Commit 869f96a0 authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds
Browse files

[PATCH] x86: compress the stack layout of do_page_fault() 



This patch pushes the creation of a rare signal frame (SIGBUS or SIGSEGV)
into a separate function, thus saving stackspace in the main
do_page_fault() stackframe.  The effect is 132 bytes less of stack used by
the typical do_page_fault() invocation - resulting in a denser
cache-layout.

(Another minor effect is that in case of kernel crashes that come from a
pagefault, we add less space to the already existing frame, giving the
crash functions a slightly higher chance to do their stuff without
overflowing the stack.)

(The changes also result in slightly cleaner code.)

argument bugfix from "Guillaume C." <guichaz@gmail.com>

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7e06066b

arch/i386/mm/fault.c

+17 −14
Original line number Diff line number Diff line
@@ -199,6 +199,18 @@ static inline int is_prefetch(struct pt_regs *regs, unsigned long addr, 
	return 0;

} 



static noinline void force_sig_info_fault(int si_signo, int si_code,

	unsigned long address, struct task_struct *tsk)

{

	siginfo_t info;



	info.si_signo = si_signo;

	info.si_errno = 0;

	info.si_code = si_code;

	info.si_addr = (void __user *)address;

	force_sig_info(si_signo, &info, tsk);

}



fastcall void do_invalid_op(struct pt_regs *, unsigned long);



/*
@@ -218,8 +230,7 @@ fastcall void do_page_fault(struct pt_regs *regs, unsigned long error_code) 
	struct vm_area_struct * vma;

	unsigned long address;

	unsigned long page;

	int write;

	siginfo_t info;

	int write, si_code;



	/* get the address */

	__asm__("movl %%cr2,%0":"=r" (address));
@@ -233,7 +244,7 @@ fastcall void do_page_fault(struct pt_regs *regs, unsigned long error_code) 


	tsk = current;



	info.si_code = SEGV_MAPERR;

	si_code = SEGV_MAPERR;



	/*

	 * We fault-in kernel-space virtual memory on-demand. The
@@ -313,7 +324,7 @@ fastcall void do_page_fault(struct pt_regs *regs, unsigned long error_code) 
 * we can handle it..

 */

good_area:

	info.si_code = SEGV_ACCERR;

	si_code = SEGV_ACCERR;

	write = 0;

	switch (error_code & 3) {

		default:	/* 3: write, present */
@@ -387,11 +398,7 @@ bad_area_nosemaphore: 
		/* Kernel addresses are always protection faults */

		tsk->thread.error_code = error_code | (address >= TASK_SIZE);

		tsk->thread.trap_no = 14;

		info.si_signo = SIGSEGV;

		info.si_errno = 0;

		/* info.si_code has been set above */

		info.si_addr = (void __user *)address;

		force_sig_info(SIGSEGV, &info, tsk);

		force_sig_info_fault(SIGSEGV, si_code, address, tsk);

		return;

	}
@@ -500,11 +507,7 @@ do_sigbus: 
	tsk->thread.cr2 = address;

	tsk->thread.error_code = error_code;

	tsk->thread.trap_no = 14;

	info.si_signo = SIGBUS;

	info.si_errno = 0;

	info.si_code = BUS_ADRERR;

	info.si_addr = (void __user *)address;

	force_sig_info(SIGBUS, &info, tsk);

	force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);

	return;



vmalloc_fault:

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