SigSetAndJumpBackValOneSaveSigs) {
+  jmp_buf buf;
+  longjmp_called = 0;
+  sigset_t old;
+  sigset_t mask_all;
+  sigset_t recovered;
+  LIBC_NAMESPACE::memset(&mask_all, 0xFF, sizeof(mask_all));
+  LIBC_NAMESPACE::memset(&old, 0, sizeof(old));
+  LIBC_NAMESPACE::memset(&recovered, 0, sizeof(recovered));
+  LIBC_NAMESPACE::sigprocmask(0, nullptr, &old);
+  int val = LIBC_NAMESPACE::sigsetjmp(buf, 1);
+  if (val == 0) {
+    LIBC_NAMESPACE::sigprocmask(SIG_BLOCK, &mask_all, nullptr);
+    jump_back(buf, val);
+  }
+  LIBC_NAMESPACE::sigprocmask(0, nullptr, &recovered);
+  ASSERT_EQ(0, LIBC_NAMESPACE::memcmp(&old, &recovered, sizeof(old)));
+  ASSERT_EQ(longjmp_called, 1);
+  ASSERT_EQ(val, 1);
+}
+
+TEST(LlvmLibcSetJmpTest, SigSetAndJumpBackNoSaveSigs) {
+  jmp_buf buf;
+  longjmp_called = 0;
+  volatile int n = 0;
+  if (LIBC_NAMESPACE::sigsetjmp(buf, 0) <= MAX_LOOP) {
+    n = n + 1;
+    jump_back(buf, n);
+  }
+  ASSERT_EQ(longjmp_called, n);
+  ASSERT_EQ(n, MAX_LOOP + 1);
+}
+
+TEST(LlvmLibcSetJmpTest, SigSetAndJumpBackValOneNoSaveSigs) {
+  jmp_buf buf;
+  longjmp_called = 0;
+  int val = LIBC_NAMESPACE::sigsetjmp(buf, 0);
+  if (val == 0) {
+    jump_back(buf, val);
+  }
+  ASSERT_EQ(longjmp_called, 1);
+  ASSERT_EQ(val, 1);
+}