lkml.org 
[lkml]   [2017]   [Jul]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH -tip v4] [BUGFIX] kprobes/x86: Do not jump-optimize kprobes on irq entry code
On Thu, 27 Jul 2017 10:24:46 +0200
Ingo Molnar <mingo@kernel.org> wrote:

>
> * Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > Since the kernel segment registers are not prepared at the
> > entry of irq-entry code, if a kprobe on such code is
> > jump-optimized, accessing per-cpu variables may cause
> > kernel panic.
> > However, if the kprobe is not optimized, it kicks int3
> > exception and set segment registers correctly.
> >
> > This checks probe-address and if it is in irq-entry code,
> > it prohibits optimizing such kprobes. This means we can
> > continuously probing such interrupt handlers by kprobes
> > but it is not optimized anymore.
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > Reported-by: Francis Deslauriers <francis.deslauriers@efficios.com>
> > Tested-by: Francis Deslauriers <francis.deslauriers@efficios.com>
> > ---
> > Changes in v4:
> > - Fix to use CONFIG_OPTPROBES instead of CONFIG_KPROBES.
> > ---
> > arch/x86/kernel/kprobes/opt.c | 9 ++++++---
> > include/asm-generic/vmlinux.lds.h | 6 ++++--
> > include/linux/interrupt.h | 3 ++-
> > 3 files changed, 12 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
> > index 69ea0bc..c26e7f9 100644
> > --- a/arch/x86/kernel/kprobes/opt.c
> > +++ b/arch/x86/kernel/kprobes/opt.c
> > @@ -29,6 +29,7 @@
> > #include <linux/kallsyms.h>
> > #include <linux/ftrace.h>
> > #include <linux/frame.h>
> > +#include <linux/interrupt.h>
> >
> > #include <asm/text-patching.h>
> > #include <asm/cacheflush.h>
> > @@ -251,10 +252,12 @@ static int can_optimize(unsigned long paddr)
> >
> > /*
> > * Do not optimize in the entry code due to the unstable
> > - * stack handling.
> > + * stack handling and registers setup.
> > */
> > - if ((paddr >= (unsigned long)__entry_text_start) &&
> > - (paddr < (unsigned long)__entry_text_end))
> > + if (((paddr >= (unsigned long)__entry_text_start) &&
> > + (paddr < (unsigned long)__entry_text_end)) ||
> > + ((paddr >= (unsigned long)__irqentry_text_start) &&
> > + (paddr < (unsigned long)__irqentry_text_end)))
> > return 0;
> >
> > /* Check there is enough space for a relative jump. */
> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> > index da0be9a..3092a1f 100644
> > --- a/include/asm-generic/vmlinux.lds.h
> > +++ b/include/asm-generic/vmlinux.lds.h
> > @@ -483,7 +483,8 @@
> > *(.entry.text) \
> > VMLINUX_SYMBOL(__entry_text_end) = .;
> >
> > -#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
> > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || \
> > + defined(CONFIG_OPTPROBES)
> > #define IRQENTRY_TEXT \
> > ALIGN_FUNCTION(); \
> > VMLINUX_SYMBOL(__irqentry_text_start) = .; \
> > @@ -493,7 +494,8 @@
> > #define IRQENTRY_TEXT
> > #endif
> >
> > -#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
> > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || \
> > + defined(CONFIG_OPTPROBES)
> > #define SOFTIRQENTRY_TEXT \
> > ALIGN_FUNCTION(); \
> > VMLINUX_SYMBOL(__softirqentry_text_start) = .; \
> > diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> > index a2fdddd..f95b046 100644
> > --- a/include/linux/interrupt.h
> > +++ b/include/linux/interrupt.h
> > @@ -726,7 +726,8 @@ extern int early_irq_init(void);
> > extern int arch_probe_nr_irqs(void);
> > extern int arch_early_irq_init(void);
> >
> > -#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN)
> > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_KASAN) || \
> > + defined(CONFIG_OPTPROBES)
>
> Please split the generic changes to asm-generic/vmlinux.lds.h and interrupt.h into
> a separate patch, with its own changelog, because this is not a kprobes/x86 only
> patch anymore.

OK. BTW, I think it is a good time to make a new (hidden) Kconfig entry for
irqentry, like CONFIG_IRQENTRY and above 3 configs select it. What would
you think?

Thank you,

>
> Thanks,
>
> Ingo


--
Masami Hiramatsu <mhiramat@kernel.org>

\
 
 \ /
  Last update: 2017-07-27 15:21    [W:0.055 / U:65.344 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site