From: "H. Peter Anvin" <hpa@zytor.com>
To: Philipp Kohlbecher <pk031698@uni-greifswald.de>
Cc: Dave Jones <davej@codemonkey.org.uk>,
Arnd Bergmann <arnd@arndb.de>,
linux-kernel@vger.kernel.org, linux-assembly@vger.kernel.org
Subject: Re: [PATCH 2.6.21.1] i386: save registers before intra-privilege syscall
Date: Thu, 17 May 2007 15:16:42 -0700 [thread overview]
Message-ID: <464CD44A.5000307@zytor.com> (raw)
In-Reply-To: <20070517220638.GA6532@localhost.localdomain>
Philipp Kohlbecher wrote:
> From: Philipp Kohlbecher <pk031698@uni-greifswald.de>
>
> The kernel_execve function issues a software interrupt (int 0x80) to make
> a system call to sys_execve. This function expects to find the stack segment
> and stack pointer of the function that issued the system call in the pt_regs
> struct. The syscall entry code that sets up this struct expects the stack
> segment and the stack pointer of the issuing function already on the stack.
> But the Intel processor saves these registers only if a stack-switch occurs,
> i.e. for inter-privilege interrupts and exceptions (cf. Intel Software
> Developer’s Manual, Vol. 3A, p. 5-17,
> http://www.intel.com/design/processor/manuals/253668.pdf).
> For an intra-privilege interrupt like the one issued in kernel_execve, these
> registers must be saved manually.
>
Could you describe the failure scenario this causes? I'm trying to
understand how something that fundamental would have possibly slipped by
testing?
-hpa
next prev parent reply other threads:[~2007-05-17 22:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-17 22:06 [PATCH 2.6.21.1] i386: save registers before intra-privilege syscall Philipp Kohlbecher
2007-05-17 22:16 ` H. Peter Anvin [this message]
2007-05-17 23:27 ` Philipp Kohlbecher
2007-05-17 23:33 ` H. Peter Anvin
2007-05-18 8:32 ` Philipp Kohlbecher
2007-05-18 22:41 ` H. Peter Anvin
2007-05-18 23:08 ` H. Peter Anvin
2007-05-21 10:48 ` Philipp Kohlbecher
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