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From: "vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug tdep/31071] [gdb/tdep, arm] FAIL: gdb.base/catch-syscall.exp:
 execve: syscall execve has returned
Date: Thu, 16 Nov 2023 09:49:44 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D31071

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
Note the special execve handling in aarch64_linux_get_syscall_number:
...
  /* On exit from a successful execve, we will be in a new process and all =
the=20=20
     registers will be cleared - x0 to x30 will be 0, except for a 1 in x7.=
=20=20=20=20=20
     This function will only ever get called when stopped at the entry or e=
xit=20=20
     of a syscall, so by checking for 0 in x0 (arg0/retval), x1 (arg1), x8=
=20=20=20=20=20=20
     (syscall), x29 (FP) and x30 (LR) we can infer:=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
     1) Either inferior is at exit from successful execve.=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
     2) Or inferior is at entry to a call to io_setup with invalid arguments
and=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
        a corrupted FP and LR.=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20
     It should be safe enough to assume case 1.  */
  if (ret =3D=3D 0)
    {
      LONGEST x1 =3D -1, fp =3D -1, lr =3D -1;
      regs->cooked_read (AARCH64_X0_REGNUM + 1, &x1);
      regs->cooked_read (AARCH64_FP_REGNUM, &fp);
      regs->cooked_read (AARCH64_LR_REGNUM, &lr);
      if (x1 =3D=3D 0 && fp =3D=3D0 && lr =3D=3D 0)
        return aarch64_sys_execve;
    }
...

--=20
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