Added support for sigreturn() and rt_sigreturn(). On x86-32, this is...

sandbox/linux/seccomp/library.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #define XOPEN_SOURCE 500
 #include <algorithm>
 #include <elf.h>
 #include <errno.h>
 #include <errno.h>
 #include <fcntl.h>
@@ skipping 817 matching lines @@
     *__kernel_vsyscall = '\xE9';
     *reinterpret_cast<long *>(__kernel_vsyscall + 1) =
         reinterpret_cast<char *>(&syscallWrapper) -
         reinterpret_cast<char *>(__kernel_vsyscall + 5);
   }
   if (__kernel_sigreturn) {
     // Replace the sigreturn() system call with a jump to code that does:
     //
     // 58                POP %eax
     // B8 77 00 00 00    MOV $0x77, %eax
-    // E9 .. .. .. ..    JMP syscallWrapper
+    // E8 .. .. .. ..    CALL syscallWrapper
     char* dest = getScratchSpace(maps_, __kernel_sigreturn, 11, extraSpace,
                                  extraLength);
-    memcpy(dest, "\x58\xB8\x77\x00\x00\x00\xE9", 7);
-    *reinterpret_cast<char *>(dest + 7) =
-        reinterpret_cast<char *>(&syscallWrapper) -
-        reinterpret_cast<char *>(dest + 11);
+    memcpy(dest, "\x58\xB8\x77\x00\x00\x00\xE8", 7);
+    *reinterpret_cast<long *>(dest + 7) =
+        reinterpret_cast<char *>(&syscallWrapper) - dest - 11;;
     *__kernel_sigreturn = '\xE9';
-    *reinterpret_cast<char *>(__kernel_sigreturn + 1) =
-        dest - reinterpret_cast<char *>(__kernel_sigreturn + 5);
+    *reinterpret_cast<long *>(__kernel_sigreturn + 1) =
+        dest - reinterpret_cast<char *>(__kernel_sigreturn) - 5;
   }
   if (__kernel_rt_sigreturn) {
     // Replace the rt_sigreturn() system call with a jump to code that does:
     //
     // B8 AD 00 00 00    MOV $0xAD, %eax
-    // E9 .. .. .. ..    JMP syscallWrapper
+    // E8 .. .. .. ..    CALL syscallWrapper
     char* dest = getScratchSpace(maps_, __kernel_rt_sigreturn, 10, extraSpace,
                                  extraLength);
-    memcpy(dest, "\xB8\xAD\x00\x00\x00\xE9", 6);
-    *reinterpret_cast<char *>(dest + 6) =
-        reinterpret_cast<char *>(&syscallWrapper) -
-        reinterpret_cast<char *>(dest + 10);
+    memcpy(dest, "\xB8\xAD\x00\x00\x00\xE8", 6);
+    *reinterpret_cast<long *>(dest + 6) =
+        reinterpret_cast<char *>(&syscallWrapper) - dest - 10;
     *__kernel_rt_sigreturn = '\xE9';
-    *reinterpret_cast<char *>(__kernel_rt_sigreturn + 1) =
-        dest - reinterpret_cast<char *>(__kernel_rt_sigreturn + 5);
+    *reinterpret_cast<long *>(__kernel_rt_sigreturn + 1) =
+        dest - reinterpret_cast<char *>(__kernel_rt_sigreturn) - 5;
   }
   #endif
 }
 
 int Library::patchVSystemCalls() {
   #if defined(__x86_64__)
   // VSyscalls live in a shared 4kB page at the top of the address space. This
   // page cannot be unmapped nor remapped. We have to create a copy within
   // 2GB of the page, and rewrite all IP-relative accesses to shared variables.
   // As the top of the address space is not accessible by mmap(), this means
@@ skipping 329 matching lines @@
   }
   iter = symbols_.find("__kernel_rt_sigreturn");
   if (iter != symbols_.end() && iter->second.st_value) {
     __kernel_rt_sigreturn = asr_offset_ + iter->second.st_value;
   }
 
   return true;
 }
 
 } // namespace