6.12-stable review patch. If anyone has any objections, please let me know.
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From: Adrian Hunter adrian.hunter@intel.com
commit ebfc8542ad62d066771e46c8aa30f5624b89cad8 upstream.
It was reported that Intel PT address filters do not work in Docker containers. That relates to the use of overlayfs.
overlayfs records the backing file in struct vm_area_struct vm_file, instead of the user file that the user mmapped. In order for an address filter to match, it must compare to the user file inode. There is an existing helper file_user_inode() for that situation.
Use file_user_inode() instead of file_inode() to get the inode for address filter matching.
Example:
Setup:
# cd /root # mkdir test ; cd test ; mkdir lower upper work merged # cp `which cat` lower # mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merged # perf record --buildid-mmap -e intel_pt//u --filter 'filter * @ /root/test/merged/cat' -- /root/test/merged/cat /proc/self/maps ... 55d61d246000-55d61d2e1000 r-xp 00018000 00:1a 3418 /root/test/merged/cat ... [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.015 MB perf.data ] # perf buildid-cache --add /root/test/merged/cat
Before:
Address filter does not match so there are no control flow packets
# perf script --itrace=e # perf script --itrace=b | wc -l 0 # perf script -D | grep 'TIP.PGE' | wc -l 0 #
After:
Address filter does match so there are control flow packets
# perf script --itrace=e # perf script --itrace=b | wc -l 235 # perf script -D | grep 'TIP.PGE' | wc -l 57 #
With respect to stable kernels, overlayfs mmap function ovl_mmap() was added in v4.19 but file_user_inode() was not added until v6.8 and never back-ported to stable kernels. FMODE_BACKING that it depends on was added in v6.5. This issue has gone largely unnoticed, so back-porting before v6.8 is probably not worth it, so put 6.8 as the stable kernel prerequisite version, although in practice the next long term kernel is 6.12.
Closes: https://lore.kernel.org/linux-perf-users/aBCwoq7w8ohBRQCh@fremen.lan Reported-by: Edd Barrett edd@theunixzoo.co.uk Signed-off-by: Adrian Hunter adrian.hunter@intel.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Amir Goldstein amir73il@gmail.com Cc: stable@vger.kernel.org # 6.8 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/events/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9086,7 +9086,7 @@ static bool perf_addr_filter_match(struc if (!filter->path.dentry) return false;
- if (d_inode(filter->path.dentry) != file_inode(file)) + if (d_inode(filter->path.dentry) != file_user_inode(file)) return false;
if (filter->offset > offset + size)