Re: [PATCH -tip v2 2/2] [BUGFIX] kprobes/x86: Check Interrupt Flag modifier when registering probe
On Thu, Mar 14, 2013 at 08:52:43PM +0900, Masami Hiramatsu wrote: > Currently kprobes check whether the copied instruction modifies > IF (interrupt flag) on each probe hit. This means not only > introducing overhead but also involving inat_get_opcode_attribute > into kprobes hot path, and it can cause an infinit recursive > call (and kernel panic in the end). > > Actually, since the copied instruction itself never be modified > on the buffer, it is needless to analyze the instruction every > probe hit. > > To fix this issue, we checks it only once when registering probe > and store the result on ainsn->if_modifier. > > Signed-off-by: Masami Hiramatsu > Reported-by: Timo Juhani Lindfors > Cc: "David S. Miller" > Cc: Ananth N Mavinakayanahalli > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: "H. Peter Anvin" > Cc: Steven Rostedt > Cc: Linus Torvalds Acked-by: Ananth N Mavinakayanahalli -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH -tip v2 2/2] [BUGFIX] kprobes/x86: Check Interrupt Flag modifier when registering probe
Currently kprobes check whether the copied instruction modifies
IF (interrupt flag) on each probe hit. This means not only
introducing overhead but also involving inat_get_opcode_attribute
into kprobes hot path, and it can cause an infinit recursive
call (and kernel panic in the end).
Actually, since the copied instruction itself never be modified
on the buffer, it is needless to analyze the instruction every
probe hit.
To fix this issue, we checks it only once when registering probe
and store the result on ainsn->if_modifier.
Signed-off-by: Masami Hiramatsu
Reported-by: Timo Juhani Lindfors
Cc: "David S. Miller"
Cc: Ananth N Mavinakayanahalli
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: "H. Peter Anvin"
Cc: Steven Rostedt
Cc: Linus Torvalds
---
arch/x86/include/asm/kprobes.h |1 +
arch/x86/kernel/kprobes/core.c |5 -
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
index d3ddd17..5a6d287 100644
--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -77,6 +77,7 @@ struct arch_specific_insn {
* a post_handler or break_handler).
*/
int boostable;
+ bool if_modifier;
};
struct arch_optimized_insn {
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 3f06e61..7bfe318 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -375,6 +375,9 @@ static void __kprobes arch_copy_kprobe(struct kprobe *p)
else
p->ainsn.boostable = -1;
+ /* Check whether the instruction modifies Interrupt Flag or not */
+ p->ainsn.if_modifier = is_IF_modifier(p->ainsn.insn);
+
/* Also, displacement change doesn't affect the first byte */
p->opcode = p->ainsn.insn[0];
}
@@ -434,7 +437,7 @@ static void __kprobes set_current_kprobe(struct kprobe *p,
struct pt_regs *regs,
__this_cpu_write(current_kprobe, p);
kcb->kprobe_saved_flags = kcb->kprobe_old_flags
= (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
- if (is_IF_modifier(p->ainsn.insn))
+ if (p->ainsn.if_modifier)
kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF;
}
--
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[PATCH -tip v2 2/2] [BUGFIX] kprobes/x86: Check Interrupt Flag modifier when registering probe
Currently kprobes check whether the copied instruction modifies
IF (interrupt flag) on each probe hit. This means not only
introducing overhead but also involving inat_get_opcode_attribute
into kprobes hot path, and it can cause an infinit recursive
call (and kernel panic in the end).
Actually, since the copied instruction itself never be modified
on the buffer, it is needless to analyze the instruction every
probe hit.
To fix this issue, we checks it only once when registering probe
and store the result on ainsn-if_modifier.
Signed-off-by: Masami Hiramatsu masami.hiramatsu...@hitachi.com
Reported-by: Timo Juhani Lindfors timo.lindf...@iki.fi
Cc: David S. Miller da...@davemloft.net
Cc: Ananth N Mavinakayanahalli ana...@in.ibm.com
Cc: Thomas Gleixner t...@linutronix.de
Cc: Ingo Molnar mi...@redhat.com
Cc: H. Peter Anvin h...@zytor.com
Cc: Steven Rostedt rost...@goodmis.org
Cc: Linus Torvalds torva...@linux-foundation.org
---
arch/x86/include/asm/kprobes.h |1 +
arch/x86/kernel/kprobes/core.c |5 -
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
index d3ddd17..5a6d287 100644
--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -77,6 +77,7 @@ struct arch_specific_insn {
* a post_handler or break_handler).
*/
int boostable;
+ bool if_modifier;
};
struct arch_optimized_insn {
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 3f06e61..7bfe318 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -375,6 +375,9 @@ static void __kprobes arch_copy_kprobe(struct kprobe *p)
else
p-ainsn.boostable = -1;
+ /* Check whether the instruction modifies Interrupt Flag or not */
+ p-ainsn.if_modifier = is_IF_modifier(p-ainsn.insn);
+
/* Also, displacement change doesn't affect the first byte */
p-opcode = p-ainsn.insn[0];
}
@@ -434,7 +437,7 @@ static void __kprobes set_current_kprobe(struct kprobe *p,
struct pt_regs *regs,
__this_cpu_write(current_kprobe, p);
kcb-kprobe_saved_flags = kcb-kprobe_old_flags
= (regs-flags (X86_EFLAGS_TF | X86_EFLAGS_IF));
- if (is_IF_modifier(p-ainsn.insn))
+ if (p-ainsn.if_modifier)
kcb-kprobe_saved_flags = ~X86_EFLAGS_IF;
}
--
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH -tip v2 2/2] [BUGFIX] kprobes/x86: Check Interrupt Flag modifier when registering probe
On Thu, Mar 14, 2013 at 08:52:43PM +0900, Masami Hiramatsu wrote: Currently kprobes check whether the copied instruction modifies IF (interrupt flag) on each probe hit. This means not only introducing overhead but also involving inat_get_opcode_attribute into kprobes hot path, and it can cause an infinit recursive call (and kernel panic in the end). Actually, since the copied instruction itself never be modified on the buffer, it is needless to analyze the instruction every probe hit. To fix this issue, we checks it only once when registering probe and store the result on ainsn-if_modifier. Signed-off-by: Masami Hiramatsu masami.hiramatsu...@hitachi.com Reported-by: Timo Juhani Lindfors timo.lindf...@iki.fi Cc: David S. Miller da...@davemloft.net Cc: Ananth N Mavinakayanahalli ana...@in.ibm.com Cc: Thomas Gleixner t...@linutronix.de Cc: Ingo Molnar mi...@redhat.com Cc: H. Peter Anvin h...@zytor.com Cc: Steven Rostedt rost...@goodmis.org Cc: Linus Torvalds torva...@linux-foundation.org Acked-by: Ananth N Mavinakayanahalli ana...@in.ibm.com -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
