+ Evgenii, Kostya for KASAN On Tue, Feb 19, 2019 at 2:17 PM Qian Cai <cai@xxxxxx> wrote: > > On Tue, 2019-02-19 at 22:49 +0100, Arnd Bergmann wrote: > > Building an arm64 allmodconfig kernel with clang results in over 140 warnings > > about overly large stack frames, the worst ones being: > > > > drivers/gpu/drm/panel/panel-sitronix-st7789v.c:196:12: error: stack frame size > > of 20224 bytes in function 'st7789v_prepare' > > drivers/video/fbdev/omap2/omapfb/displays/panel-tpo-td028ttec1.c:196:12: > > error: stack frame size of 13120 bytes in function 'td028ttec1_panel_enable' > > drivers/usb/host/max3421-hcd.c:1395:1: error: stack frame size of 10048 bytes > > in function 'max3421_spi_thread' > > drivers/net/wan/slic_ds26522.c:209:12: error: stack frame size of 9664 bytes > > in function 'slic_ds26522_probe' > > drivers/crypto/ccp/ccp-ops.c:2434:5: error: stack frame size of 8832 bytes in > > function 'ccp_run_cmd' > > drivers/media/dvb-frontends/stv0367.c:1005:12: error: stack frame size of 7840 > > bytes in function 'stv0367ter_algo' > > > > None of these happen with gcc today, and almost all of these are the result > > of a single known bug in llvm. Hopefully it will eventually get fixed with > > the > > clang-9 release. Would it be better to disable outright if CC_IS_CLANG, then go back and adjust it once we know explicitly which version it lands in? (Maybe I'm being too pessimistic about when it may be fixed). > > > > In the meantime, the best idea I have is to turn off asan-stack for clang-8 > > and earlier, so we can produce a kernel that is safe to run. > > > > I have posted three patches that address the frame overflow warnings that are > > not addressed by turning off asan-stack, so in combination with this change, > > we get much closer to a clean allmodconfig build, which in turn is necessary > > to do meaningful build regression testing. > > Well, I am using clang 8.0 on arm64 and running the kernel just fine for a few > weeks now and never trigger a single stack overflow (THREAD_SHIFT = 15) because > I never use any of those drivers you mentioned above. I don't think it is a good > idea to blankly remove the testing coverage here and affect people don't use all > those offensive functions at all. Thanks for the patch, Arnd! Hopefully we can fix that up in Clang soon. Qian, I guess the alternative would be to add `-mllvm -asan-stack=0` on potentially up to 140 Makefiles? -- Thanks, ~Nick Desaulniers
