6.12-stable review patch. If anyone has any objections, please let me know.
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From: Stephen Brennan stephen.s.brennan@oracle.com
[ Upstream commit ebf0b332732dcc64239119e554faa946562b0b93 ]
Kernel modules for which we cannot find a file on-disk will have a dso->long_name that looks like "[module_name]". Prior to the commit listed in the fixes, the dso->kernel field would be zero (for user space), so dso__is_kallsyms() would return false. After the commit, kernel module DSOs are correctly labeled, but the result is that dso__is_kallsyms() erroneously returns true for those modules without a filesystem path.
Later, build_id_cache__add() consults this value of is_kallsyms, and when true, it copies /proc/kallsyms into the cache. Users with many kernel modules without a filesystem path (e.g. ksplice or possibly kernel live patch modules) have reported excessive disk space usage in the build ID cache directory due to this behavior.
To reproduce the issue, it's enough to build a trivial out-of-tree hello world kernel module, load it using insmod, and then use:
perf record -ag -- sleep 1
In the build ID directory, there will be a directory for your module name containing a kallsyms file.
Fix this up by changing dso__is_kallsyms() to consult the dso_binary_type enumeration, which is also symmetric to the above checks for dso__is_vmlinux() and dso__is_kcore(). With this change, kallsyms is not cached in the build-id cache for out-of-tree modules.
Fixes: 02213cec64bbe ("perf maps: Mark module DSOs with kernel type") Signed-off-by: Stephen Brennan stephen.s.brennan@oracle.com Link: https://lore.kernel.org/r/20250318230012.2038790-1-stephen.s.brennan@oracle.... Signed-off-by: Namhyung Kim namhyung@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/util/dso.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h index bb8e8f444054d..c0472a41147c3 100644 --- a/tools/perf/util/dso.h +++ b/tools/perf/util/dso.h @@ -808,7 +808,9 @@ static inline bool dso__is_kcore(const struct dso *dso)
static inline bool dso__is_kallsyms(const struct dso *dso) { - return RC_CHK_ACCESS(dso)->kernel && RC_CHK_ACCESS(dso)->long_name[0] != '/'; + enum dso_binary_type bt = dso__binary_type(dso); + + return bt == DSO_BINARY_TYPE__KALLSYMS || bt == DSO_BINARY_TYPE__GUEST_KALLSYMS; }
bool dso__is_object_file(const struct dso *dso);