From: Peter Zijlstra <peterz@infradead.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Juergen Gross <jgross@suse.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v4 2/5] x86/alternative: add indirect call patching
Date: Tue, 14 Nov 2023 13:50:28 +0100 [thread overview]
Message-ID: <20231114125028.GX3818@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20231114123737.GBZVNqEXKgt+6P1Wiv@fat_crate.local>
On Tue, Nov 14, 2023 at 01:37:37PM +0100, Borislav Petkov wrote:
> > +#ifdef CONFIG_X86_64
> > + /* ff 15 00 00 00 00 call *0x0(%rip) */
> > + target = *(void **)(instr + a->instrlen + *(s32 *)(instr + 2));
> > +#else
> > + /* ff 15 00 00 00 00 call *0x0 */
> > + target = *(void **)(*(s32 *)(instr + 2));
> > +#endif
> > + if (!target)
> > + target = bug;
> > +
> > + /* (BUG_func - .) + (target - BUG_func) := target - . */
> > + *(s32 *)(insn_buff + 1) += target - bug;
>
> If I squint hard enough, this looks like it is replacing one call with
> another. We have a C macro alternative_call() which does exactly that.
> Why can't you define an asm version ALTERNATIVE_CALL and use it
> instead of using adding a new flag? We have 16 possible ones in total.
This loads the function target from the pv_ops table. We can't otherwise
do this.
next prev parent reply other threads:[~2023-11-14 12:50 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-30 14:25 [PATCH v4 0/5] x86/paravirt: Get rid of paravirt patching Juergen Gross
2023-10-30 14:25 ` [PATCH v4 1/5] x86/paravirt: move some functions and defines to alternative Juergen Gross
2023-10-30 14:25 ` [PATCH v4 2/5] x86/alternative: add indirect call patching Juergen Gross
2023-11-14 12:37 ` Borislav Petkov
2023-11-14 12:50 ` Peter Zijlstra [this message]
2023-11-14 13:47 ` Borislav Petkov
2023-11-14 14:18 ` Peter Zijlstra
2023-11-14 14:27 ` Borislav Petkov
2023-11-14 14:35 ` Juergen Gross
2023-11-14 12:56 ` Juergen Gross
2023-11-14 15:06 ` Borislav Petkov
2023-11-14 16:16 ` Juergen Gross
2023-10-30 14:25 ` [PATCH v4 3/5] x86/paravirt: introduce ALT_NOT_XEN Juergen Gross
2023-11-14 15:09 ` Borislav Petkov
2023-11-14 16:17 ` Juergen Gross
2023-10-30 14:25 ` [PATCH v4 4/5] x86/paravirt: switch mixed paravirt/alternative calls to alternative_2 Juergen Gross
2023-11-21 18:45 ` Borislav Petkov
2023-11-29 10:08 ` Juergen Gross
2023-10-30 14:25 ` [PATCH v4 5/5] x86/paravirt: remove no longer needed paravirt patching code Juergen Gross
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