From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F675C47257 for ; Mon, 4 May 2020 05:42:46 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EF9FD20643 for ; Mon, 4 May 2020 05:42:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EF9FD20643 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=popple.id.au Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 49FsFb4zQXzDqb0 for ; Mon, 4 May 2020 15:42:43 +1000 (AEST) Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 49FsCm1FsszDqT2 for ; Mon, 4 May 2020 15:41:08 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=popple.id.au Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 49FsCk70PZz9sSc; Mon, 4 May 2020 15:41:06 +1000 (AEST) From: Alistair Popple To: Jordan Niethe Subject: Re: [PATCH v7 02/28] powerpc/xmon: Move breakpoint instructions to own array Date: Mon, 04 May 2020 15:41:03 +1000 Message-ID: <2060873.nxaIYQu1l1@townsend> In-Reply-To: <20200501034220.8982-3-jniethe5@gmail.com> References: <20200501034220.8982-1-jniethe5@gmail.com> <20200501034220.8982-3-jniethe5@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: npiggin@gmail.com, bala24@linux.ibm.com, naveen.n.rao@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, dja@axtens.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Friday, 1 May 2020 1:41:54 PM AEST Jordan Niethe wrote: > To execute an instruction out of line after a breakpoint, the NIP is set > to the address of struct bpt::instr. Here a copy of the instruction that > was replaced with a breakpoint is kept, along with a trap so normal flow > can be resumed after XOLing. The struct bpt's are located within the > data section. This is problematic as the data section may be marked as > no execute. > > Instead of each struct bpt holding the instructions to be XOL'd, make a > new array, bpt_table[], with enough space to hold instructions for the > number of supported breakpoints. A later patch will move this to the > text section. > Make struct bpt::instr a pointer to the instructions in bpt_table[] > associated with that breakpoint. This association is a simple mapping: > bpts[n] -> bpt_table[n * words per breakpoint]. Currently we only need > the copied instruction followed by a trap, so 2 words per breakpoint. > > Signed-off-by: Jordan Niethe > --- > v4: New to series > v5: - Do not use __section(), use a .space directive in .S file > - Simplify in_breakpoint_table() calculation > - Define BPT_SIZE > v6: - Seperate moving to text section > --- > arch/powerpc/xmon/xmon.c | 21 ++++++++++++--------- > 1 file changed, 12 insertions(+), 9 deletions(-) > > diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c > index f91ae2c9adbe..6ba7f66c1dd0 100644 > --- a/arch/powerpc/xmon/xmon.c > +++ b/arch/powerpc/xmon/xmon.c > @@ -98,7 +98,7 @@ static long *xmon_fault_jmp[NR_CPUS]; > /* Breakpoint stuff */ > struct bpt { > unsigned long address; > - unsigned int instr[2]; > + unsigned int *instr; > atomic_t ref_count; > int enabled; > unsigned long pad; > @@ -117,6 +117,10 @@ static unsigned bpinstr = 0x7fe00008; /* trap */ > > #define BP_NUM(bp) ((bp) - bpts + 1) > > +#define BPT_SIZE (sizeof(unsigned int) * 2) > +#define BPT_WORDS (BPT_SIZE / sizeof(unsigned int)) Minor nit-pick but IMHO this would be more logical if you defined BPT_WORDS first like so: #define BPT_WORDS (2) #define BPT_SIZE (sizeof(unsigned int) * BPT_WORDS) Otherwise this looks good and I think the offset calculations below are correct so: Reviewed-by: Alistair Popple > +static unsigned int bpt_table[NBPTS * BPT_WORDS]; > + > /* Prototypes */ > static int cmds(struct pt_regs *); > static int mread(unsigned long, void *, int); > @@ -854,15 +858,13 @@ static struct bpt *in_breakpoint_table(unsigned long > nip, unsigned long *offp) { > unsigned long off; > > - off = nip - (unsigned long) bpts; > - if (off >= sizeof(bpts)) > + off = nip - (unsigned long) bpt_table; > + if (off >= sizeof(bpt_table)) > return NULL; > - off %= sizeof(struct bpt); > - if (off != offsetof(struct bpt, instr[0]) > - && off != offsetof(struct bpt, instr[1])) > + *offp = off % BPT_SIZE; > + if (*offp != 0 && *offp != 4) > return NULL; > - *offp = off - offsetof(struct bpt, instr[0]); > - return (struct bpt *) (nip - off); > + return bpts + (off / BPT_SIZE); > } > > static struct bpt *new_breakpoint(unsigned long a) > @@ -877,7 +879,8 @@ static struct bpt *new_breakpoint(unsigned long a) > for (bp = bpts; bp < &bpts[NBPTS]; ++bp) { > if (!bp->enabled && atomic_read(&bp->ref_count) == 0) { > bp->address = a; > - patch_instruction(&bp->instr[1], bpinstr); > + bp->instr = bpt_table + ((bp - bpts) * BPT_WORDS); > + patch_instruction(bp->instr + 1, bpinstr); > return bp; > } > }