On Wed, Aug 28, 2019 at 05:13:59PM +0200, Arnd Bergmann wrote: > On Wed, Aug 28, 2019 at 11:00 AM Arnd Bergmann <[email protected]> wrote: > > On Tue, Aug 27, 2019 at 11:22 PM 'Nick Desaulniers' via Clang Built Linux > > <[email protected]> wrote: > I figured this one out as well: > > > http://paste.ubuntu.com/p/XjdDsypRxX/ > > 0x5BA1B7A1:arch/x86/ia32/ia32_signal.o: warning: objtool: > > ia32_setup_rt_frame()+0x238: call to memset() with UACCESS enabled > > 0x5BA1B7A1:arch/x86/kernel/signal.o: warning: objtool: > > __setup_rt_frame()+0x5b8: call to memset() with UACCESS enabled > > When CONFIG_KASAN is set, clang decides to use memset() to set > the first two struct members in this function: > > static inline void sas_ss_reset(struct task_struct *p) > { > p->sas_ss_sp = 0; > p->sas_ss_size = 0; > p->sas_ss_flags = SS_DISABLE; > } > > and that is called from save_altstack_ex(). Adding a barrier() after > the sas_ss_sp() works around the issue, but is certainly not the > best solution. Any other ideas?
Wow, is the compiler allowed to insert memset calls like that? Seems a bit overbearing, at least in a kernel context. I don't recall GCC ever doing it. -- Josh
