diff options
| author | Donggeun Yoo <donggeunyoo.kernel@gmail.com> | 2026-09-17 10:55:32 +0900 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2026-10-15 19:59:35 -0400 |
| commit | 443d23176812803d0fa182b8d05ef066a7b8271f (patch) | |
| tree | ef52883a8b01a5605b88d5bea098cf9e00067433 /kernel/trace | |
| parent | 289e2a775de434ccab2d107076bc78362ce288bd (diff) | |
tracing: Fix 64-bit and signed histogram fields on 32-bit kernels
DEFINE_HIST_FIELD_FN() reads a trace event field and widens it to the u64
the histogram uses as a key or a value:
type *addr = (type *)(event + hist_field->field->offset);
return (u64)(unsigned long)*addr;
unsigned long is 32 bits on a 32-bit kernel, so the intermediate cast
discards the upper half of a 64-bit field, and widens a signed field by
zero extension from 32 bits rather than sign extension from its own
width. Five of the eight instantiations are wrong there: s64, u64, s32,
s16 and s8.
The cast came in with commit 79e577cbce4c ("tracing: Support string type
key properly"), which also added hist_field_dynstring() and
hist_field_pstring(). Those convert a char * to u64 and do warn without
an unsigned long in between on 32-bit. DEFINE_HIST_FIELD_FN() converts an
integer and never a pointer, so it gains nothing from the cast and only
loses information.
Drop the intermediate cast and let the usual arithmetic conversions widen
*addr according to its own type. unsigned long is 64 bits on LP64, so the
two forms are identical there and 64-bit kernels are unaffected.
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260917015532.103081-1-donggeunyoo.kernel@gmail.com
Fixes: 79e577cbce4c ("tracing: Support string type key properly")
Reported-by: sashiko-bot@kernel.org
Closes: https://lore.kernel.org/all/20260914054614.82A9B1F000FF@smtp.kernel.org/
Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/trace_events_hist.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index c150e1130a5f..7d3bb7da4dd1 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -466,7 +466,7 @@ static u64 hist_field_unary_minus(struct hist_field *hist_field, { \ type *addr = (type *)(event + hist_field->field->offset); \ \ - return (u64)(unsigned long)*addr; \ + return (u64)*addr; \ } DEFINE_HIST_FIELD_FN(s64); |