Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965106AbaGDNEz (ORCPT ); Fri, 4 Jul 2014 09:04:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33648 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932158AbaGDNEL (ORCPT ); Fri, 4 Jul 2014 09:04:11 -0400 From: Denys Vlasenko To: linux-kernel@vger.kernel.org Cc: Denys Vlasenko , Jim Keniston , Masami Hiramatsu , Srikar Dronamraju , Ingo Molnar , Oleg Nesterov Subject: [PATCH 2/3] uprobes: fix 1-byte opcode tables Date: Fri, 4 Jul 2014 15:03:45 +0200 Message-Id: <1404479026-9894-2-git-send-email-dvlasenk@redhat.com> In-Reply-To: <1404479026-9894-1-git-send-email-dvlasenk@redhat.com> References: <1404479026-9894-1-git-send-email-dvlasenk@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This change fixes 1-byte opcode tables so that only insns for which we have real reasons to disallow probing are marked with unset bits. To that end: Set bits for all prefix bytes. Their setting is ignored anyway - we check the bitmap against OPCODE1(insn), not against first byte. Keeping them set to 0 only confuses code reader with "why we don't support that opcode" question. Thus: enable bytes c4,c5 in 64-bit mode (VEX prefixes). Byte 62 (EVEX prefix) is not yet enabled since insn decoder does not support that yet. For 32-bit mode, enable probing of opcodes 63 (arpl) and d6 (salc). They don't require any special handling. For 64-bit mode, disable 9a and ea - these undefined opcodes were mistakenly left enabled. Signed-off-by: Denys Vlasenko CC: Jim Keniston CC: Masami Hiramatsu CC: Srikar Dronamraju CC: Ingo Molnar CC: Oleg Nesterov --- arch/x86/kernel/uprobes.c | 66 +++++++++++++---------------------------------- 1 file changed, 18 insertions(+), 48 deletions(-) diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index 9ba2fb2..40dfb4e 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -67,18 +67,6 @@ * to keep gcc from statically optimizing it out, as variable_test_bit makes * some versions of gcc to think only *(unsigned long*) is used. * - * Prefixes. Most marked as "bad", but it doesn't matter, since insn decoder - * won't report *prefixes* as OPCODE1(insn). - * 0f - 2-byte opcode prefix - * 26,2e,36,3e - es:/cs:/ss:/ds: - * 64 - fs: (marked as "good", why?) - * 65 - gs: (marked as "good", why?) - * 66 - operand-size prefix - * 67 - address-size prefix - * f0 - lock prefix - * f2 - repnz (marked as "good", why?) - * f3 - rep/repz (marked as "good", why?) - * * Opcodes we'll probably never support: * 6c-6f - ins,outs. SEGVs if used in userspace * e4-e7 - in,out imm. SEGVs if used in userspace @@ -105,31 +93,27 @@ * Not supported since kernel's handling of userspace single-stepping * (TF flag) is fragile. * cf - iret. Normally not used in userspace. Doesn't SEGV unless arguments are bad - * - * Opcodes which can be enabled right away: - * 63 - arpl. This insn has no unusual exceptions (it's basically an arith op). - * d6 - salc. Undocumented "sign-extend carry flag to AL" insn */ #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) static volatile u32 good_insns_32[256 / 32] = { /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ /* ---------------------------------------------- */ - W(0x00, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) | /* 00 */ + W(0x00, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* 00 */ W(0x10, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) , /* 10 */ - W(0x20, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1) | /* 20 */ - W(0x30, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1) , /* 30 */ + W(0x20, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 20 */ + W(0x30, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 30 */ W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */ W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */ - W(0x60, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */ + W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */ W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */ W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */ W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */ W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */ W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */ W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */ - W(0xd0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */ + W(0xd0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */ W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* e0 */ - W(0xf0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */ + W(0xf0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */ /* ---------------------------------------------- */ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ }; @@ -139,19 +123,6 @@ static volatile u32 good_insns_32[256 / 32] = { /* Good-instruction tables for 64-bit apps. * - * Prefixes. Most marked as "bad", but it doesn't matter, since insn decoder - * won't report *prefixes* as OPCODE1(insn). - * 0f - 2-byte opcode prefix - * 26,2e,36,3e - es:/cs:/ss:/ds: - * 40-4f - rex prefixes - * 64 - fs: (marked as "good", why?) - * 65 - gs: (marked as "good", why?) - * 66 - operand-size prefix - * 67 - address-size prefix - * f0 - lock prefix - * f2 - repnz (marked as "good", why?) - * f3 - rep/repz (marked as "good", why?) - * * Genuinely invalid opcodes: * 06,07 - formerly push/pop es * 0e - formerly push cs @@ -159,14 +130,13 @@ static volatile u32 good_insns_32[256 / 32] = { * 1e,1f - formerly push/pop ds * 27,2f,37,3f - formerly daa/das/aaa/aas * 60,61 - formerly pusha/popa - * 62 - formerly bound. EVEX prefix for AVX512 + * 62 - formerly bound. EVEX prefix for AVX512 (not yet supported) * 82 - formerly redundant encoding of Group1 - * 9a - formerly call seg:ofs (marked as "supported"???) - * c4,c5 - formerly les/lds. VEX prefixes for AVX + * 9a - formerly call seg:ofs * ce - formerly into * d4,d5 - formerly aam/aad * d6 - formerly undocumented salc - * ea - formerly jmp seg:ofs (marked as "supported"???) + * ea - formerly jmp seg:ofs * * Opcodes we'll probably never support: * 6c-6f - ins,outs. SEGVs if used in userspace @@ -190,22 +160,22 @@ static volatile u32 good_insns_32[256 / 32] = { static volatile u32 good_insns_64[256 / 32] = { /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ /* ---------------------------------------------- */ - W(0x00, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) | /* 00 */ + W(0x00, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1) | /* 00 */ W(0x10, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) , /* 10 */ - W(0x20, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) | /* 20 */ - W(0x30, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) , /* 30 */ - W(0x40, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 40 */ + W(0x20, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) | /* 20 */ + W(0x30, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) , /* 30 */ + W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */ W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */ - W(0x60, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */ + W(0x60, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */ W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */ W(0x80, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */ - W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */ + W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1) , /* 90 */ W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */ W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */ - W(0xc0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */ + W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */ W(0xd0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */ - W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* e0 */ - W(0xf0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */ + W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0) | /* e0 */ + W(0xf0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */ /* ---------------------------------------------- */ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ }; -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/