On Sat, Jan 16, 2021 at 2:59 AM Eric Biggers <ebiggers@xxxxxxxxxx> wrote: > On Sat, Jan 16, 2021 at 08:59:50AM +0800, kernel test robot wrote > > Looks like the clang bug that causes large stack usage in this function > (https://bugs.llvm.org/show_bug.cgi?id=45803 which is still unfixed) got > triggered again. Note that the function only has 264 bytes of local variables, > so there's no reason why it should use anywhere near 9776 bytes of stack space. > > I'm not sure what we can do about this. Last time the solution was commit > 0c0408e86dbe which randomly added a 'pragma nounroll' to the loop at the end. > > Anyone have any better idea than randomly trying adding optimization pragmas and > seeing what makes the report go away? > > Also this was reported with clang 12.0.0 which is a prerelease version, so I'm > not sure how much I'm supposed to care about this report. I sent a workaround to disable UBSAN_UNSIGNED_OVERFLOW an x86-32, after showing that this did not affect arm32, arm64 or x86-64: 27c287b41659 ("ubsan: disable unsigned-overflow check for i386") As the report is for ppc64, it appears that this is not just specific to x86-32 after all. I have had no success in isolating the problem in clang, but I did not try too hard either. I see this .config also enables CONFIG_UBSAN_UNSIGNED_OVERFLOW=y, so it would be a reasonable assumption that this is the same problem as on x86-32. There is also another thread on CONFIG_UBSAN_UNSIGNED_OVERFLOW causing BUILD_BUG_ON() failures. Arnd
