linux-kernel - Re: [PATCH 2/3] kgdb,i386: use address that SP register points to in the exception frame

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Date:	Fri, 15 May 2009 08:16:26 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jason Wessel <jason.wessel@...driver.com>
cc:	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net
Subject: Re: [PATCH 2/3] kgdb,i386: use address that SP register points to
 in the exception frame



On Fri, 15 May 2009, Jason Wessel wrote:
>
> The treatment of the SP register is different on x86_64 and i386.
> This is a regression fix that lived outside the mainline kernel from
> 2.6.27 to now.  The regression was a result of the original merge
> consolidation of the i386 and x86_64 archs to x86.
> 
> The incorrectly reported SP on i386 prevented stack tracebacks from
> working correctly in gdb.

Is this only ever used for kernel register state?

Because in the _general_ case, the code should likely be something like

	if (user_mode_vm(regs)) {
		gdb_regs[GDB_SS] = regs->ss;
		gdb_regs[GDB_SP] = regs->sp;
	} else {
		gdb_regs[GDB_SS] = __KERNEL_DS;
		gdb_regs[GDB_SP] = (unsigned long)&regs->sp
	}

if the 'regs' contents can ever point to user mode state.

		Linus
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