On Sat, Feb 25, 2017 at 10:18:23AM +0100, Ingo Molnar wrote:
> > Sadly this only works for WARN_ON_ONCE(), since the others have
> > printk() statements prior to triggering the trap.
>
> Which one is problematic to convert, WARN_ONCE()?
Yes, WARN_ONCE(), all the ones that have printf fmt crud in.
If we want report_bug() to do the _ONCE thing, we also need that to do
the printk().
I tried the below hackery (beware eye and brain damage ahead) which
actually compiles, but generates horrific junk -- far larger than
without.
The __builtin_va_*() crud was really not meant for things like this.
---
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -66,6 +66,11 @@ do {
\
#define __WARN_FLAGS(flags) _BUG_FLAGS(ASM_UD0, BUGFLAG_WARNING|(flags))
+#define __WARN_ARGS_FLAGS(args, flags) do { \
+ asm volatile ("" : : "a" (args)); \
+ _BUG_FLAGS(ASM_UD0, BUGFLAG_WARNING|(flags)); \
+} while (0)
+
#include <asm-generic/bug.h>
#endif /* _ASM_X86_BUG_H */
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -7,6 +7,7 @@
#define BUGFLAG_WARNING (1 << 0)
#define BUGFLAG_ONCE (1 << 1)
#define BUGFLAG_DONE (1 << 2)
+#define BUGFLAG_ARGS (1 << 3)
#define BUGFLAG_TAINT(taint) (BUGFLAG_WARNING | ((taint) << 8))
#define BUG_GET_TAINT(bug) ((bug)->flags >> 8)
#endif
@@ -67,8 +68,28 @@ struct bug_entry {
__WARN_ONCE_TAINT(TAINT_WARN); \
unlikely(__ret_warn_on); \
})
+
+#ifdef __WARN_ARGS_FLAGS
+static inline void __va_hack(va_list *ap, ...)
+{
+ va_start(*ap, ap);
+}
+
+#define __WARN_printf(arg...) do { \
+ va_list __ap; \
+ __va_hack(&__ap, arg); \
+ __WARN_ARGS_FLAGS(&__ap, BUGFLAG_ARGS|BUGFLAG_TAINT(TAINT_WARN));
\
+} while (0)
+
+#define __WARN_printf_taint(taint, arg...) do {
\
+ va_list __ap; \
+ __va_hack(&__ap, arg); \
+ __WARN_ARGS_FLAGS(&__ap, BUGFLAG_ARGS|BUGFLAG_TAINT(taint)); \
+} while (0)
#endif
+#endif /* __WARN_FLAGS */
+
/*
* WARN(), WARN_ON(), WARN_ON_ONCE, and so on can be used to report
* significant issues that need prompt attention if they should ever
@@ -90,10 +111,12 @@ extern void warn_slowpath_null(const cha
warn_slowpath_fmt_taint(__FILE__, __LINE__, taint, arg)
#else
#define __WARN() __WARN_TAINT(TAINT_WARN)
+#ifndef __WARN_ARGS_FLAGS
#define __WARN_printf(arg...) do { printk(arg); __WARN(); } while (0)
#define __WARN_printf_taint(taint, arg...) \
do { printk(arg); __WARN_TAINT(taint); } while (0)
#endif
+#endif
/* used internally by panic.c */
struct warn_args;
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -143,7 +143,8 @@ enum bug_trap_type report_bug(unsigned l
{
struct bug_entry *bug;
const char *file;
- unsigned line, warning, once, done;
+ unsigned line, warning, once, done, args;
+ va_list *ap;
if (!is_valid_bugaddr(bugaddr))
return BUG_TRAP_TYPE_NONE;
@@ -166,6 +167,7 @@ enum bug_trap_type report_bug(unsigned l
warning = (bug->flags & BUGFLAG_WARNING) != 0;
once = (bug->flags & BUGFLAG_ONCE) != 0;
done = (bug->flags & BUGFLAG_DONE) != 0;
+ args = (bug->flags & BUGFLAG_ARGS) != 0;
if (warning && once) {
if (done)
@@ -176,9 +178,16 @@ enum bug_trap_type report_bug(unsigned l
*/
bug->flags |= BUGFLAG_DONE;
}
+
+ if (args)
+ ap = (va_list *)regs->ax;
}
if (warning) {
+ if (args) {
+ const char *fmt = va_arg(*ap, const char *);
+ vprintk(fmt, *ap);
+ }
/* this is a WARN_ON rather than BUG/BUG_ON */
__warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs,
NULL);
