On 14/02/2025 16:34, Andrew Cooper wrote: > Hello, > > I think this is a new feature request. > > I'm tracking down a UBSAN failure (only shows up on one arch, and it's > in a list_for_each() so there's loads of container_of() going on too). > > Newer versions of pahole have the overall structure alignment given the > end, but I can't seem to persuade it to give the the alignment of each > field. > > More concretely, I'm looking at a structure which is nearly 4k in size, > differs per arch and has an overall alignment of 128, but I can't find > which sub-struct within it is causing such an alignment requirement. > > Would it be possible to also print the alignment information in the > comments that exist already? i.e., instead of: > > /* $offset $size */ > > could we have > > /* $offset $size $align */ > > ? > hi Andrew, I might be missing something but I think "pahole -E <struct_name>" should give what you're looking for. This should show any nested structs which have alignment attributes associated. For example with "pahole -E task_struct" I see the a few substructures tagged with alignment attributes: $ pahole -E task_struct|grep align } avg __attribute__((__aligned__(64))); /* 320 64 */ } __attribute__((__aligned__(64))) stats __attribute__((__aligned__(64))); /* 960 256 */ /* Force alignment to the next boundary: */ } regs __attribute__((__aligned__(64))); /* 6016 4096 */ } fpu __attribute__((__aligned__(64))); /* 5888 4224 */ } thread __attribute__((__aligned__(64))); /* 5696 4416 */ /* forced alignments: 2, forced holes: 2, sum forced holes: 88 */ It's possible there are bugs that mean this doesn't always work correctly of course; it would be worth trying if that helps and if you run into any issues let us know. Thanks! Alan
