On Fri, Mar 8, 2019 at 6:52 AM Tong Bo <bo.tong@xxxxxxxxx> wrote: > > Atom-based CPUs trigger stack fault when invoke 32-bit SYSENTER instruction > with invalid register values. So we also need SIGBUS handling in this case. > > Following is assembly when the fault exception happens. > > (gdb) disassemble $eip > Dump of assembler code for function __kernel_vsyscall: > 0xf7fd8fe0 <+0>: push %ecx > 0xf7fd8fe1 <+1>: push %edx > 0xf7fd8fe2 <+2>: push %ebp > 0xf7fd8fe3 <+3>: mov %esp,%ebp > 0xf7fd8fe5 <+5>: sysenter > 0xf7fd8fe7 <+7>: int $0x80 > => 0xf7fd8fe9 <+9>: pop %ebp > 0xf7fd8fea <+10>: pop %edx > 0xf7fd8feb <+11>: pop %ecx > 0xf7fd8fec <+12>: ret > End of assembler dump. > > According to Intel SDM, this could also be a Stack Segment Fault(#SS, 12), > except a normal Page Fault(#PF, 14). Especially, in section 6.9 of Vol.3A, > both stack and page faults are within the 10th(lowest priority) class, and > as it said, "exceptions within each class are implementation-dependent and > may vary from processor to processor". It's expected for processors like > Intel Atom to trigger stack fault(SIGBUS), while we get page fault(SIGSEGV) > from common Core processors. Acked-by: Andy Lutomirski <luto@xxxxxxxxxx> but: > - sethandler(SIGSEGV, sigsegv, SA_ONSTACK); > + sethandler(SIGSEGV, sigsegv_or_sigbus, SA_ONSTACK); > + /* The actual exception can vary. On Atom CPUs, we get #SS Can whoever commits this fix the comment formatting? That should be: /* * first line here --Andy
