Use breakpad_getcontext on all Linux platforms missing getcontext

getcontext is also not available on musl libc, so generalize
breakpad_getcontext so it can be used as a fallback for non-Android
platforms as well.

On x86_64 and i386, ucontext_t uses an Android-specific offset for
storage of FP registers, since its sigset_t differs in size. So,
make the definition of MCONTEXT_FPREGS_MEM and UCONTEXT_FPREGS_MEM_OFFSET
conditional on whether we are building for Android.

On glibc and musl, signal.h and asm/sigcontext.h can't be included
together, so in breakpad_context_unittest.cc, only compare the libc
and kernel _fpstate when on Android.

Bug: google-breakpad:631
Change-Id: If81d73c4101bae946e9a3655b8d1c40a34ab6c38
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/2102135
Reviewed-by: Mike Frysinger <vapier@chromium.org>

src/client/linux/handler/exception_handler.cc

@@ -87,6 +87,7 @@
 #include <vector>
 
 #include "common/basictypes.h"
+#include "common/linux/breakpad_getcontext.h"
 #include "common/linux/linux_libc_support.h"
 #include "common/memory_allocator.h"
 #include "client/linux/log/log.h"

src/client/linux/microdump_writer/microdump_writer_unittest.cc

@@ -40,6 +40,7 @@
 #include "client/linux/handler/exception_handler.h"
 #include "client/linux/handler/microdump_extra_info.h"
 #include "client/linux/microdump_writer/microdump_writer.h"
+#include "common/linux/breakpad_getcontext.h"
 #include "common/linux/eintr_wrapper.h"
 #include "common/linux/ignore_ret.h"
 #include "common/scoped_ptr.h"

src/client/linux/minidump_writer/minidump_writer_unittest.cc

@@ -42,6 +42,7 @@
 #include "client/linux/minidump_writer/linux_dumper.h"
 #include "client/linux/minidump_writer/minidump_writer.h"
 #include "client/linux/minidump_writer/minidump_writer_unittest_utils.h"
+#include "common/linux/breakpad_getcontext.h"
 #include "common/linux/eintr_wrapper.h"
 #include "common/linux/file_id.h"
 #include "common/linux/ignore_ret.h"

src/common/common.gyp

@@ -33,7 +33,13 @@
         'defines': ['HAVE_MACH_O_NLIST_H'],
       }],
       ['OS=="linux"', {
-        'defines': ['HAVE_A_OUT_H'],
+        # Assume glibc.
+        'defines': ['HAVE_A_OUT_H', 'HAVE_GETCONTEXT'],
+        'sources!': [
+          'linux/breakpad_getcontext.S',
+          'linux/breakpad_getcontext.h',
+          'linux/breakpad_getcontext_unittest.cc',
+        ],
       }],
       ['OS!="android"', {'sources/': [['exclude', '(^|/)android/']]}],
       ['OS!="linux"', {'sources/': [['exclude', '(^|/)linux/']]}],
@@ -47,13 +53,11 @@
       'target_name': 'common',
       'type': 'static_library',
       'sources': [
-        'android/breakpad_getcontext.S',
         'android/include/elf.h',
         'android/include/link.h',
         'android/include/stab.h',
         'android/include/sys/procfs.h',
         'android/include/sys/user.h',
-        'android/include/ucontext.h',
         'android/testing/include/wchar.h',
         'android/testing/mkdtemp.h',
         'android/testing/pthread_fixes.h',
@@ -87,6 +91,8 @@
         'dwarf_line_to_module.h',
         'language.cc',
         'language.h',
+        'linux/breakpad_getcontext.S',
+        'linux/breakpad_getcontext.h',
         'linux/crc32.cc',
         'linux/crc32.h',
         'linux/dump_symbols.cc',
@@ -201,7 +207,6 @@
       'target_name': 'common_unittests',
       'type': 'executable',
       'sources': [
-        'android/breakpad_getcontext_unittest.cc',
         'byte_cursor_unittest.cc',
         'dwarf/bytereader_unittest.cc',
         'dwarf/dwarf2diehandler_unittest.cc',
@@ -210,6 +215,7 @@
         'dwarf_cfi_to_module_unittest.cc',
         'dwarf_cu_to_module_unittest.cc',
         'dwarf_line_to_module_unittest.cc',
+        'linux/breakpad_getcontext_unittest.cc',
         'linux/dump_symbols_unittest.cc',
         'linux/elf_core_dump_unittest.cc',
         'linux/elf_symbols_to_module_unittest.cc',

src/common/linux/breakpad_getcontext.S

@@ -28,9 +28,9 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // A minimalistic implementation of getcontext() to be used by
-// Google Breakpad on Android.
+// Google Breakpad when getcontext() is not available in libc.
 
-#include "common/android/ucontext_constants.h"
+#include "common/linux/ucontext_constants.h"
 
 /* int getcontext (ucontext_t *ucp) */
 

src/common/linux/breakpad_getcontext.h

@@ -27,22 +27,22 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#ifndef GOOGLE_BREAKPAD_COMMON_ANDROID_INCLUDE_UCONTEXT_H
-#define GOOGLE_BREAKPAD_COMMON_ANDROID_INCLUDE_UCONTEXT_H
+#ifndef GOOGLE_BREAKPAD_COMMON_LINUX_INCLUDE_UCONTEXT_H
+#define GOOGLE_BREAKPAD_COMMON_LINUX_INCLUDE_UCONTEXT_H
 
-#include <sys/cdefs.h>
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
 
-#ifdef __BIONIC_UCONTEXT_H
-#include <ucontext.h>
-#else
+#ifndef HAVE_GETCONTEXT
 
-#include <sys/ucontext.h>
+#include <signal.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif  // __cplusplus
 
-// Provided by src/android/common/breakpad_getcontext.S
+// Provided by src/common/linux/breakpad_getcontext.S
 int breakpad_getcontext(ucontext_t* ucp);
 
 #define getcontext(x)   breakpad_getcontext(x)
@@ -51,6 +51,6 @@ int breakpad_getcontext(ucontext_t* ucp);
 }  // extern "C"
 #endif  // __cplusplus
 
-#endif  // __BIONIC_UCONTEXT_H
+#endif  // HAVE_GETCONTEXT
 
-#endif  // GOOGLE_BREAKPAD_COMMON_ANDROID_INCLUDE_UCONTEXT_H
+#endif  // GOOGLE_BREAKPAD_COMMON_LINUX_INCLUDE_UCONTEXT_H

src/common/linux/breakpad_getcontext_unittest.cc

@@ -27,14 +27,18 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#if defined(__x86_64__)
+// asm/sigcontext.h can't be included with signal.h on glibc or
+// musl, so only compare _libc_fpstate and _fpstate on Android.
+#if defined(__ANDROID__) && defined(__x86_64__)
 #include <asm/sigcontext.h>
 #endif
 
 #include <sys/ucontext.h>
 
+#include <type_traits>
+
 #include "breakpad_googletest_includes.h"
-#include "common/android/ucontext_constants.h"
+#include "common/linux/ucontext_constants.h"
 
 template <int left, int right>
 struct CompileAssertEquals {
@@ -139,6 +143,8 @@ TEST(AndroidUContext, GRegsOffset) {
   // sigcontext is an analog to mcontext_t. The layout should be the same.
   COMPILE_ASSERT_EQ(offsetof(mcontext_t,fpregs),
                     offsetof(sigcontext,fpstate), sigcontext_fpstate);
+
+#if defined(__ANDROID__)
   // Check that _fpstate from asm/sigcontext.h is essentially the same
   // as _libc_fpstate.
   COMPILE_ASSERT_EQ(sizeof(_libc_fpstate), sizeof(_fpstate),
@@ -164,13 +170,15 @@ TEST(AndroidUContext, GRegsOffset) {
                     sigcontext_fpstate_stspace);
   COMPILE_ASSERT_EQ(offsetof(_libc_fpstate,_xmm), offsetof(_fpstate,xmm_space),
                     sigcontext_fpstate_xmm_space);
+#endif
 
   COMPILE_ASSERT_EQ(MCONTEXT_FPREGS_PTR,
                     offsetof(ucontext_t,uc_mcontext.fpregs),
                     mcontext_fpregs_ptr);
   COMPILE_ASSERT_EQ(MCONTEXT_FPREGS_MEM, offsetof(ucontext_t,__fpregs_mem),
                     mcontext_fpregs_mem);
-  COMPILE_ASSERT_EQ(FPREGS_OFFSET_MXCSR, offsetof(_libc_fpstate,mxcsr),
+  COMPILE_ASSERT_EQ(FPREGS_OFFSET_MXCSR,
+                    offsetof(std::remove_pointer<fpregset_t>::type,mxcsr),
                     fpregs_offset_mxcsr);
   COMPILE_ASSERT_EQ(UCONTEXT_SIGMASK_OFFSET, offsetof(ucontext_t, uc_sigmask),
                     ucontext_sigmask);

src/common/linux/ucontext_constants.h

@@ -31,14 +31,15 @@
 // Its purpose is to contain constants that must match the offsets of
 // various fields in ucontext_t.
 //
-// They should match the definitions from
-// src/common/android/include/sys/ucontext.h
+// They should match the definitions from signal.h.
 //
-// Used by src/common/android/breakpad_getcontext.S
-// Tested by src/common/android/testing/breakpad_getcontext_unittest.cc
+// Used by src/common/linux/breakpad_getcontext.S
+// Tested by src/common/linux/breakpad_getcontext_unittest.cc
+//
+// This header should not be used by anything else.
 
-#ifndef GOOGLEBREAKPAD_COMMON_ANDROID_UCONTEXT_CONSTANTS_H
-#define GOOGLEBREAKPAD_COMMON_ANDROID_UCONTEXT_CONSTANTS_H
+#ifndef GOOGLEBREAKPAD_COMMON_LINUX_UCONTEXT_CONSTANTS_H
+#define GOOGLEBREAKPAD_COMMON_LINUX_UCONTEXT_CONSTANTS_H
 
 #if defined(__arm__)
 
@@ -93,7 +94,11 @@
 #define  UCONTEXT_SIGMASK_OFFSET   108
 
 #define  UCONTEXT_FPREGS_OFFSET       96
+#if defined(__BIONIC__)
 #define  UCONTEXT_FPREGS_MEM_OFFSET   116
+#else
+#define  UCONTEXT_FPREGS_MEM_OFFSET   236
+#endif
 
 #elif defined(__mips__)
 
@@ -134,7 +139,11 @@
 #define MCONTEXT_GREGS_RSP   160
 #define MCONTEXT_GREGS_RIP   168
 #define MCONTEXT_FPREGS_PTR  224
+#if defined(__BIONIC__)
 #define MCONTEXT_FPREGS_MEM  304
+#else
+#define MCONTEXT_FPREGS_MEM  424
+#endif
 #define FPREGS_OFFSET_MXCSR  24
 
 #else

src/config.h.in

@@ -9,6 +9,9 @@
 /* define if the compiler supports basic C++11 syntax */
 #undef HAVE_CXX11
 
+/* Define to 1 if you have the `getcontext' function. */
+#undef HAVE_GETCONTEXT
+
 /* Define to 1 if you have the `getrandom' function. */
 #undef HAVE_GETRANDOM