On Fri, Mar 8, 2019 at 6:52 AM Tong Bo bo.tong@intel.com 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@kernel.org
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