Re: [PATCH v38 18/24] x86/vdso: Add support for exception fixup in vDSO functions

[Borislav Petkov]

On Tue, Sep 15, 2020 at 02:28:36PM +0300, Jarkko Sakkinen wrote:
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> 
> The basic concept and implementation is very similar to the kernel's
> exception fixup mechanism.  The key differences are that the kernel
> handler is hardcoded and the fixup entry addresses are relative to
> the overall table as opposed to individual entries.

...

This gist of this commit message should be also in
Documentation/x86/sgx.rst

And I already said the same thing during v33 review:

"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..."

...

> 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 */
> +

Also from last time:

.git/rebase-apply/patch:122: new blank line at EOF.
+


-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette