lkml.org 
[lkml]   [2011]   [Feb]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] kprobes - do not allow optimized kprobes in entry code
(2011/02/16 2:05), Jiri Olsa wrote:
> 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.

Agreed, and this could be the best way, because kprobes can not
know where the kernel stack is ready without this text section.

>
> wbr,
> jirka
>
>
> Signed-off-by: Jiri Olsa <jolsa@redhat.com>

Looks good for me :)

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

> ---
> 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(); \


--
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com


\
 
 \ /
  Last update: 2011-02-16 04:39    [from the cache]
©2003-2011 Jasper Spaans