From: Peter Zijlstra <peterz@infradead.org>
To: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org, jpoimboe@redhat.com, jgross@suse.com,
mbenes@suse.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 02/14] x86/alternatives: Optimize optimize_nops()
Date: Mon, 22 Mar 2021 09:17:57 +0100 [thread overview]
Message-ID: <YFhStWee0OrxBn5F@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210321120647.GB14446@zn.tnic>
On Sun, Mar 21, 2021 at 01:06:47PM +0100, Borislav Petkov wrote:
> I think I've made this simpler; pasting the whole function and not the
> diff because former is easier to read:
You've make it only replace a single stream of NOPs. Which is probably
fine, but... :-)
So mine, while a little more complicated, will replace any number of NOP
streams in any location. Saves having to worry about if we missed some
stupid corner case somewhere.
Anyway, I think I got it slightly wrong.. How's this one?
---
static void __init_or_module noinline optimize_nops(struct alt_instr *a, u8 *instr)
{
int nops = 0, i = 0;
bool done = false;
struct insn insn;
u8 *nop = NULL;
do {
if (insn_decode_kernel(&insn, &instr[i]))
return;
if (insn.length == 1 && insn.opcode.bytes[0] == 0x90)
nops++;
else if (nops)
nop = &instr[i - nops];
if (i + insn.length >= a->instrlen) {
nop = &instr[i - nops];
done = true;
}
if (nop) {
unsigned long flags;
local_irq_save(flags);
add_nops(nop, nops);
local_irq_restore(flags);
DUMP_BYTES(instr, a->instrlen, "%px: [%d:%d) optimized NOPs: ",
instr, (int)(unsigned long)(nop-instr), nops);
nops = 0;
nop = NULL;
}
i += insn.length;
} while (!done);
WARN_ON_ONCE(nop);
}
next prev parent reply other threads:[~2021-03-22 8:20 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-18 17:11 [PATCH v2 00/14] x86,objtool: Optimize !RETPOLINE Peter Zijlstra
2021-03-18 17:11 ` [PATCH v2 01/14] x86: Add insn_decode_kernel() Peter Zijlstra
2021-03-19 10:40 ` Borislav Petkov
2021-03-18 17:11 ` [PATCH v2 02/14] x86/alternatives: Optimize optimize_nops() Peter Zijlstra
2021-03-21 12:06 ` Borislav Petkov
2021-03-22 8:17 ` Peter Zijlstra [this message]
2021-03-22 11:07 ` Borislav Petkov
2021-03-18 17:11 ` [PATCH v2 03/14] x86/retpoline: Simplify retpolines Peter Zijlstra
2021-03-19 17:18 ` David Laight
2021-03-22 9:32 ` Peter Zijlstra
2021-03-22 15:41 ` David Laight
2021-03-18 17:11 ` [PATCH v2 04/14] objtool: Correctly handle retpoline thunk calls Peter Zijlstra
2021-03-18 17:11 ` [PATCH v2 05/14] objtool: Per arch retpoline naming Peter Zijlstra
2021-03-19 2:38 ` Josh Poimboeuf
2021-03-19 9:07 ` Peter Zijlstra
2021-03-18 17:11 ` [PATCH v2 06/14] objtool: Fix static_call list generation Peter Zijlstra
2021-03-22 12:44 ` Miroslav Benes
2021-03-18 17:11 ` [PATCH v2 07/14] objtool: Rework rebuild_reloc logic Peter Zijlstra
2021-03-18 17:11 ` [PATCH v2 08/14] objtool: Add elf_create_reloc() helper Peter Zijlstra
2021-03-19 1:42 ` Josh Poimboeuf
2021-03-19 9:47 ` Peter Zijlstra
2021-03-19 15:12 ` Josh Poimboeuf
2021-03-19 15:24 ` Peter Zijlstra
2021-03-19 15:37 ` Josh Poimboeuf
2021-03-18 17:11 ` [PATCH v2 09/14] objtool: Extract elf_strtab_concat() Peter Zijlstra
2021-03-19 2:10 ` Josh Poimboeuf
2021-03-19 9:52 ` Peter Zijlstra
2021-03-18 17:11 ` [PATCH v2 10/14] objtool: Extract elf_symbol_add() Peter Zijlstra
2021-03-19 2:14 ` Josh Poimboeuf
2021-03-19 9:54 ` Peter Zijlstra
2021-03-19 15:04 ` Josh Poimboeuf
2021-03-18 17:11 ` [PATCH v2 11/14] objtool: Add elf_create_undef_symbol() Peter Zijlstra
2021-03-19 2:29 ` Josh Poimboeuf
2021-03-19 7:56 ` Peter Zijlstra
2021-03-18 17:11 ` [PATCH v2 12/14] objtool: Allow archs to rewrite retpolines Peter Zijlstra
2021-03-19 2:54 ` Josh Poimboeuf
2021-03-19 11:21 ` Peter Zijlstra
2021-03-19 13:28 ` Peter Zijlstra
2021-03-18 17:11 ` [PATCH v2 13/14] objtool: Skip magical retpoline .altinstr_replacement Peter Zijlstra
2021-03-18 17:11 ` [PATCH v2 14/14] objtool,x86: Rewrite retpoline thunk calls Peter Zijlstra
2021-03-19 3:29 ` Josh Poimboeuf
2021-03-19 8:06 ` Peter Zijlstra
2021-03-19 15:30 ` Josh Poimboeuf
2021-03-19 15:56 ` Peter Zijlstra
2021-03-19 22:52 ` Josh Poimboeuf
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