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Re: [PATCH] x86/asm: ELF metadata for simple cases
- To: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
- Date: Mon, 20 Feb 2023 11:51:01 +0000
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- Cc: Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
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- Thread-topic: [PATCH] x86/asm: ELF metadata for simple cases
> From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Sent: Monday, February 20, 2023 11:04 AM
> To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Jan Beulich
> <JBeulich@xxxxxxxx>; Roger Pau Monne <roger.pau@xxxxxxxxxx>; Wei Liu
> <wl@xxxxxxx>; Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>; Ross Lagerwall
> <ross.lagerwall@xxxxxxxxxx>
> Subject: [PATCH] x86/asm: ELF metadata for simple cases
>
> This is generally good practice, and necessary for livepatch binary diffing to
> work.
>
> With this, livepatching of the SVM entry path works. The only complication is
> with svm_stgi_label which is only used by oprofile to guestimate (not
> completely correctly) when an NMI hit guest context.
>
> Livepatching of VMX is still an open question, because the logic doesn't form
> anything remotely resembling functions. Both code fragments jump into each
> other so need to be updated in tandem. Also, both code fragment entries need
> trampolines in the case that patching actually occurs. For now, just treat it
> as a single function.
If it is treated as two functions and both functions are always included in
the live patch, would that work?
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Wei Liu <wl@xxxxxxx>
> CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> CC: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
> ---
> xen/arch/x86/clear_page.S | 3 +++
> xen/arch/x86/copy_page.S | 3 +++
> xen/arch/x86/hvm/svm/entry.S | 3 +++
> xen/arch/x86/hvm/vmx/entry.S | 3 +++
> 4 files changed, 12 insertions(+)
>
> diff --git a/xen/arch/x86/clear_page.S b/xen/arch/x86/clear_page.S
> index d9d524c79ecd..5b5622cc526f 100644
> --- a/xen/arch/x86/clear_page.S
> +++ b/xen/arch/x86/clear_page.S
> @@ -16,3 +16,6 @@ ENTRY(clear_page_sse2)
>
> sfence
> ret
> +
> + .type clear_page_sse2, @function
> + .size clear_page_sse2, . - clear_page_sse2
Would it be worth wrapping this pattern in a macro?
Ross
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