| Message ID | 20180523031805.27101-2-peterx@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | error-report: introduce {error|warn}_report_once | expand |
On 05/22/2018 10:18 PM, Peter Xu wrote: > I stole the printk_once() macro. > > I always wanted to be able to print some error directly if there is a > buffer to dump, however we can't use error_report() where the code path > can be triggered by DDOS attack. To avoid that, we can introduce a > print-once-like function for it. Meanwhile, we also introduce the > corresponding helper for warn_report(). > > CC: Markus Armbruster <armbru@redhat.com> > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > include/qemu/error-report.h | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h > index e1c8ae1a52..3e6e84801f 100644 > --- a/include/qemu/error-report.h > +++ b/include/qemu/error-report.h > @@ -44,6 +44,32 @@ void error_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2); > void warn_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2); > void info_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2); > > +/* Similar to error_report(), but it only prints the message once. */ > +#define error_report_once(fmt, ...) \ > + ({ \ > + static bool __print_once; \ > + bool __ret_print_once = !__print_once; \ In v1 you were asked to avoid leading double underscore (https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg03442.html; use things like 'print_once_' instead) and to document the return value of these macros (https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg03503.html; having the return value makes it possible to write conditional code that caches further information about a first, but not repeat, failures). Why hasn't that happened?
diff --git a/include/qemu/error-report.h b/include/qemu/error-report.h index e1c8ae1a52..3e6e84801f 100644 --- a/include/qemu/error-report.h +++ b/include/qemu/error-report.h @@ -44,6 +44,32 @@ void error_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2); void warn_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2); void info_report(const char *fmt, ...) GCC_FMT_ATTR(1, 2); +/* Similar to error_report(), but it only prints the message once. */ +#define error_report_once(fmt, ...) \ + ({ \ + static bool __print_once; \ + bool __ret_print_once = !__print_once; \ + \ + if (!__print_once) { \ + __print_once = true; \ + error_report(fmt, ##__VA_ARGS__); \ + } \ + unlikely(__ret_print_once); \ + }) + +/* Similar to warn_report(), but it only prints the message once. */ +#define warn_report_once(fmt, ...) \ + ({ \ + static bool __print_once; \ + bool __ret_print_once = !__print_once; \ + \ + if (!__print_once) { \ + __print_once = true; \ + warn_report(fmt, ##__VA_ARGS__); \ + } \ + unlikely(__ret_print_once); \ + }) + const char *error_get_progname(void); extern bool enable_timestamp_msg;
I stole the printk_once() macro. I always wanted to be able to print some error directly if there is a buffer to dump, however we can't use error_report() where the code path can be triggered by DDOS attack. To avoid that, we can introduce a print-once-like function for it. Meanwhile, we also introduce the corresponding helper for warn_report(). CC: Markus Armbruster <armbru@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> --- include/qemu/error-report.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+)