* [PATCH] kprobes: x86: mark 2 bytes NOP as boostable.
@ 2015-02-09 12:45 Wang Nan
2015-02-09 23:34 ` Masami Hiramatsu
0 siblings, 1 reply; 5+ messages in thread
From: Wang Nan @ 2015-02-09 12:45 UTC (permalink / raw)
To: masami.hiramatsu.pt, tglx, mingo, x86; +Cc: linux-kernel, lizefan
x86 kprobes is unable to probe at 2 bytes nop like:
nopl 0x0(%rax,%rax,1)
which is 0x0f 0x1f 0x44 0x00 0x00.
Such nops have exactly 5 bytes which is able to hold a relative jmp
instruction. Boosting them should be obviously safe.
This patch enable boosting such nops by simply updating
twobyte_is_boostable[] array.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
arch/x86/kernel/kprobes/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 98f654d..6a1146e 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -84,7 +84,7 @@ static volatile u32 twobyte_is_boostable[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
- W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */
+ W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
--
1.8.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] kprobes: x86: mark 2 bytes NOP as boostable.
2015-02-09 12:45 [PATCH] kprobes: x86: mark 2 bytes NOP as boostable Wang Nan
@ 2015-02-09 23:34 ` Masami Hiramatsu
2015-02-10 1:34 ` [PATCH][RESEND] " Wang Nan
0 siblings, 1 reply; 5+ messages in thread
From: Masami Hiramatsu @ 2015-02-09 23:34 UTC (permalink / raw)
To: Wang Nan; +Cc: tglx, mingo, x86, linux-kernel, lizefan
(2015/02/09 21:45), Wang Nan wrote:
> x86 kprobes is unable to probe at 2 bytes nop like:
^^^^^ boost
>
> nopl 0x0(%rax,%rax,1)
>
> which is 0x0f 0x1f 0x44 0x00 0x00.
>
> Such nops have exactly 5 bytes which is able to hold a relative jmp
> instruction. Boosting them should be obviously safe.
>
> This patch enable boosting such nops by simply updating
> twobyte_is_boostable[] array.
Anyway, this looks good to me.
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Thank you!
>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> ---
> arch/x86/kernel/kprobes/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> index 98f654d..6a1146e 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -84,7 +84,7 @@ static volatile u32 twobyte_is_boostable[256 / 32] = {
> /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
> /* ---------------------------------------------- */
> W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
> - W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */
> + W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
> W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
> W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
> W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
>
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH][RESEND] kprobes: x86: mark 2 bytes NOP as boostable.
2015-02-09 23:34 ` Masami Hiramatsu
@ 2015-02-10 1:34 ` Wang Nan
2015-02-11 4:18 ` Wang Nan
2015-02-19 0:26 ` [tip:perf/urgent] kprobes/x86: Mark " tip-bot for Wang Nan
0 siblings, 2 replies; 5+ messages in thread
From: Wang Nan @ 2015-02-10 1:34 UTC (permalink / raw)
To: masami.hiramatsu.pt, mingo; +Cc: tglx, x86, linux-kernel, lizefan
Currently, x86 kprobes is unable to boost 2 bytes nop like:
nopl 0x0(%rax,%rax,1)
which is 0x0f 0x1f 0x44 0x00 0x00.
Such nops have exactly 5 bytes to hold a relative jmp instruction.
Boosting them should be obviously safe.
This patch enable boosting such nops by simply updating
twobyte_is_boostable[] array.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
arch/x86/kernel/kprobes/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 98f654d..6a1146e 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -84,7 +84,7 @@ static volatile u32 twobyte_is_boostable[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
- W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */
+ W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
--
1.8.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH][RESEND] kprobes: x86: mark 2 bytes NOP as boostable.
2015-02-10 1:34 ` [PATCH][RESEND] " Wang Nan
@ 2015-02-11 4:18 ` Wang Nan
2015-02-19 0:26 ` [tip:perf/urgent] kprobes/x86: Mark " tip-bot for Wang Nan
1 sibling, 0 replies; 5+ messages in thread
From: Wang Nan @ 2015-02-11 4:18 UTC (permalink / raw)
To: Andrew Morton
Cc: masami.hiramatsu.pt, mingo, tglx, x86, linux-kernel, lizefan
Hi Andrew,
Could you please queue this patch onto your -mm tree? Masami has given an Acked-by already.
Thank you!
On 2015/2/10 9:34, Wang Nan wrote:
> Currently, x86 kprobes is unable to boost 2 bytes nop like:
>
> nopl 0x0(%rax,%rax,1)
>
> which is 0x0f 0x1f 0x44 0x00 0x00.
>
> Such nops have exactly 5 bytes to hold a relative jmp instruction.
> Boosting them should be obviously safe.
>
> This patch enable boosting such nops by simply updating
> twobyte_is_boostable[] array.
>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> ---
> arch/x86/kernel/kprobes/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> index 98f654d..6a1146e 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -84,7 +84,7 @@ static volatile u32 twobyte_is_boostable[256 / 32] = {
> /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
> /* ---------------------------------------------- */
> W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
> - W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */
> + W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
> W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
> W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
> W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* [tip:perf/urgent] kprobes/x86: Mark 2 bytes NOP as boostable
2015-02-10 1:34 ` [PATCH][RESEND] " Wang Nan
2015-02-11 4:18 ` Wang Nan
@ 2015-02-19 0:26 ` tip-bot for Wang Nan
1 sibling, 0 replies; 5+ messages in thread
From: tip-bot for Wang Nan @ 2015-02-19 0:26 UTC (permalink / raw)
To: linux-tip-commits
Cc: wangnan0, lizefan, masami.hiramatsu.pt, mingo, linux-kernel, tglx,
hpa
Commit-ID: b7e37567d080301d38a302bb93ba79d1ca446dca
Gitweb: http://git.kernel.org/tip/b7e37567d080301d38a302bb93ba79d1ca446dca
Author: Wang Nan <wangnan0@huawei.com>
AuthorDate: Tue, 10 Feb 2015 09:34:05 +0800
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 18 Feb 2015 21:50:12 +0100
kprobes/x86: Mark 2 bytes NOP as boostable
Currently, x86 kprobes is unable to boost 2 bytes nop like:
nopl 0x0(%rax,%rax,1)
which is 0x0f 0x1f 0x44 0x00 0x00.
Such nops have exactly 5 bytes to hold a relative jmp
instruction. Boosting them should be obviously safe.
This patch enable boosting such nops by simply updating
twobyte_is_boostable[] array.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: <lizefan@huawei.com>
Link: http://lkml.kernel.org/r/1423532045-41049-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/kprobes/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 98f654d..6a1146e 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -84,7 +84,7 @@ static volatile u32 twobyte_is_boostable[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
- W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */
+ W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */
W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
^ permalink raw reply related [flat|nested] 5+ messages in thread
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2015-02-09 12:45 [PATCH] kprobes: x86: mark 2 bytes NOP as boostable Wang Nan
2015-02-09 23:34 ` Masami Hiramatsu
2015-02-10 1:34 ` [PATCH][RESEND] " Wang Nan
2015-02-11 4:18 ` Wang Nan
2015-02-19 0:26 ` [tip:perf/urgent] kprobes/x86: Mark " tip-bot for Wang Nan
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