Re: [Qemu-devel] [PATCH RFC 1/4] log: Clean up misuse of Range for -dfilter

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 15, 2016 at 10:41:47PM +0200, Markus Armbruster wrote:
> Range encodes an integer interval [a,b] as { begin = a, end = b + 1 },
> where a \in [0,2^64-1] and b \in [1,2^64].  Thus, zero end is to be
> interpreted as 2^64.
> 
> The implementation of -dfilter (commit 3514552) uses Range
> differently: it encodes [a,b] as { begin = a, end = b }.  The code
> works, but it contradicts the specification of Range in range.h.
> 
> Switch to the specified representation.  Since it can't represent
> [0,UINT64_MAX], we have to reject that now.  Add a test for it.
> 
> While we're rejecting anyway: observe that we reject -dfilter LOB..UPB
> where LOB > UPB when UPB is zero, but happily create an empty Range
> when it isn't.  Reject it then, too, and add a test for it.
> 
> While there, add a positive test for the problematic upper bound
> UINT64_MAX.
> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  tests/test-logging.c | 10 ++++++++++
>  util/log.c           | 28 +++++++++++++++-------------
>  2 files changed, 25 insertions(+), 13 deletions(-)
> 
> diff --git a/tests/test-logging.c b/tests/test-logging.c
> index 440e75f..b6fa94e 100644
> --- a/tests/test-logging.c
> +++ b/tests/test-logging.c
> @@ -68,6 +68,16 @@ static void test_parse_range(void)
>      g_assert(qemu_log_in_addr_range(0x2050));
>      g_assert(qemu_log_in_addr_range(0x3050));
>  
> +    qemu_set_dfilter_ranges("0xffffffffffffffff-1", &error_abort);
> +    g_assert(qemu_log_in_addr_range(UINT64_MAX));
> +    g_assert_false(qemu_log_in_addr_range(UINT64_MAX - 1));
> +
> +    qemu_set_dfilter_ranges("0..0xffffffffffffffff", &err);
> +    error_free_or_abort(&err);
> +
> +    qemu_set_dfilter_ranges("2..1", &err);
> +    error_free_or_abort(&err);
> +
>      qemu_set_dfilter_ranges("0x1000+onehundred", &err);
>      error_free_or_abort(&err);
>  
> diff --git a/util/log.c b/util/log.c
> index 32e4160..f811d61 100644
> --- a/util/log.c
> +++ b/util/log.c
> @@ -131,8 +131,8 @@ bool qemu_log_in_addr_range(uint64_t addr)
>      if (debug_regions) {
>          int i = 0;
>          for (i = 0; i < debug_regions->len; i++) {
> -            struct Range *range = &g_array_index(debug_regions, Range, i);
> -            if (addr >= range->begin && addr <= range->end) {
> +            Range *range = &g_array_index(debug_regions, Range, i);
> +            if (addr >= range->begin && addr <= range->end - 1) {
>                  return true;
>              }
>          }
> @@ -158,7 +158,7 @@ void qemu_set_dfilter_ranges(const char *filter_spec, Error **errp)
>      for (i = 0; ranges[i]; i++) {
>          const char *r = ranges[i];
>          const char *range_op, *r2, *e;
> -        uint64_t r1val, r2val;
> +        uint64_t r1val, r2val, lob, upb;
>          struct Range range;
>  
>          range_op = strstr(r, "-");
> @@ -187,27 +187,29 @@ void qemu_set_dfilter_ranges(const char *filter_spec, Error **errp)
>                         (int)(r2 - range_op), range_op);
>              goto out;
>          }
> -        if (r2val == 0) {
> -            error_setg(errp, "Invalid range");
> -            goto out;
> -        }
>  
>          switch (*range_op) {
>          case '+':
> -            range.begin = r1val;
> -            range.end = r1val + (r2val - 1);
> +            lob = r1val;
> +            upb = r1val + r2val - 1;
>              break;
>          case '-':
> -            range.end = r1val;
> -            range.begin = r1val - (r2val - 1);
> +            upb = r1val;
> +            lob = r1val - (r2val - 1);
>              break;
>          case '.':
> -            range.begin = r1val;
> -            range.end = r2val;
> +            lob = r1val;
> +            upb = r2val;
>              break;
>          default:
>              g_assert_not_reached();
>          }
> +        if (lob > upb || (lob == 0 && upb == UINT64_MAX)) {
> +            error_setg(errp, "Invalid range");
> +            goto out;
> +        }
> +        range.begin = lob;
> +        range.end = upb + 1;
>          g_array_append_val(debug_regions, range);
>      }
>  out:
> -- 
> 2.5.5