Re: [PATCH v3 10/37] csu: Move calling main out of __libc_start_main_impl

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 16/03/2021 14:29, Florian Weimer via Libc-alpha wrote:
> This code depends on whether glibc has unwinding support for
> a particular port.

LGTM.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  csu/libc-start.c                       | 74 ++--------------------
>  sysdeps/generic/libc_start_call_main.h | 24 +++++++
>  sysdeps/nptl/libc_start_call_main.h    | 88 ++++++++++++++++++++++++++
>  3 files changed, 116 insertions(+), 70 deletions(-)
>  create mode 100644 sysdeps/generic/libc_start_call_main.h
>  create mode 100644 sysdeps/nptl/libc_start_call_main.h
> 
> diff --git a/csu/libc-start.c b/csu/libc-start.c
> index 05ff7afddf..8688cba76d 100644
> --- a/csu/libc-start.c
> +++ b/csu/libc-start.c
> @@ -58,12 +58,6 @@ uintptr_t __pointer_chk_guard_local
>  # endif
>  #endif
>  
> -#ifdef HAVE_PTR_NTHREADS
> -/* We need atomic operations.  */
> -# include <atomic.h>
> -#endif
> -
> -
>  #ifndef SHARED
>  # include <link.h>
>  # include <dl-irel.h>
> @@ -123,6 +117,9 @@ apply_irel (void)
>  # define ARCH_INIT_CPU_FEATURES()
>  #endif
>  
> +/* Obtain the definition of __libc_start_call_main.  */
> +#include <libc_start_call_main.h>
> +
>  #ifdef SHARED
>  /* Initialization for dynamic executables.  Find the main executable
>     link map and run its init functions.  */
> @@ -245,9 +242,6 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
>  		 void (*fini) (void),
>  		 void (*rtld_fini) (void), void *stack_end)
>  {
> -  /* Result of the 'main' function.  */
> -  int result;
> -
>  #ifndef SHARED
>    char **ev = &argv[argc + 1];
>  
> @@ -413,68 +407,8 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
>  #ifndef SHARED
>    _dl_debug_initialize (0, LM_ID_BASE);
>  #endif
> -#ifdef HAVE_CLEANUP_JMP_BUF
> -  /* Memory for the cancellation buffer.  */
> -  struct pthread_unwind_buf unwind_buf;
> -
> -  int not_first_call;
> -  DIAG_PUSH_NEEDS_COMMENT;
> -#if __GNUC_PREREQ (7, 0)
> -  /* This call results in a -Wstringop-overflow warning because struct
> -     pthread_unwind_buf is smaller than jmp_buf.  setjmp and longjmp
> -     do not use anything beyond the common prefix (they never access
> -     the saved signal mask), so that is a false positive.  */
> -  DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overflow=");
> -#endif
> -  not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
> -  DIAG_POP_NEEDS_COMMENT;
> -  if (__glibc_likely (! not_first_call))
> -    {
> -      struct pthread *self = THREAD_SELF;
> -
> -      /* Store old info.  */
> -      unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
> -      unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
> -
> -      /* Store the new cleanup handler info.  */
> -      THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
> -
> -      /* Run the program.  */
> -      result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
> -    }
> -  else
> -    {
> -      /* Remove the thread-local data.  */
> -# ifdef SHARED
> -      PTHFCT_CALL (ptr__nptl_deallocate_tsd, ());
> -# else
> -      extern void __nptl_deallocate_tsd (void) __attribute ((weak));
> -      __nptl_deallocate_tsd ();
> -# endif
> -
> -      /* One less thread.  Decrement the counter.  If it is zero we
> -	 terminate the entire process.  */
> -      result = 0;
> -# ifdef SHARED
> -      unsigned int *ptr = __libc_pthread_functions.ptr_nthreads;
> -#  ifdef PTR_DEMANGLE
> -      PTR_DEMANGLE (ptr);
> -#  endif
> -# else
> -      extern unsigned int __nptl_nthreads __attribute ((weak));
> -      unsigned int *const ptr = &__nptl_nthreads;
> -# endif
> -
> -      if (! atomic_decrement_and_test (ptr))
> -	/* Not much left to do but to exit the thread, not the process.  */
> -	__exit_thread ();
> -    }
> -#else
> -  /* Nothing fancy, just call the function.  */
> -  result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
> -#endif
>  
> -  exit (result);
> +  __libc_start_call_main (main, argc, argv MAIN_AUXVEC_PARAM);
>  }
>  
>  /* Starting with glibc 2.34, the init parameter is always NULL.  Older

Ok.

> diff --git a/sysdeps/generic/libc_start_call_main.h b/sysdeps/generic/libc_start_call_main.h
> new file mode 100644
> index 0000000000..8a06eec4a3
> --- /dev/null
> +++ b/sysdeps/generic/libc_start_call_main.h
> @@ -0,0 +1,24 @@
> +/* Invoking main from __libc_start.  Generic version without unwinding.
> +   Copyright (C) 1998-2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +_Noreturn static __always_inline void
> +__libc_start_call_main (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
> +                        int argc, char **argv MAIN_AUXVEC_DECL)
> +{
> +  exit (main (argc, argv, __environ MAIN_AUXVEC_PARAM));
> +}

Ok.

> diff --git a/sysdeps/nptl/libc_start_call_main.h b/sysdeps/nptl/libc_start_call_main.h
> new file mode 100644
> index 0000000000..5218e7ab1e
> --- /dev/null
> +++ b/sysdeps/nptl/libc_start_call_main.h
> @@ -0,0 +1,88 @@
> +/* Invoking main from __libc_start_main.  nptl version.
> +   Copyright (C) 1998-2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <atomic.h>
> +
> +_Noreturn static void
> +__libc_start_call_main (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
> +                        int argc, char **argv
> +#ifdef LIBC_START_MAIN_AUXVEC_ARG
> +                            , ElfW(auxv_t) *auxvec
> +#endif
> +                        )
> +{
> +  int result;
> +
> +  /* Memory for the cancellation buffer.  */
> +  struct pthread_unwind_buf unwind_buf;
> +
> +  int not_first_call;
> +  DIAG_PUSH_NEEDS_COMMENT;
> +#if __GNUC_PREREQ (7, 0)
> +  /* This call results in a -Wstringop-overflow warning because struct
> +     pthread_unwind_buf is smaller than jmp_buf.  setjmp and longjmp
> +     do not use anything beyond the common prefix (they never access
> +     the saved signal mask), so that is a false positive.  */
> +  DIAG_IGNORE_NEEDS_COMMENT (11, "-Wstringop-overflow=");
> +#endif
> +  not_first_call = setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
> +  DIAG_POP_NEEDS_COMMENT;
> +  if (__glibc_likely (! not_first_call))
> +    {
> +      struct pthread *self = THREAD_SELF;
> +
> +      /* Store old info.  */
> +      unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
> +      unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
> +
> +      /* Store the new cleanup handler info.  */
> +      THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
> +
> +      /* Run the program.  */
> +      result = main (argc, argv, __environ MAIN_AUXVEC_PARAM);
> +    }
> +  else
> +    {
> +      /* Remove the thread-local data.  */
> +# ifdef SHARED
> +      PTHFCT_CALL (ptr__nptl_deallocate_tsd, ());
> +# else
> +      extern void __nptl_deallocate_tsd (void) __attribute ((weak));
> +      __nptl_deallocate_tsd ();
> +# endif
> +
> +      /* One less thread.  Decrement the counter.  If it is zero we
> +         terminate the entire process.  */
> +      result = 0;
> +# ifdef SHARED
> +      unsigned int *ptr = __libc_pthread_functions.ptr_nthreads;
> +#  ifdef PTR_DEMANGLE
> +      PTR_DEMANGLE (ptr);
> +#  endif
> +# else
> +      extern unsigned int __nptl_nthreads __attribute ((weak));
> +      unsigned int *const ptr = &__nptl_nthreads;
> +# endif
> +
> +      if (! atomic_decrement_and_test (ptr))
> +        /* Not much left to do but to exit the thread, not the process.  */
> +        __exit_thread ();
> +    }
> +
> +  exit (result);
> +}
> 

Ok.