Optimize process execution on Android

* exec/configure.ac (REENTRANT): Remove option for reentrancy.
(PROGRAM_COUNTER, HAVE_SECCOMP): Define register providing the
program counter and enable seccomp if its headers are available.

* exec/exec.c (write_load_command): Avoid defining unused
variable.
(exec_0): Remove code specific to REENTRANT configurations.

* exec/exec.h (struct exec_tracee) <exec_data, data_size>: New
fields for loader instructions and their size.

* exec/exec1.c (main): Call exec_init before forking.

* exec/mipsel-user.h (ELF_NGREG): Delete definition.
(struct mipsel_regs): Reduce number of gregs to 32, but
introduce separate fields for special registers.

* exec/trace.c (use_seccomp_p): New variable; defile to false if
!HAVE_SECCOMP.
(remove_tracee): Cease providing for non-reentrant
configurations.  Release executable data if present.
(handle_clone_prepare): Likewise.  Resume process with
PTRACE_CONT if seccomp-based interception is enabled.
(handle_clone, check_signal): Resume processes as above.
(handle_exec): Divide into two functions, with only rewriting
the system call and generating instructions for the loader
remaining in the first, and copying such instructions into the
loader's stack removed into a new function, `finish_exec'.
(finish_exec): New function.
(handle_readlinkat, handle_openat): Abolish non-REENTRANT
configurations.
(process_system_call): Divide exec system calls into two phases,
disambiguated by the value of tracee->waiting_for_syscall.  Typo
fixes.  Accommodate syscall-exit-stops where the signal was
initially intercepted by `seccomp_system_call'.
(interesting_syscalls): New array.
(ARRAYELTS): New macro.
(seccomp_system_call, establish_seccomp_filter): New function.
(tracing_execve) [HAVE_SECCOMP]: Establish a seccomp filter if
this is to be enabled.
(after_fork): Provide PTRACE_O_TRACESECCOMP.  Resume process
with PTRACE_CONT if seccomp-based interception is enabled.
(exec_waitpid): Resume process with PTRACE_CONT if seccomp-based
interception is enabled.  Dispatch stops identifying as
PTRACE_EVENT_SECCOMP to `seccomp_system_call'.
(exec_init): Establish whether it is possible to enable seccomp.

1 files changed, 5 insertions, 12 deletions

diff --git a/exec/exec.c b/exec/exec.c
index cbe22d4f18c..fad345c532c 100644
--- a/exec/exec.c
+++ b/exec/exec.c
@@ -292,7 +292,9 @@ write_load_command (program_header *header, bool use_alternate,
   struct exec_map_command command1;
   USER_WORD start, end;
   bool need_command1;
+#ifndef PAGE_MASK
   static long pagesize;
+#endif /* !PAGE_MASK */
 
   /* First, write the commands necessary to map the specified segment
      itself.
@@ -306,14 +308,14 @@ write_load_command (program_header *header, bool use_alternate,
 #ifdef HAVE_GETPAGESIZE
   if (!pagesize)
     pagesize = getpagesize ();
-#else /* HAVE_GETPAGESIZE */
+#else /* !HAVE_GETPAGESIZE */
   if (!pagesize)
     pagesize = sysconf (_SC_PAGESIZE);
-#endif /* HAVE_GETPAGESIZE */
+#endif /* !HAVE_GETPAGESIZE */
 
 #define PAGE_MASK (~(pagesize - 1))
 #define PAGE_SIZE (pagesize)
-#endif /* PAGE_MASK */
+#endif /* !PAGE_MASK */
 
   start = header->p_vaddr & PAGE_MASK;
   end = ((header->p_vaddr + header->p_filesz
@@ -895,10 +897,6 @@ format_pid (char *in, unsigned int pid)
    with #!; in that case, find the program to open and use that
    instead.
 
-   If REENTRANT is not defined, NAME is actually a buffer of size
-   PATH_MAX + 80.  In that case, copy over the file name actually
-   opened.
-
    Next, read the executable header, and add the necessary memory
    mappings for each file.  Finally, return the action data and its
    size in *SIZE.
@@ -976,11 +974,6 @@ exec_0 (char *name, struct exec_tracee *tracee,
           rewrite = buffer1 + link_size;
           remaining = buffer1 + sizeof buffer1 - rewrite - 1;
           memcpy (rewrite, name, strnlen (name, remaining));
-
-          /* Replace name with buffer1.  */
-#ifndef REENTRANT
-          strcpy (name, buffer1);
-#endif /* REENTRANT */
         }
     }