On Mon, Sep 28, 2020 at 08:54:01AM -0700, H.J. Lu wrote: > On Mon, Sep 28, 2020 at 8:43 AM Yu, Yu-cheng <yu-cheng.yu@xxxxxxxxx> wrote: > > > > On 9/25/2020 11:23 AM, Andrew Cooper wrote: > > > On 15/09/2020 12:28, Jarkko Sakkinen wrote: > > >> diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S > > >> new file mode 100644 > > >> index 000000000000..adbd59d41517 > > >> --- /dev/null > > >> +++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S > > >> @@ -0,0 +1,157 @@ > > >> +SYM_FUNC_START(__vdso_sgx_enter_enclave) > > >> <snip> > > >> +.Lretpoline: > > >> + call 2f > > >> +1: pause > > >> + lfence > > >> + jmp 1b > > >> +2: mov %rax, (%rsp) > > >> + ret > > > > > > I hate to throw further spanners in the work, but this is not compatible > > > with CET, and the user shadow stack work in progress. > > > > Hi Jarkko, > > > > These 1: and 2: targets are reached only from these few lines? If they > > are direct call/jmp targets, I think it is OK in terms of CET. If they > > are reached from an instruction like "jmp *%rax", then we need to put in > > an "endbr64". > > > > This also isn't compatible with shadow stack. > > -- > H.J. I have the now full picture of the problem thanks to Andrew's response [1]. And Dave Hansen just explained me in detail the context and background with [2]. So I'd guess this will get sorted out soon. If you don't mind I'll CC you to this commit when I send the next version? [1] https://lkml.org/lkml/2020/9/28/1153 [2] https://lkml.org/lkml/2020/9/25/1122 /Jarkko
