Messages in this thread | | | Date | Thu, 17 May 2007 15:16:42 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 2.6.21.1] i386: save registers before intra-privilege syscall |
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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?
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