From patchwork Fri May 22 13:33:18 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Ellerman X-Patchwork-Id: 1296264 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 ozlabs.org (Postfix) with ESMTPS id 49T6tG4fwbz9sRW for ; Fri, 22 May 2020 23:35:02 +1000 (AEST) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=gaKht3gO; dkim-atps=neutral Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 49T6tF74NxzDqw1 for ; Fri, 22 May 2020 23:35:01 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Received: from ozlabs.org (bilbo.ozlabs.org [203.11.71.1]) (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 49T6qv4zpZzDqcc for ; Fri, 22 May 2020 23:32:59 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=gaKht3gO; dkim-atps=neutral Received: by ozlabs.org (Postfix) id 49T6qt5vjSz9sSw; Fri, 22 May 2020 23:32:58 +1000 (AEST) Delivered-To: linuxppc-dev@ozlabs.org Received: by ozlabs.org (Postfix, from userid 1034) id 49T6qt4zhqz9sSx; Fri, 22 May 2020 23:32:58 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ellerman.id.au; s=201909; t=1590154378; bh=+Y7LrcYTXNS3+DQ4I2THCQh3unpkCQN3QSE9DqukxHc=; h=From:To:Cc:Subject:Date:From; b=gaKht3gOrkW4pcN9euIdzG0Ira4LBFtTjI4MWXVgYgborENwnOBVyQrL9g5H9Vt3g ixDqKkyjsUODSKJ22spMgCKqtYPRKy+GZ8cTE+xb2n/ZRwSrE1VI9kvFEH+5ehxfPt YMh1JwFxXJ/o6XKvAbQTnIWI7uzg1i6tE0maIFcN8/BWmAS11q0bYy7RcbLWJ4+t7y AQkN3csCL26hAhyXJMPiFRShEZYA236T7w5hp4YTkrtFpJ47xVtohWdLgqu4yvn8XN CwHDC4F81v+hShYYwYVpxSjKlyVxwyrQK27xW3gw/oxiPMdfVpAfUB9jTTC6S+ZLet lVSK/6L3v300Q== From: Michael Ellerman To: linuxppc-dev@ozlabs.org Subject: [PATCH v2] powerpc: Add ppc_inst_next() Date: Fri, 22 May 2020 23:33:18 +1000 Message-Id: <20200522133318.1681406-1-mpe@ellerman.id.au> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 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: christophe.leroy@c-s.fr, jniethe5@gmail.com Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" In a few places we want to calculate the address of the next instruction. Previously that was simple, we just added 4 bytes, or if using a u32 * we incremented that pointer by 1. But prefixed instructions make it more complicated, we need to advance by either 4 or 8 bytes depending on the actual instruction. We also can't do pointer arithmetic using struct ppc_inst, because it is always 8 bytes in size on 64-bit, even though we might only need to advance by 4 bytes. So add a ppc_inst_next() helper which calculates the location of the next instruction, if the given instruction was located at the given address. Note the instruction doesn't need to actually be at the address in memory. Although it would seem natural for the value to be passed by value, that makes it too easy to write a loop that will read off the end of a page, eg: for (; src < end; src = ppc_inst_next(src, *src), dest = ppc_inst_next(dest, *dest)) As noticed by Christophe and Jordan, if end is the exact end of a page, and the next page is not mapped, this will fault, because *dest will read 8 bytes, 4 bytes into the next page. So value is passed by reference, so the helper can be careful to use ppc_inst_read() on it. Signed-off-by: Michael Ellerman Reviewed-by: Jordan Niethe --- arch/powerpc/include/asm/inst.h | 13 +++++++++++++ arch/powerpc/kernel/uprobes.c | 2 +- arch/powerpc/lib/feature-fixups.c | 15 ++++++++------- arch/powerpc/xmon/xmon.c | 2 +- 4 files changed, 23 insertions(+), 9 deletions(-) v2: Pass the value as a pointer and use ppc_inst_read() on it. diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h index d82e0c99cfa1..5b756ba77ed2 100644 --- a/arch/powerpc/include/asm/inst.h +++ b/arch/powerpc/include/asm/inst.h @@ -100,6 +100,19 @@ static inline int ppc_inst_len(struct ppc_inst x) return ppc_inst_prefixed(x) ? 8 : 4; } +/* + * Return the address of the next instruction, if the instruction @value was + * located at @location. + */ +static inline struct ppc_inst *ppc_inst_next(void *location, struct ppc_inst *value) +{ + struct ppc_inst tmp; + + tmp = ppc_inst_read(value); + + return location + ppc_inst_len(tmp); +} + int probe_user_read_inst(struct ppc_inst *inst, struct ppc_inst __user *nip); diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c index 83e883e1a42d..d200e7df7167 100644 --- a/arch/powerpc/kernel/uprobes.c +++ b/arch/powerpc/kernel/uprobes.c @@ -112,7 +112,7 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) * support doesn't exist and have to fix-up the next instruction * to be executed. */ - regs->nip = utask->vaddr + ppc_inst_len(ppc_inst_read(&auprobe->insn)); + regs->nip = (unsigned long)ppc_inst_next((void *)utask->vaddr, &auprobe->insn); user_disable_single_step(current); return 0; diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c index 80f320c2e189..4c0a7ee9fa00 100644 --- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c @@ -68,7 +68,7 @@ static int patch_alt_instruction(struct ppc_inst *src, struct ppc_inst *dest, static int patch_feature_section(unsigned long value, struct fixup_entry *fcur) { - struct ppc_inst *start, *end, *alt_start, *alt_end, *src, *dest; + struct ppc_inst *start, *end, *alt_start, *alt_end, *src, *dest, nop; start = calc_addr(fcur, fcur->start_off); end = calc_addr(fcur, fcur->end_off); @@ -84,14 +84,15 @@ static int patch_feature_section(unsigned long value, struct fixup_entry *fcur) src = alt_start; dest = start; - for (; src < alt_end; src = (void *)src + ppc_inst_len(ppc_inst_read(src)), - (dest = (void *)dest + ppc_inst_len(ppc_inst_read(dest)))) { + for (; src < alt_end; src = ppc_inst_next(src, src), + dest = ppc_inst_next(dest, dest)) { if (patch_alt_instruction(src, dest, alt_start, alt_end)) return 1; } - for (; dest < end; dest = (void *)dest + ppc_inst_len(ppc_inst(PPC_INST_NOP))) - raw_patch_instruction(dest, ppc_inst(PPC_INST_NOP)); + nop = ppc_inst(PPC_INST_NOP); + for (; dest < end; dest = ppc_inst_next(dest, &nop)) + raw_patch_instruction(dest, nop); return 0; } @@ -405,8 +406,8 @@ static void do_final_fixups(void) while (src < end) { inst = ppc_inst_read(src); raw_patch_instruction(dest, inst); - src = (void *)src + ppc_inst_len(inst); - dest = (void *)dest + ppc_inst_len(inst); + src = ppc_inst_next(src, src); + dest = ppc_inst_next(dest, dest); } #endif } diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index fb135f2cd6b0..65cf853a4d26 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -939,7 +939,7 @@ static void insert_bpts(void) } patch_instruction(bp->instr, instr); - patch_instruction((void *)bp->instr + ppc_inst_len(instr), + patch_instruction(ppc_inst_next(bp->instr, &instr), ppc_inst(bpinstr)); if (bp->enabled & BP_CIABR) continue;