On Wed, Feb 20, 2019 at 7:44 AM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > > On Wed, Feb 20, 2019 at 1:34 AM Kostya Serebryany <kcc@xxxxxxxxxx> wrote: > > > > On Tue, Feb 19, 2019 at 2:43 PM Nick Desaulniers > > <ndesaulniers@xxxxxxxxxx> wrote: > > > > > > + 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. > > > > I am not confident we can fix this in clang. > > The difference between gcc and clang, AFAICT, is not in the asan > > instrumentation, but in inining. > > Looking at the reproducer from https://bugs.llvm.org/show_bug.cgi?id=38809#c4, > > if I change ltv350qv_write_reg to always inline, gcc also produces a > > huge 10K stack frame, > > and making it noinline fixes the stack frame for both gcc and clang. > > Does your gcc have fix for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 ? > > For me gcc rejects to inline it: > > gcc version 7.3.0 (Debian 7.3.0-5) > > $ gcc /tmp/test.c -Wframe-larger-than=128 -c -fsanitize=kernel-address > -O2 --param asan-stack=1 > /tmp/test.c:23:13: warning: always_inline function might not be > inlinable [-Wattributes] I don't see that warning here > static void ltv350qv_write_reg(void) { > ^~~~~~~~~~~~~~~~~~ > /tmp/test.c: In function ‘ltv350qv_power_on’: > /tmp/test.c:57:1: warning: the frame size of 416 bytes is larger than > 128 bytes [-Wframe-larger-than=] > } but I also see the small stack size here: https://godbolt.org/z/Uz5Ruv gcc definitely inlines the function here but only has one copy of spi_message and spi_transfer on the stack, while clang inserts a call to __asan_report_store8_noabort() and has one copy per inlined call to ltv350qv_write_reg(). Arnd
