Subject: Re: ARM1136 panic on arm32_sync_icache()
To: Todd Poynor <>
From: Matt Thomas <>
List: port-arm
Date: 11/07/2007 19:49:09
On Nov 7, 2007, at 4:58 PM, Todd Poynor wrote:

> A program containing the following fragment can crash an ARM1136  
> system with a Data Abort in the kernel:
> 	struct arm_sync_icache_args a;
> 	a.addr = malloc(PAGE_SIZE * 3);
> 	a.len = PAGE_SIZE * 3;
> 	sysarch(ARM_SYNC_ICACHE, &a);
> The ARMv6 Virtually Indexed Physically Tagged cache maintenance  
> system control coprocessor instructions that invalidate lines based  
> on Modified Virtual Addresses throw Data Abort exceptions for  
> virtual addresses not mapped in the PTE.  On previous VIVT cache  
> revisions of the architecture, a PTE lookup was not necessary, and  
> so callers that synced cache lines in pages not actually written  
> did not incur this problem.
> One workaround is to have the syscall version invalidate the entire  
> cache (another popular UNIX variant does this a lot due to ARM1136  
> errata).  Or invalidate based on set/way (which at 4KB ways means  
> invalidating a whole lotta cache).  Or figure out the cause of the  
> kernel Data Abort and either send the process a SIGSEGV or skip  
> faulting instructions (or fix up address range and restart for MCRR  
> range instructions).
> I'll send a patch for one of those options if nobody raises any  
> objections or alternate suggestions.  Thanks,

I prefer the of onfault since this error shouldn't normally happen.