Hi Bo,
On 5/17/19 1:02 AM, Tong, Bo wrote:
Is this patch going to be merged? Or still any blocking issue there?
Thanks, Bo
-----Original Message----- From: shuah [mailto:shuah@kernel.org] Sent: Friday, April 19, 2019 10:05 PM To: Tong, Bo bo.tong@intel.com; luto@kernel.org; x86@kernel.org Cc: linux-kselftest@vger.kernel.org; linux-kernel@vger.kernel.org; skhan@linuxfoundation.org; shuah@kernel.org Subject: Re: [PATCH v3] selftests/x86: Support Atom for syscall_arg_fault test
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
Looks like it got left behind in the confusion of which tree.
I will apply this to my tree.
thanks, -- Shuah