[PATCH 2/2] Add a test for setjmp/longjmp within user context

[Noah Goldstein]

On Thu, Dec 14, 2023 at 1:37 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> Verify that setjmp/longjmp works correctly within a user context.
> ---
>  stdlib/Makefile           |   1 +
>  stdlib/tst-setcontext11.c | 178 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 179 insertions(+)
>  create mode 100644 stdlib/tst-setcontext11.c
>
> diff --git a/stdlib/Makefile b/stdlib/Makefile
> index 8c6249aab4..0b5ef699a2 100644
> --- a/stdlib/Makefile
> +++ b/stdlib/Makefile
> @@ -235,6 +235,7 @@ tests := \
>    tst-setcontext8 \
>    tst-setcontext9 \
>    tst-setcontext10 \
> +  tst-setcontext11 \
>    tst-strfmon_l \
>    tst-strfrom \
>    tst-strfrom-locale \
> diff --git a/stdlib/tst-setcontext11.c b/stdlib/tst-setcontext11.c
> new file mode 100644
> index 0000000000..5f5df5b81b
> --- /dev/null
> +++ b/stdlib/tst-setcontext11.c
> @@ -0,0 +1,178 @@
> +/* Check setjmp/longjmp within user context.
> +   Copyright (C) 2023 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 <errno.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <setjmp.h>
> +#include <ucontext.h>
> +#include <unistd.h>
> +
> +static ucontext_t ctx[3];
> +static jmp_buf jmpbuf;
> +
> +static int was_in_f1;
> +static int was_in_f2;
> +static int longjmp_called;
> +
> +static char st2[32768];
> +
> +static void
> +f1 (int a0, int a1, int a2, int a3)
> +{
> +  printf ("start f1(a0=%x,a1=%x,a2=%x,a3=%x)\n", a0, a1, a2, a3);
> +
> +  if (a0 != 1 || a1 != 2 || a2 != 3 || a3 != -4)
> +    {
> +      puts ("arg mismatch");
> +      exit (EXIT_FAILURE);
> +    }
> +
> +  if (swapcontext (&ctx[1], &ctx[2]) != 0)
> +    {
> +      printf ("%s: swapcontext: %m\n", __FUNCTION__);
> +      exit (EXIT_FAILURE);
> +    }
> +  puts ("finish f1");
> +  was_in_f1 = 1;
> +}
> +
> +static void
> +__attribute__ ((noinline, noclone))
> +call_longjmp (void)
> +{
> +  longjmp_called = 1;
> +  longjmp (jmpbuf, 1);
> +}
> +
> +static void
> +f2 (void)
> +{
> +  if (!longjmp_called)
> +    {
> +      if (setjmp (jmpbuf) == 0)
> +       call_longjmp ();
> +    }
> +
> +  puts ("start f2");
> +  if (swapcontext (&ctx[2], &ctx[1]) != 0)
> +    {
> +      printf ("%s: swapcontext: %m\n", __FUNCTION__);
> +      exit (EXIT_FAILURE);
> +    }
> +  puts ("finish f2");
> +  was_in_f2 = 1;
> +}
> +
> +volatile int global;
> +static int back_in_main;
> +
> +static void
> +check_called (void)
> +{
> +  if (back_in_main == 0)
> +    {
> +      puts ("program did not reach main again");
> +      _exit (EXIT_FAILURE);
> +    }
> +}
> +
> +static int
> +do_test (void)
> +{
> +  atexit (check_called);
> +
> +  char st1[32768];
> +
> +  puts ("making contexts");
> +  if (getcontext (&ctx[1]) != 0)
> +    {
> +      if (errno == ENOSYS)
> +       {
> +         back_in_main = 1;
> +         exit (EXIT_SUCCESS);
> +       }
> +
> +      printf ("%s: getcontext: %m\n", __FUNCTION__);
> +      exit (EXIT_FAILURE);
> +    }
> +
> +  /* Play some tricks with this context.  */
> +  if (++global == 1)
> +    if (setcontext (&ctx[1]) != 0)
> +      {
> +       printf ("%s: setcontext: %m\n", __FUNCTION__);
> +       exit (EXIT_FAILURE);
> +      }
> +  if (global != 2)
> +    {
> +      printf ("%s: 'global' not incremented twice\n", __FUNCTION__);
> +      exit (EXIT_FAILURE);
> +    }
> +
> +  ctx[1].uc_stack.ss_sp = st1;
> +  ctx[1].uc_stack.ss_size = sizeof st1;
> +  ctx[1].uc_link = &ctx[0];
> +  {
> +    ucontext_t tempctx = ctx[1];
> +    makecontext (&ctx[1], (void (*) (void)) f1, 4, 1, 2, 3, -4);
> +
> +    /* Without this check, a stub makecontext can make us spin forever.  */
> +    if (memcmp (&tempctx, &ctx[1], sizeof ctx[1]) == 0)
> +      {
> +       puts ("makecontext was a no-op, presuming not implemented");
> +       return 0;
> +      }
> +  }
> +
> +  if (getcontext (&ctx[2]) != 0)
> +    {
> +      printf ("%s: second getcontext: %m\n", __FUNCTION__);
> +      exit (EXIT_FAILURE);
> +    }
> +  ctx[2].uc_stack.ss_sp = st2;
> +  ctx[2].uc_stack.ss_size = sizeof st2;
> +  ctx[2].uc_link = &ctx[1];
> +  makecontext (&ctx[2], f2, 0);
> +
> +  puts ("swapping contexts");
> +  if (swapcontext (&ctx[0], &ctx[2]) != 0)
> +    {
> +      printf ("%s: swapcontext: %m\n", __FUNCTION__);
> +      exit (EXIT_FAILURE);
> +    }
> +  puts ("back at main program");
> +  back_in_main = 1;
> +
> +  if (was_in_f1 == 0)
> +    {
> +      puts ("didn't reach f1");
> +      exit (EXIT_FAILURE);
> +    }
> +  if (was_in_f2 == 0)
> +    {
> +      puts ("didn't reach f2");
> +      exit (EXIT_FAILURE);
> +    }
> +
> +  puts ("test succeeded");
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
> --
> 2.43.0
>

LGTM.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>