From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751742AbeAPOhh (ORCPT + 1 other); Tue, 16 Jan 2018 09:37:37 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:44699 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751306AbeAPOen (ORCPT ); Tue, 16 Jan 2018 09:34:43 -0500 Message-Id: <20180116143241.236771093@infradead.org> User-Agent: quilt/0.63-1 Date: Tue, 16 Jan 2018 15:28:31 +0100 From: Peter Zijlstra To: David Woodhouse , Josh Poimboeuf Cc: linux-kernel@vger.kernel.org, Dave Hansen , Ashok Raj , Thomas Gleixner , Tim Chen , Andy Lutomirski , Linus Torvalds , Greg KH , Andrea Arcangeli , Andi Kleen , Arjan Van De Ven , Dan Williams , Paolo Bonzini , Jun Nakajima , Asit Mallick , Peter Zijlstra , Borislav Petkov Subject: [PATCH v2 06/10] objtool: Implement jump_assert for _static_cpu_has() References: <20180116142825.376986833@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-objtool-static_cpu_has.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Unlike the jump_label bits, static_cpu_has is implemented with alternatives. We use the new type field to distinguish them from any other alternatives Like jump_labels, make static_cpu_has set static_jump_dest on the instructions after the static branch such that we can assert on it. Cc: Borislav Petkov Cc: Thomas Gleixner Cc: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) --- tools/objtool/check.c | 21 +++++++++++++++++++++ tools/objtool/special.c | 11 +++++++++++ tools/objtool/special.h | 1 + 3 files changed, 33 insertions(+) --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -636,6 +636,12 @@ static int handle_group_alt(struct objto fake_jump->ignore = true; if (!special_alt->new_len) { + /* + * The NOP case for _static_cpu_has() + */ + if (special_alt->static_feat) + fake_jump->jump_dest->static_jump_dest = true; + *new_insn = fake_jump; return 0; } @@ -664,6 +670,21 @@ static int handle_group_alt(struct objto insn->sec, insn->offset); return -1; } + + if (special_alt->static_feat) { + if (insn->type != INSN_JUMP_UNCONDITIONAL) { + WARN_FUNC("not an unconditional jump in _static_cpu_has()", + insn->sec, insn->offset); + } + if (insn->jump_dest == fake_jump) { + WARN_FUNC("jump inside alternative for _static_cpu_has()", + insn->sec, insn->offset); + } + /* + * The JMP+disp case for _static_cpu_has() + */ + insn->jump_dest->static_jump_dest = true; + } } if (!last_new_insn) { --- a/tools/objtool/special.c +++ b/tools/objtool/special.c @@ -40,6 +40,11 @@ #define ALT_FEATURE_OFFSET 8 #define ALT_ORIG_LEN_OFFSET 10 #define ALT_NEW_LEN_OFFSET 11 +#define ALT_PADDING_OFFSET 12 +#define ALT_TYPE_OFFSET 13 + +#define ALT_TYPE_DEFAULT 0 +#define ALT_TYPE_STATIC_CPU_HAS 1 #define X86_FEATURE_POPCNT (4*32+23) @@ -99,10 +104,13 @@ static int get_alt_entry(struct elf *elf if (entry->feature) { unsigned short feature; + unsigned char type; feature = *(unsigned short *)(sec->data->d_buf + offset + entry->feature); + type = *(unsigned char *)(sec->data->d_buf + offset + ALT_TYPE_OFFSET); + /* * It has been requested that we don't validate the !POPCNT * feature path which is a "very very small percentage of @@ -110,6 +118,9 @@ static int get_alt_entry(struct elf *elf */ if (feature == X86_FEATURE_POPCNT) alt->skip_orig = true; + + if (type == ALT_TYPE_STATIC_CPU_HAS) + alt->static_feat = true; } orig_rela = find_rela_by_dest(sec, offset + entry->orig); --- a/tools/objtool/special.h +++ b/tools/objtool/special.h @@ -27,6 +27,7 @@ struct special_alt { bool group; bool skip_orig; bool jump_or_nop; + bool static_feat; struct section *orig_sec; unsigned long orig_off;