[PATCH] lib: fwts_safe_mem: add SIGBUS handling

[Erico Nunes]

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>