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[84.3.50.134]) by smtp.gmail.com with ESMTPSA id x2sm13624867wrn.81.2019.10.21.02.02.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Oct 2019 02:02:05 -0700 (PDT) Date: Mon, 21 Oct 2019 11:02:03 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: x86@kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com, torvalds@linux-foundation.org, tglx@linutronix.de, namit@vmware.com, hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com, jeyu@kernel.org Subject: Re: [PATCH v4 09/16] x86/alternative: Remove text_poke_loc::len Message-ID: <20191021090203.GA88859@gmail.com> References: <20191018073525.768931536@infradead.org> <20191018074634.457534206@infradead.org> <20191021085830.GA102207@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191021085830.GA102207@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Ingo Molnar wrote: > > * Peter Zijlstra wrote: > > > * Second step: update all but the first byte of the patched range. > > */ > > for (do_sync = 0, i = 0; i < nr_entries; i++) { > > - if (tp[i].len - sizeof(int3) > 0) { > > + int len = text_opcode_size(tp[i].opcode); > > + > > + if (len - sizeof(int3) > 0) { > > text_poke((char *)tp[i].addr + sizeof(int3), > > (const char *)tp[i].text + sizeof(int3), > > - tp[i].len - sizeof(int3)); > > + len - sizeof(int3)); > > do_sync++; > > } > > Readability side note: 'sizeof(int3)' is a really weird way to write '1' > and I had to double check it's not measuring the size of some larger > entity. > > I think it might make sense to just break out INT3_SIZE from > arch/x86/kernel/kprobes/opt.c into a header, rename it to INS_INT3_SIZE > and define it to 1, because the opt.c use is pretty obfuscated as well: > > #define INT3_SIZE sizeof(kprobe_opcode_t) > > Where kprobe_opcode_t is u8 on x86 (and won't ever be anything else). > > ? Oh, the latter is done in your patch #11 already. Nice! Thanks, Ingo