From patchwork Tue Mar 13 20:59:39 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Garnier X-Patchwork-Id: 10280801 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 5EFBF6038F for ; Tue, 13 Mar 2018 21:06:06 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4CB83284BD for ; Tue, 13 Mar 2018 21:06:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3BBF0284CE; Tue, 13 Mar 2018 21:06:06 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.3 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 14C2A284BD for ; Tue, 13 Mar 2018 21:06:04 +0000 (UTC) Received: (qmail 22182 invoked by uid 550); 13 Mar 2018 21:01:29 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 21880 invoked from network); 13 Mar 2018 21:01:16 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=vO/yjXq+42QmCGcXYXbNUwLftfo2inVaVcUUtnJzwug=; b=iEvcJA4ymFiim6ZKRA771n8MSyUSiMAl+XCYOtTjXw68Ry2DrPsvbKcFFnZ2uhAziY BnlQ/bniY5jtj2wtZDOSu73hiFDXuv7zrAtDU1wUAtN83WS5UTN3zOmggQRaansav9a9 m0vu8tLMWlolYTeLuqCUThf/yboD1VAJ93h0AJFJsSLE0FZ08fl7g0iTTb7Hg9XCAABC y49jhfyVHfNj7Ir6xeqmV3ZLtTiMaGEhpRomLEmGWyk5qVZSZUnrKhL8HHJSA4IqNGvn fZzij/XWEgnqJPJfB+oEN/dyCh4up6HDzu3eVMZtPLTkqXLPj3KyEurXIntKBUiDcu5a KDIA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=vO/yjXq+42QmCGcXYXbNUwLftfo2inVaVcUUtnJzwug=; b=fRdw+3O30QsnGC1MRlt/NY3x8wlRjZl5ef7yReTbN1wsRmdL/ssf+/glcRcFj7xADb 6x5XpJIULx8OaeJ7JEhYpu84a+IwuTn80EbC07Y7C1km6aORMziNmjS/IzaIooRkPbX5 OK2UAkOWkPe1K98+xvLaEY9EQ82qS4ubKqen3TQpgTBD/44lobWj4Lm80rvI3sXvJRN/ BJB5gR0D79FVy0+iLDGJBaQSVxk84n00IPQQaXdDb7VCdK3ATJuhxviTt3H0wJop6qRI +Hb5ua3BaO1l9AVC3U/bkssbimxV1rW4Mv0NyEH5OvJkjQ+mFsUt84b2W/1XaCcxzK1q svSQ== X-Gm-Message-State: AElRT7GlW57WYdJBLG0jBoOzFyonKO3GDWS8tb2205Bi8SNBKovadeTq +7YnbiqIvRlPQxTD8NLaUEVtBQ== X-Google-Smtp-Source: AG47ELt5ip2t4ItKin8qQo784oQyT8OQsG46mYSVgMDHA78mI7Lz2HCXakO3ahkYtgl3UnK6mMhJRg== X-Received: by 10.99.110.137 with SMTP id j131mr1587537pgc.85.1520974863442; Tue, 13 Mar 2018 14:01:03 -0700 (PDT) From: Thomas Garnier To: Herbert Xu , "David S . Miller" , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Peter Zijlstra , Josh Poimboeuf , Greg Kroah-Hartman , Kate Stewart , Thomas Garnier , Arnd Bergmann , Philippe Ombredanne , Arnaldo Carvalho de Melo , Andrey Ryabinin , Matthias Kaehlcke , Kees Cook , Tom Lendacky , "Kirill A . Shutemov" , Andy Lutomirski , Dominik Brodowski , Borislav Petkov , Borislav Petkov , "Rafael J . Wysocki" , Len Brown , Pavel Machek , Juergen Gross , Alok Kataria , Steven Rostedt , Tejun Heo , Christoph Lameter , Dennis Zhou , Boris Ostrovsky , David Woodhouse , Alexey Dobriyan , "Paul E . McKenney" , Andrew Morton , Nicolas Pitre , Randy Dunlap , "Luis R . Rodriguez" , Christopher Li , Jason Baron , Ashish Kalra , Kyle McMartin , Dou Liyang , Lukas Wunner , Petr Mladek , Sergey Senozhatsky , Masahiro Yamada , Ingo Molnar , Nicholas Piggin , Cao jin , "H . J . Lu" , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Joerg Roedel , Dave Hansen , Rik van Riel , Jia Zhang , Jiri Slaby , Kyle Huey , Jonathan Corbet , Matthew Wilcox , Michal Hocko , Rob Landley , Baoquan He , Daniel Micay , =?UTF-8?q?Jan=20H=20=2E=20Sch=C3=B6nherr?= Cc: x86@kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v2 21/27] x86/ftrace: Adapt function tracing for PIE support Date: Tue, 13 Mar 2018 13:59:39 -0700 Message-Id: <20180313205945.245105-22-thgarnie@google.com> X-Mailer: git-send-email 2.16.2.660.g709887971b-goog In-Reply-To: <20180313205945.245105-1-thgarnie@google.com> References: <20180313205945.245105-1-thgarnie@google.com> X-Virus-Scanned: ClamAV using ClamSMTP When using -fPIE/PIC with function tracing, the compiler generates a call through the GOT (call *__fentry__@GOTPCREL). This instruction takes 6 bytes instead of 5 on the usual relative call. If PIE is enabled, replace the 6th byte of the GOT call by a 1-byte nop so ftrace can handle the previous 5-bytes as before. Position Independent Executable (PIE) support will allow to extended the KASLR randomization range below the -2G memory limit. Signed-off-by: Thomas Garnier --- arch/x86/include/asm/ftrace.h | 6 +++-- arch/x86/include/asm/sections.h | 4 ++++ arch/x86/kernel/ftrace.c | 42 +++++++++++++++++++++++++++++++-- 3 files changed, 48 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h index 09ad88572746..61fa02d81b95 100644 --- a/arch/x86/include/asm/ftrace.h +++ b/arch/x86/include/asm/ftrace.h @@ -25,9 +25,11 @@ extern void __fentry__(void); static inline unsigned long ftrace_call_adjust(unsigned long addr) { /* - * addr is the address of the mcount call instruction. - * recordmcount does the necessary offset calculation. + * addr is the address of the mcount call instruction. PIE has always a + * byte added to the start of the function. */ + if (IS_ENABLED(CONFIG_X86_PIE)) + addr -= 1; return addr; } diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h index d6baf23782bc..cad292f62eed 100644 --- a/arch/x86/include/asm/sections.h +++ b/arch/x86/include/asm/sections.h @@ -12,4 +12,8 @@ extern struct exception_table_entry __stop___ex_table[]; extern char __end_rodata_hpage_align[]; #endif +#if defined(CONFIG_X86_PIE) +extern char __start_got[], __end_got[]; +#endif + #endif /* _ASM_X86_SECTIONS_H */ diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 01ebcb6f263e..21bde498f1a9 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -102,7 +102,7 @@ static const unsigned char *ftrace_nop_replace(void) static int ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code, - unsigned const char *new_code) + unsigned const char *new_code) { unsigned char replaced[MCOUNT_INSN_SIZE]; @@ -135,6 +135,44 @@ ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code, return 0; } +/* Bytes before call GOT offset */ +const unsigned char got_call_preinsn[] = { 0xff, 0x15 }; + +static int +ftrace_modify_initial_code(unsigned long ip, unsigned const char *old_code, + unsigned const char *new_code) +{ + unsigned char replaced[MCOUNT_INSN_SIZE + 1]; + + ftrace_expected = old_code; + + /* + * If PIE is not enabled or no GOT call was found, default to the + * original approach to code modification. + */ + if (!IS_ENABLED(CONFIG_X86_PIE) + || probe_kernel_read(replaced, (void *)ip, sizeof(replaced)) + || memcmp(replaced, got_call_preinsn, sizeof(got_call_preinsn))) + return ftrace_modify_code_direct(ip, old_code, new_code); + + /* + * Build a nop slide with a 5-byte nop and 1-byte nop to keep the ftrace + * hooking algorithm working with the expected 5 bytes instruction. + */ + memcpy(replaced, new_code, MCOUNT_INSN_SIZE); + replaced[MCOUNT_INSN_SIZE] = ideal_nops[1][0]; + + ip = text_ip_addr(ip); + + if (probe_kernel_write((void *)ip, replaced, sizeof(replaced))) + return -EPERM; + + sync_core(); + + return 0; + +} + int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { @@ -153,7 +191,7 @@ int ftrace_make_nop(struct module *mod, * just modify the code directly. */ if (addr == MCOUNT_ADDR) - return ftrace_modify_code_direct(rec->ip, old, new); + return ftrace_modify_initial_code(rec->ip, old, new); ftrace_expected = NULL;