Re: [PATCH] S390: Sync ptrace.h with kernel. [BZ #21539]

["Dmitry V. Levin" <ldv at altlinux dot org>]

On Tue, Jun 06, 2017 at 12:17:33PM +0200, Stefan Liebler wrote:
[...]
> diff --git a/sysdeps/unix/sysv/linux/s390/sys/ptrace.h b/sysdeps/unix/sysv/linux/s390/sys/ptrace.h
> index 7caf101..88079fc 100644
> --- a/sysdeps/unix/sysv/linux/s390/sys/ptrace.h
> +++ b/sysdeps/unix/sysv/linux/s390/sys/ptrace.h
> @@ -89,25 +89,9 @@ enum __ptrace_request
>    PTRACE_SINGLESTEP = 9,
>  #define PT_STEP PTRACE_SINGLESTEP
>  
> -  /* Get all general purpose registers used by a processes.
> -     This is not supported on all machines.  */
> -   PTRACE_GETREGS = 12,
> -#define PT_GETREGS PTRACE_GETREGS
> -
> -  /* Set all general purpose registers used by a processes.
> -     This is not supported on all machines.  */
> -   PTRACE_SETREGS = 13,
> -#define PT_SETREGS PTRACE_SETREGS
> -
> -  /* Get all floating point registers used by a processes.
> -     This is not supported on all machines.  */
> -   PTRACE_GETFPREGS = 14,
> -#define PT_GETFPREGS PTRACE_GETFPREGS
> -
> -  /* Set all floating point registers used by a processes.
> -     This is not supported on all machines.  */
> -   PTRACE_SETFPREGS = 15,
> -#define PT_SETFPREGS PTRACE_SETFPREGS
> +  /* Execute process until next taken branch.  */
> +  PTRACE_SINGLEBLOCK = 12,
> +#define PT_STEPBLOCK PTRACE_SINGLEBLOCK
>  
>    /* Attach to a process that is already running. */
>    PTRACE_ATTACH = 16,
> @@ -167,8 +151,26 @@ enum __ptrace_request
>    PTRACE_SETSIGMASK = 0x420b,
>  #define PTRACE_SETSIGMASK PTRACE_SETSIGMASK
>  
> -  PTRACE_SECCOMP_GET_FILTER = 0x420c
> +  PTRACE_SECCOMP_GET_FILTER = 0x420c,
>  #define PTRACE_SECCOMP_GET_FILTER PTRACE_SECCOMP_GET_FILTER
> +
> +  PTRACE_PEEKUSR_AREA = 0x5000,
> +#define PTRACE_PEEKUSR_AREA PTRACE_PEEKUSR_AREA
> +
> +  PTRACE_POKEUSR_AREA = 0x5001,
> +#define PTRACE_POKEUSR_AREA PTRACE_POKEUSR_AREA
> +
> +  PTRACE_GET_LAST_BREAK = 0x5006,
> +#define PTRACE_GET_LAST_BREAK PTRACE_GET_LAST_BREAK
> +
> +  PTRACE_ENABLE_TE = 0x5009,
> +#define PTRACE_ENABLE_TE PTRACE_ENABLE_TE
> +
> +  PTRACE_DISABLE_TE = 0x5010,
> +#define PTRACE_DISABLE_TE PTRACE_DISABLE_TE
> +
> +  PTRACE_TE_ABORT_RAND = 0x5011
> +#define PTRACE_TE_ABORT_RAND PTRACE_TE_ABORT_RAND
>  };

The sys/ptrace.h part of the change looks fine.

> diff --git a/sysdeps/unix/sysv/linux/s390/tst-ptrace-singleblock.c b/sysdeps/unix/sysv/linux/s390/tst-ptrace-singleblock.c
> new file mode 100644
> index 0000000..b384562
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/s390/tst-ptrace-singleblock.c
> @@ -0,0 +1,110 @@
> +/* Testing s390x PTRACE_SINGLEBLOCK ptrace request.
> +   Copyright (C) 2017 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <sys/wait.h>
> +#include <sys/types.h>
> +#include <support/xunistd.h>
> +
> +/* Ensure that we use the PTRACE_SINGLEBLOCK definition from glibc ptrace.h
> +   in tracer_func.  We need the kernel ptrace.h for structs ptrace_area
> +   and gregset_t.  */
> +#include <sys/ptrace.h>
> +static const enum __ptrace_request req_singleblock = PTRACE_SINGLEBLOCK;
> +#include <asm/ptrace.h>
> +
> +static void
> +tracee_func (int pid)
> +{
> +  /* Dump the mapping information for manual inspection of the printed
> +     tracee addresses.  */
> +  char str[80];
> +  sprintf (str, "cat /proc/%d/maps", pid);
> +  puts (str);
> +  system (str);
> +  fflush (stdout);
> +
> +  ptrace (PTRACE_TRACEME);
> +  /* Stop tracee.  Afterwards the tracer_func can operate.  */
> +  kill (pid, SIGSTOP);
> +
> +  puts ("The PTRACE_SINGLEBLOCK of the tracer will stop after: "
> +	"brasl %r14,<puts@plt>!");
> +}
> +
> +static void
> +tracer_func (int pid)
> +{
> +  unsigned long last_break;
> +  ptrace_area parea;
> +  gregset_t regs;
> +  int status;
> +
> +  while (1)
> +    {
> +      /* Wait for the tracee to be stopped or exited.  */
> +      wait (&status);
> +      if (WIFEXITED (status))
> +	break;
> +
> +      /* Get information about tracee: gprs, last breaking address.  */
> +      parea.len = sizeof (regs);
> +      parea.process_addr = (unsigned long) &regs;
> +      parea.kernel_addr = 0;
> +      ptrace (PTRACE_PEEKUSR_AREA, pid, &parea);

Note that you can verify whether PTRACE_PEEKUSR_AREA has returned
the expected result by comparing registers with those returned
by PTRACE_GETREGSET.  The latter is implemented on s390 since
linux 2.6.27 so its use in glibc is safe.

> +      ptrace (PTRACE_GET_LAST_BREAK, pid, NULL, &last_break);

As these ptrace calls are expected to succeed,
you might want to check their return code.

> +
> +      printf ("child IA: %p last_break: %p\n",
> +	      (void *) regs[1], (void *) last_break);
> +
> +      /* Execute tracee until next taken branch.
> +
> +	 Note:
> +	 Before the commit which introduced this testcase,
> +	 <glibc>/sysdeps/unix/sysv/linux/s390/sys/ptrace.h
> +	 uses ptrace-request 12 for PTRACE_GETREGS,
> +	 but <kernel>/include/uapi/linux/ptrace.h
> +	 uses 12 for PTRACE_SINGLEBLOCK.
> +
> +	 The s390 kernel has no support for PTRACE_GETREGS!
> +	 Thus glibc ptrace.h is adjusted to match kernel ptrace.h.
> +
> +	 This test ensures, that PTRACE_SINGLEBLOCK defined in glibc
> +	 works as expected.  If the kernel would interpret it as
> +	 PTRACE_GETREGS, then the tracee will not make any progress
> +	 and this testcase will time out.  */
> +      ptrace (req_singleblock, pid, NULL, NULL);

Likewise.


-- 
ldv

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