Re: what is the right behavior of copy_to_user(0x0, ..., ...)?

[Jun Sun <jsun@mvista.com>]

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It would help if not for the gross typo. :-)  See the attachment.

Jun


Ralf Baechle wrote:

> On Fri, May 03, 2002 at 04:41:56PM -0700, Jun Sun wrote:
> 
> 
>>It appears earlier version of kernel does not have this problem.  I have not 
>>fully figured out why.
>>
> 
> We didn't handle exceptions in branch delay slots.  Try this patch and
> tell me if it helps.
> 
>   Ralf
> 
> Index: arch/mips/mm/fault.c
> ===================================================================
> RCS file: /home/pub/cvs/linux/arch/mips/mm/fault.c,v
> retrieving revision 1.25.2.2
> diff -u -r1.25.2.2 fault.c
> --- arch/mips/mm/fault.c	16 Jan 2002 03:49:24 -0000	1.25.2.2
> +++ arch/mips/mm/fault.c	4 May 2002 01:28:34 -0000
> @@ -19,6 +19,7 @@
>  #include <linux/smp_lock.h>
>  #include <linux/version.h>
>  
> +#include <asm/branch.h>
>  #include <asm/hardirq.h>
>  #include <asm/pgalloc.h>
>  #include <asm/mmu_context.h>
> @@ -77,7 +78,7 @@
>  	struct vm_area_struct * vma;
>  	struct task_struct *tsk = current;
>  	struct mm_struct *mm = tsk->mm;
> -	unsigned long fixup;
> +	unsigned long epc, fixup;
>  	siginfo_t info;
>  
>  	/*
> @@ -181,7 +182,8 @@
>  
>  no_context:
>  	/* Are we prepared to handle this kernel fault?  */
> -	fixup = search_exception_table(regs->cp0_epc);
> +	epc = regs->cp0_epc + delay_slot(regs) ? 4 : 0;
> +	fixup = search_exception_table(epc);
>  	if (fixup) {
>  		long new_epc;
>  
> Index: arch/mips64/mm/fault.c
> ===================================================================
> RCS file: /home/pub/cvs/linux/arch/mips64/mm/fault.c,v
> retrieving revision 1.26.2.6
> diff -u -r1.26.2.6 fault.c
> --- arch/mips64/mm/fault.c	23 Feb 2002 02:16:42 -0000	1.26.2.6
> +++ arch/mips64/mm/fault.c	4 May 2002 01:28:34 -0000
> @@ -21,6 +21,7 @@
>  #include <linux/smp_lock.h>
>  #include <linux/version.h>
>  
> +#include <asm/branch.h>
>  #include <asm/hardirq.h>
>  #include <asm/pgalloc.h>
>  #include <asm/mmu_context.h>
> @@ -103,7 +104,7 @@
>  	struct vm_area_struct * vma;
>  	struct task_struct *tsk = current;
>  	struct mm_struct *mm = tsk->mm;
> -	unsigned long fixup;
> +	unsigned long epc, fixup;
>  	siginfo_t info;
>  
>  #if 0
> @@ -208,7 +209,8 @@
>  
>  no_context:
>  	/* Are we prepared to handle this kernel fault?  */
> -	fixup = search_exception_table(regs->cp0_epc);
> +	epc = regs->cp0_epc + delay_slot(regs) ? 4 : 0;
> +	fixup = search_exception_table(epc);
>  	if (fixup) {
>  		long new_epc;
>  
> 


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diff -Nru link/arch/mips/mm/fault.c.orig link/arch/mips/mm/fault.c
--- link/arch/mips/mm/fault.c.orig	Mon May  6 11:12:41 2002
+++ link/arch/mips/mm/fault.c	Mon May  6 11:15:12 2002
@@ -182,7 +182,7 @@
 
 no_context:
 	/* Are we prepared to handle this kernel fault?  */
-	epc = regs->cp0_epc + delay_slot(regs) ? 4 : 0;
+	epc = regs->cp0_epc + (delay_slot(regs) ? 4 : 0);
 	fixup = search_exception_table(epc);
 	if (fixup) {
 		long new_epc;
diff -Nru link/arch/mips64/mm/fault.c.orig link/arch/mips64/mm/fault.c
--- link/arch/mips64/mm/fault.c.orig	Mon May  6 11:12:44 2002
+++ link/arch/mips64/mm/fault.c	Mon May  6 11:15:26 2002
@@ -209,7 +209,7 @@
 
 no_context:
 	/* Are we prepared to handle this kernel fault?  */
-	epc = regs->cp0_epc + delay_slot(regs) ? 4 : 0;
+	epc = regs->cp0_epc + (delay_slot(regs) ? 4 : 0);
 	fixup = search_exception_table(epc);
 	if (fixup) {
 		long new_epc;