From: Daniel Jacobowitz <drow@false.org>
To: Richard Earnshaw <rearnsha@arm.com>
Cc: Michael Snyder <msnyder@vmware.com>,
"Maciej W. Rozycki" <macro@codesourcery.com>,
"gdb-patches@sourceware.org" <gdb-patches@sourceware.org>
Subject: Re: [PING][PATCH] ARM/Linux: Unwind restart_syscall(2) frames
Date: Tue, 22 Dec 2009 16:17:00 -0000 [thread overview]
Message-ID: <20091222161747.GA3211@caradoc.them.org> (raw)
In-Reply-To: <1261495721.26179.67.camel@e200601-lin.cambridge.arm.com>
On Tue, Dec 22, 2009 at 03:28:41PM +0000, Richard Earnshaw wrote:
> It's not code that I'm familiar with, however...
>
> svc 0x00900000
> ldr pc, [sp], #12
> then
>
> + trad_frame_set_reg_value (this_cache, ARM_SP_REGNUM, sp + 12);
>
> So why is the stack pointer /incremented/ by 12 at this point (which
> deallocates stack) rather than decremented to compensate for the
> increment that will follow? Also, shouldn't the stack allocation be a
> multiple of 8 to fully conform to the ABI stack alignment constraints?
We're before execution of the above trampoline at this point, trying
to compensate for it; that's why the stack goes up, we're simulating
return from the trampoline. The code sequence was chosen by the
kernel, weird stack alignment and all.
--
Daniel Jacobowitz
CodeSourcery
prev parent reply other threads:[~2009-12-22 16:17 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-18 14:13 Maciej W. Rozycki
2009-12-18 19:35 ` Michael Snyder
2009-12-22 15:28 ` Richard Earnshaw
2009-12-22 16:17 ` Daniel Jacobowitz [this message]
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