[PATCH] lib: fwts_safe_mem: add SIGBUS handling

[Colin Ian King]

On 06/06/17 13:07, Erico Nunes wrote:
> On 06/05/2017 04:15 PM, Colin King wrote:
>> From: Colin Ian King <colin.king at canonical.com>
>>
>> We should also add SIGBUS protection on unsafe memory reads; we're
>> seeing these occur on ARM64 platforms and we don't want fwts to break
>> because of SIGBUS crashes.
>>
>> Signed-off-by: Colin Ian King <colin.king at canonical.com>
>> ---
>>  src/lib/src/fwts_safe_mem.c | 18 +++++++++++-------
>>  1 file changed, 11 insertions(+), 7 deletions(-)
>>
>> diff --git a/src/lib/src/fwts_safe_mem.c b/src/lib/src/fwts_safe_mem.c
>> index fe71d5a8..a25d389a 100644
>> --- a/src/lib/src/fwts_safe_mem.c
>> +++ b/src/lib/src/fwts_safe_mem.c
>> @@ -23,18 +23,19 @@
>>  #include "fwts.h"
>>  
>>  static sigjmp_buf jmpbuf;
>> -static struct sigaction old_action;
>> +static struct sigaction old_segv_action, old_bus_action;
>>  
>>  /*
>> - *  If we hit a SIGSEGV then the port read
>> + *  If we hit a SIGSEGV or SIGBUS then the read
>>   *  failed and we longjmp back and return
>>   *  FWTS_ERROR
>>   */
>> -static void segv_handler(int dummy)
>> +static void sig_handler(int dummy)
>>  {
>>  	FWTS_UNUSED(dummy);
>>  
>> -	fwts_sig_handler_restore(SIGSEGV, &old_action);
>> +	fwts_sig_handler_restore(SIGSEGV, &old_segv_action);
>> +	fwts_sig_handler_restore(SIGBUS, &old_bus_action);
>>  	siglongjmp(jmpbuf, 1);
>>  }
>>  
>> @@ -42,16 +43,19 @@ static void segv_handler(int dummy)
>>   *  fwts_safe_memcpy()
>>   *	memcpy that catches segfaults. to be used when
>>   *	attempting to read BIOS tables from memory which
>> - *	may segfault if the src address is corrupt
>> + *	may segfault or throw a bus error if the src
>> + *	address is corrupt
>>   */
>>  int fwts_safe_memcpy(void *dst, const void *src, const size_t n)
>>  {
>>  	if (sigsetjmp(jmpbuf, 1) != 0)
>>  		return FWTS_ERROR;
>>  	
>> -	fwts_sig_handler_set(SIGSEGV, segv_handler, &old_action);
>> +	fwts_sig_handler_set(SIGSEGV, sig_handler, &old_segv_action);
>> +	fwts_sig_handler_set(SIGBUS, sig_handler, &old_bus_action);
>>  	memcpy(dst, src, n);
>> -	fwts_sig_handler_restore(SIGSEGV, &old_action);
>> +	fwts_sig_handler_restore(SIGSEGV, &old_segv_action);
>> +	fwts_sig_handler_restore(SIGBUS, &old_bus_action);
>>  
>>  	return FWTS_OK;
>>  }
>>
> 
> Thanks for the patch, I have tested it in my target and it does prevent
> the crash from happening.
> 
> Acked-by: Erico Nunes <nunes.erico at gmail.com>
> Tested-by: Erico Nunes <nunes.erico at gmail.com>
> 
Thanks for the positive feedback!

Colin