From: Mark Kettenis <kettenis@chello.nl>
To: roland@redhat.com
Cc: gdb@sources.redhat.com
Subject: Re: gdb support for Linux vsyscall DSO
Date: Thu, 15 May 2003 21:26:00 -0000 [thread overview]
Message-ID: <200305152125.h4FLPhd8000430@elgar.kettenis.dyndns.org> (raw)
In-Reply-To: <200305130153.h4D1rGW23237@magilla.sf.frob.com> (message from Roland McGrath on Mon, 12 May 2003 18:53:16 -0700)
Date: Mon, 12 May 2003 18:53:16 -0700
From: Roland McGrath <roland@redhat.com>
> There is some special handling for signal trampolines in
> infrun.c:handle_inferior_event(). Beware! Dragons can still be found
> in that function. However, it seems the bit of code I'm talking about
> is there for targets that don't known how to properly unwind signal
> frames :-).
I only partly follow the code in that function, but it does look
like it wants to know whether it's in a signal frame. I get the
impression that "next" or "step" interrupted by a signal lets the
signal be handled and continues until the end of the source line
rather than doing a normal user stop for the signal, and that this
is considered desireable. So it must know.
I'm not really sure. The code I referred to seems to be written for
BSD-style signal trampolines, where the signal trampoline will call
the signal handler. The Linux kernel calls the signal trampoline
directly, so perhaps it doesn't need this code.
Having a DWARF2 extension to mark signal frames seems reasonable, and less
kludgey than matching symbol names. However, I wonder if there is in fact
a way to do it that won't confuse older libgcc's .eh_frame unwinding code.
If the `z' augmentation doesn't confuse older libgcc's, I don't see
why adding another augmentation would do so. But we should first
determine if we really need it before adding it.
> Restoring %eflags is certainly possible. Making GDB actually pop the
> signal trampoline frame should work
I only mentioned %eflags to pedantic because I caught myself about to say
"restore the exact state of the interrupted thread" and that wasn't
completely true. I don't anticipate gdb having any reason to want to roll
back a signal frame. (However, in the abstract it seems like the right
thing for the kernel unwind info to describe restoring %eflags if the
DWARF2 format can already represent that.)
Well, GDB will do exactly that when the user gives the "return"
command in a signal trampoline.
Mark
next prev parent reply other threads:[~2003-05-15 21:26 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-09 9:45 gdb/dwarf-frame.c Roland McGrath
2003-05-09 13:41 ` gdb/dwarf-frame.c Daniel Jacobowitz
2003-05-09 14:10 ` gdb/dwarf-frame.c Elena Zannoni
2003-05-09 14:56 ` NPTL thread support H. J. Lu
2003-05-09 15:44 ` Elena Zannoni
[not found] ` <20030509091522.A2960@lucon.org>
[not found] ` <16059.55278.841645.134311@localhost.redhat.com>
2003-05-11 20:46 ` H. J. Lu
2003-05-12 19:24 ` J. Johnston
2003-05-12 20:08 ` H. J. Lu
2003-05-12 20:15 ` David Carlton
2003-05-12 21:09 ` Andrew Cagney
2003-05-12 21:18 ` David Carlton
2003-05-12 21:23 ` Daniel Jacobowitz
2003-05-12 20:17 ` Elena Zannoni
2003-05-09 17:01 ` gdb/dwarf-frame.c Andrew Cagney
2003-05-09 17:08 ` gdb/dwarf-frame.c Elena Zannoni
2003-05-09 19:43 ` gdb/dwarf-frame.c Mark Kettenis
2003-05-09 21:19 ` gdb/dwarf-frame.c Roland McGrath
2003-05-09 21:48 ` gdb/dwarf-frame.c Elena Zannoni
2003-05-09 22:17 ` gdb/dwarf-frame.c Roland McGrath
2003-05-09 21:54 ` gdb/dwarf-frame.c Andrew Cagney
2003-05-09 21:58 ` gdb/dwarf-frame.c Daniel Jacobowitz
2003-05-09 22:18 ` gdb/dwarf-frame.c Roland McGrath
2003-05-09 22:28 ` gdb/dwarf-frame.c Andrew Cagney
2003-05-09 22:33 ` gdb/dwarf-frame.c Roland McGrath
2003-05-09 20:32 ` gdb/dwarf-frame.c Roland McGrath
2003-05-09 19:36 ` gdb/dwarf-frame.c Mark Kettenis
2003-05-09 21:34 ` gdb/dwarf-frame.c Roland McGrath
2003-05-09 21:46 ` gdb/dwarf-frame.c Elena Zannoni
2003-05-10 7:07 ` gdb support for Linux vsyscall DSO Roland McGrath
2003-05-10 17:24 ` Andrew Cagney
2003-05-10 18:13 ` Daniel Jacobowitz
2003-05-10 19:42 ` Roland McGrath
2003-05-10 21:49 ` Andrew Cagney
2003-05-12 19:23 ` Andrew Cagney
2003-05-13 2:29 ` Roland McGrath
2003-05-13 16:03 ` Andrew Cagney
2003-05-10 21:28 ` Roland McGrath
2003-05-10 17:55 ` Mark Kettenis
2003-05-10 20:27 ` Roland McGrath
2003-05-11 23:14 ` Mark Kettenis
2003-05-13 1:53 ` Roland McGrath
2003-05-15 21:26 ` Mark Kettenis [this message]
2003-05-16 2:25 ` Roland McGrath
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