From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELtGGoz4VL261zIs8wupS1xU+y7PLZa6UbQ+HLFSzmcPUtDd/1OEBhUOEjAJwG8w6ACAKb7u ARC-Seal: i=1; a=rsa-sha256; t=1520975172; cv=none; d=google.com; s=arc-20160816; b=NaWghWjfgMf+aX2whXloFWkBFmGcIwf9BKcqxLdgylhIiQwCOSTwtJ/XiYCCRi+g3S AIxIJxidXqUzjsbKl4o2A6q+B0kV2RigWwqvKnIi1Z3qYJr5W8UMYrWO/ywvHe5iLTOd B3dnflI00GqR2iR6nsBNni3puBtff37TSXOrMjjzpjlck+I/GKgkZ3bG+BfOBCv7ztwE 0hDU0IGjwDyklvPSAiJ4oNuAKeeNDZLoauWYDI/WVOPF1mQrcNBZquHifVmHWtGnZWHh sTHh2tth95wZLw96tvH70Wpw5Tof/+gOSIu2C5q+KjGLfmUcGe1g2+F+1MiQ5KT7sRpO qjHg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature:delivered-to:list-id:list-subscribe:list-unsubscribe :list-help:list-post:precedence:mailing-list :arc-authentication-results; bh=vO/yjXq+42QmCGcXYXbNUwLftfo2inVaVcUUtnJzwug=; b=d19KC1osB+IiZm+DDcv7rEh12o95EKV0B4hcke7zoFhOcgHSrxZFSN4fLW7s1D1xDV LJ7loqpb8GVf6QTesRnQaRn2fcqwaSa3ZZwqa1GLN2iL/HDI6nqY9qalDL79USTw2oXn zsXmeqCvEnnVu5ZVET09pn4pramNY0EqD8AZsXhIKj+pxhFJQvrgv2jSI6zMCcUvE/Yk mwDwu8HZ/8Ym1YuTy5jtWNaVx50SbA98eLJsRXajxIFLBcIsqMOHQlrbd5liJnNwK0v2 n0aLKxEXK83ls0KeIxw+W5mLy4pOll1PkvMbaKETnR9vW99++0HlkiknyvN+rg95Dzor P0pw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=iEvcJA4y; spf=pass (google.com: domain of kernel-hardening-return-12544-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-12544-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=iEvcJA4y; spf=pass (google.com: domain of kernel-hardening-return-12544-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-12544-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm List-Post: List-Help: List-Unsubscribe: List-Subscribe: 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-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594858062425792867?= X-GMAIL-MSGID: =?utf-8?q?1594858062425792867?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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; -- 2.16.2.660.g709887971b-goog