Messages in this thread Patch in this message | | | Date | Mon, 29 Jun 2020 19:10:22 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v33 15/21] x86/vdso: Add support for exception fixup in vDSO functions |
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On Thu, Jun 18, 2020 at 01:08:37AM +0300, Jarkko Sakkinen wrote: ... > intended benefit of massaging GCC's inlining algorithm is unlikely to > realized in the vDSO any time soon, if ever.
That is a very good explanation and I would prefer if it would be in a sgx-specific README or so instead of it getting lost in git...
> +bool fixup_vdso_exception(struct pt_regs *regs, int trapnr, > + unsigned long error_code, unsigned long fault_addr) > +{ > + const struct vdso_image *image = current->mm->context.vdso_image; > + const struct vdso_exception_table_entry *extable; > + unsigned int nr_entries, i; > + unsigned long base; > + > + /* > + * Do not attempt to fixup #DB or #BP. It's impossible to identify > + * whether or not a #DB/#BP originated from within an SGX enclave and > + * SGX enclaves are currently the only use case for vDSO fixup. > + */
So this is all fine and dandy but nowhere do I see the code doing:
if (am_I_an_sgx_enclave(tsk)) fixup_vdso_exception()
because that vDSO exception fixup, albeit it looking kinda generic, is SGX-only for now. So it should be designed to run only for SGX enclaves for now.
Also, is there any particular reason for fixup_vdso_exception() to be in arch/x86/entry/vdso/extable.c instead of in arch/x86/mm/extable.c?
I mean, it gets called by traps.c so it looks like normal kernel code to me or am I missing some vdso magic?
And built only when CONFIG_INTEL_SGX is enabled.
And so on...
...
> diff --git a/arch/x86/entry/vdso/extable.h b/arch/x86/entry/vdso/extable.h > new file mode 100644 > index 000000000000..aafdac396948 > --- /dev/null > +++ b/arch/x86/entry/vdso/extable.h > @@ -0,0 +1,29 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __VDSO_EXTABLE_H > +#define __VDSO_EXTABLE_H > + > +/* > + * Inject exception fixup for vDSO code. Unlike normal exception fixup, > + * vDSO uses a dedicated handler the addresses are relative to the overall > + * exception table, not each individual entry. > + */ > +#ifdef __ASSEMBLY__ > +#define _ASM_VDSO_EXTABLE_HANDLE(from, to) \ > + ASM_VDSO_EXTABLE_HANDLE from to > + > +.macro ASM_VDSO_EXTABLE_HANDLE from:req to:req > + .pushsection __ex_table, "a" > + .long (\from) - __ex_table > + .long (\to) - __ex_table > + .popsection > +.endm > +#else > +#define _ASM_VDSO_EXTABLE_HANDLE(from, to) \ > + ".pushsection __ex_table, \"a\"\n" \ > + ".long (" #from ") - __ex_table\n" \ > + ".long (" #to ") - __ex_table\n" \ > + ".popsection\n" > +#endif > + > +#endif /* __VDSO_EXTABLE_H */ > + .git/rebase-apply/patch:122: new blank line at EOF. +
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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