Update from https://crrev.com/328418

sandbox/linux/seccomp-bpf/syscall.cc

 // Copyright (c) 2012 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.
 
 #include "sandbox/linux/seccomp-bpf/syscall.h"
 
 #include <errno.h>
 #include <stdint.h>
 
 #include "base/logging.h"
@@ skipping 115 matching lines @@
     // interworking. That's OK, as we don't make any of the assembly
     // symbols public. They are all local to this file.
     ".text\n"
     ".align 2\n"
     ".type SyscallAsm, %function\n"
 #if defined(__thumb__)
     ".thumb_func\n"
 #else
     ".arm\n"
 #endif
-    "SyscallAsm:.fnstart\n"
+    "SyscallAsm:\n"
+#if !defined(__native_client_nonsfi__)
+    // .fnstart and .fnend pseudo operations creates unwind table.
+    // It also creates a reference to the symbol __aeabi_unwind_cpp_pr0, which
+    // is not provided by PNaCl toolchain. Disable it.
+    ".fnstart\n"
+#endif
     "@ args = 0, pretend = 0, frame = 8\n"
     "@ frame_needed = 1, uses_anonymous_args = 0\n"
 #if defined(__thumb__)
     ".cfi_startproc\n"
     "push {r7, lr}\n"
+    ".save {r7, lr}\n"
     ".cfi_offset 14, -4\n"
     ".cfi_offset  7, -8\n"
-    "mov r7, sp\n"
-    ".cfi_def_cfa_register 7\n"
     ".cfi_def_cfa_offset 8\n"
 #else
     "stmfd sp!, {fp, lr}\n"
     "add fp, sp, #4\n"
 #endif
     // Check if "r0" is negative. If so, do not attempt to make a
     // system call. Instead, compute the return address that is visible
     // to the kernel after we execute "swi 0". This address can be
     // used as a marker that BPF code inspects.
     "cmp r0, #0\n"
@@ skipping 14 matching lines @@
     // Enter the kernel
     "swi 0\n"
 // Restore the frame pointer. Also restore the program counter from
 // the link register; this makes us return to the caller.
 #if defined(__thumb__)
     "2:pop {r7, pc}\n"
     ".cfi_endproc\n"
 #else
     "2:ldmfd sp!, {fp, pc}\n"
 #endif
+#if !defined(__native_client_nonsfi__)
+    // Do not use .fnstart and .fnend for PNaCl toolchain. See above comment,
+    // for more details.
     ".fnend\n"
+#endif
     "9:.size SyscallAsm, 9b-SyscallAsm\n"
 #elif defined(__mips__)
     ".text\n"
     ".align 4\n"
     ".type SyscallAsm, @function\n"
     "SyscallAsm:.ent SyscallAsm\n"
     ".frame  $sp, 40, $ra\n"
     ".set   push\n"
     ".set   noreorder\n"
     "addiu  $sp, $sp, -40\n"
@@ skipping 212 matching lines @@
   }
 
   // Set an error status so it can be used outside of this function
   *err_ret = err_stat;
 
   return ret;
 }
 #endif  // defined(__mips__)
 
 }  // namespace sandbox