Messages in this thread | | | Subject | Re: [PATCH v3] selftests/x86: Support Atom for syscall_arg_fault test | From | shuah <> | Date | Fri, 19 Apr 2019 08:04:35 -0600 |
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On 4/19/19 1:10 AM, Tong Bo 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. > > Signed-off-by: Tong Bo <bo.tong@intel.com> > Acked-by: Andy Lutomirski <luto@kernel.org> > --- > tools/testing/selftests/x86/syscall_arg_fault.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/x86/syscall_arg_fault.c b/tools/testing/selftests/x86/syscall_arg_fault.c > index 7db4fc9..d2548401 100644 > --- a/tools/testing/selftests/x86/syscall_arg_fault.c > +++ b/tools/testing/selftests/x86/syscall_arg_fault.c > @@ -43,7 +43,7 @@ static sigjmp_buf jmpbuf; > > static volatile sig_atomic_t n_errs; > > -static void sigsegv(int sig, siginfo_t *info, void *ctx_void) > +static void sigsegv_or_sigbus(int sig, siginfo_t *info, void *ctx_void) > { > ucontext_t *ctx = (ucontext_t*)ctx_void; > > @@ -73,7 +73,13 @@ int main() > if (sigaltstack(&stack, NULL) != 0) > err(1, "sigaltstack"); > > - sethandler(SIGSEGV, sigsegv, SA_ONSTACK); > + sethandler(SIGSEGV, sigsegv_or_sigbus, SA_ONSTACK); > + /* > + * The actual exception can vary. On Atom CPUs, we get #SS > + * instead of #PF when the vDSO fails to access the stack when > + * ESP is too close to 2^32, and #SS causes SIGBUS. > + */ > + sethandler(SIGBUS, sigsegv_or_sigbus, SA_ONSTACK); > sethandler(SIGILL, sigill, SA_ONSTACK); > > /* >
In case there is a dependency on x86 tree, here is my Ack
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
thanks, -- Shuah
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