Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755528Ab1BORF1 (ORCPT ); Tue, 15 Feb 2011 12:05:27 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60066 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752579Ab1BORFY (ORCPT ); Tue, 15 Feb 2011 12:05:24 -0500 Date: Tue, 15 Feb 2011 18:05:07 +0100 From: Jiri Olsa To: Masami Hiramatsu , mingo@elte.hu, ananth@in.ibm.com, davem@davemloft.net Cc: linux-kernel@vger.kernel.org Subject: [PATCH] kprobes - do not allow optimized kprobes in entry code Message-ID: <20110215170507.GD3135@jolsa.brq.redhat.com> References: <1297696354-6990-1-git-send-email-jolsa@redhat.com> <4D5A4A66.4010503@hitachi.com> <20110215123058.GB3135@jolsa.brq.redhat.com> <4D5AA209.7070309@hitachi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4D5AA209.7070309@hitachi.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5247 Lines: 173 You can crash the kernel using kprobe tracer by running: echo "p system_call_after_swapgs" > ./kprobe_events echo 1 > ./events/kprobes/enable The reason is that at the system_call_after_swapgs label, the kernel stack is not set up. If optimized kprobes are enabled, the user space stack is being used in this case (see optimized kprobe template) and this might result in a crash. There are several places like this over the entry code (entry_$BIT). As it seems there's no any reasonable/maintainable way to disable only those places where the stack is not ready, I switched off the whole entry code from kprobe optimizing. wbr, jirka Signed-off-by: Jiri Olsa --- arch/x86/ia32/ia32entry.S | 2 ++ arch/x86/kernel/entry_32.S | 6 ++++-- arch/x86/kernel/entry_64.S | 6 ++++-- arch/x86/kernel/kprobes.c | 8 ++++++++ arch/x86/kernel/vmlinux.lds.S | 1 + include/asm-generic/sections.h | 1 + include/asm-generic/vmlinux.lds.h | 6 ++++++ 7 files changed, 26 insertions(+), 4 deletions(-) diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index 0ed7896..50f1630 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -25,6 +25,8 @@ #define sysretl_audit ia32_ret_from_sys_call #endif + .section .entry.text, "ax" + #define IA32_NR_syscalls ((ia32_syscall_end - ia32_sys_call_table)/8) .macro IA32_ARG_FIXUP noebp=0 diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index c8b4efa..f5accf8 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -65,6 +65,8 @@ #define sysexit_audit syscall_exit_work #endif + .section .entry.text, "ax" + /* * We use macros for low-level operations which need to be overridden * for paravirtualization. The following will never clobber any registers: @@ -788,7 +790,7 @@ ENDPROC(ptregs_clone) */ .section .init.rodata,"a" ENTRY(interrupt) -.text +.section .entry.text, "ax" .p2align 5 .p2align CONFIG_X86_L1_CACHE_SHIFT ENTRY(irq_entries_start) @@ -807,7 +809,7 @@ vector=FIRST_EXTERNAL_VECTOR .endif .previous .long 1b - .text + .section .entry.text, "ax" vector=vector+1 .endif .endr diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 891268c..39f8d21 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -61,6 +61,8 @@ #define __AUDIT_ARCH_LE 0x40000000 .code64 + .section .entry.text, "ax" + #ifdef CONFIG_FUNCTION_TRACER #ifdef CONFIG_DYNAMIC_FTRACE ENTRY(mcount) @@ -744,7 +746,7 @@ END(stub_rt_sigreturn) */ .section .init.rodata,"a" ENTRY(interrupt) - .text + .section .entry.text .p2align 5 .p2align CONFIG_X86_L1_CACHE_SHIFT ENTRY(irq_entries_start) @@ -763,7 +765,7 @@ vector=FIRST_EXTERNAL_VECTOR .endif .previous .quad 1b - .text + .section .entry.text vector=vector+1 .endif .endr diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c index d91c477..d03bc1e 100644 --- a/arch/x86/kernel/kprobes.c +++ b/arch/x86/kernel/kprobes.c @@ -1276,6 +1276,14 @@ static int __kprobes can_optimize(unsigned long paddr) if (!kallsyms_lookup_size_offset(paddr, &size, &offset)) return 0; + /* + * Do not optimize in the entry code due to the unstable + * stack handling. + */ + if ((paddr >= (unsigned long ) __entry_text_start) && + (paddr < (unsigned long ) __entry_text_end)) + return 0; + /* Check there is enough space for a relative jump. */ if (size - offset < RELATIVEJUMP_SIZE) return 0; diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index e9f7a3c..0381e1f 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -105,6 +105,7 @@ SECTIONS SCHED_TEXT LOCK_TEXT KPROBES_TEXT + ENTRY_TEXT IRQENTRY_TEXT *(.fixup) *(.gnu.warning) diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index b3bfabc..c1a1216 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -11,6 +11,7 @@ extern char _sinittext[], _einittext[]; extern char _end[]; extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[]; extern char __kprobes_text_start[], __kprobes_text_end[]; +extern char __entry_text_start[], __entry_text_end[]; extern char __initdata_begin[], __initdata_end[]; extern char __start_rodata[], __end_rodata[]; diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index fe77e33..906c3ce 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -424,6 +424,12 @@ *(.kprobes.text) \ VMLINUX_SYMBOL(__kprobes_text_end) = .; +#define ENTRY_TEXT \ + ALIGN_FUNCTION(); \ + VMLINUX_SYMBOL(__entry_text_start) = .; \ + *(.entry.text) \ + VMLINUX_SYMBOL(__entry_text_end) = .; + #ifdef CONFIG_FUNCTION_GRAPH_TRACER #define IRQENTRY_TEXT \ ALIGN_FUNCTION(); \ -- 1.7.1 -- 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/