2022-09-17 02:30:51

by Yipeng Zou

Subject: [PATCH 0/2] make weak attributes in {k,u}probes

We have some function implementation under some arch does nothing.
We can mark it with weak attributes to improve.
1. arch_init_kprobes in kprobes
2. arch_uprobe_exception_notify in uprobes

Yipeng Zou (2):
kprobes: make arch_init_kprobes as weak
uprobes: make arch_uprobe_exception_notify as weak

arch/arm/probes/uprobes/core.c | 6 ------
arch/arm64/kernel/probes/uprobes.c | 6 ------
arch/csky/kernel/probes/kprobes.c | 5 -----
arch/csky/kernel/probes/uprobes.c | 6 ------
arch/riscv/kernel/probes/kprobes.c | 5 -----
arch/riscv/kernel/probes/uprobes.c | 6 ------
arch/s390/kernel/kprobes.c | 5 -----
arch/x86/kernel/kprobes/core.c | 5 -----
kernel/events/uprobes.c | 6 ++++++
kernel/kprobes.c | 5 +++++
10 files changed, 11 insertions(+), 44 deletions(-)

--
2.17.1

2022-09-17 02:33:13

by Yipeng Zou

Subject: [PATCH 2/2] uprobes: make arch_uprobe_exception_notify as weak

The function implementation under some arch does nothing.
We can mark it with weak attributes to improve.

Signed-off-by: Yipeng Zou <[email protected]>
---
arch/arm/probes/uprobes/core.c | 6 ------
arch/arm64/kernel/probes/uprobes.c | 6 ------
arch/csky/kernel/probes/uprobes.c | 6 ------
arch/riscv/kernel/probes/uprobes.c | 6 ------
kernel/events/uprobes.c | 6 ++++++
5 files changed, 6 insertions(+), 24 deletions(-)

diff --git a/arch/arm/probes/uprobes/core.c b/arch/arm/probes/uprobes/core.c
index f5f790c6e5f8..535ea1b355ed 100644
--- a/arch/arm/probes/uprobes/core.c
+++ b/arch/arm/probes/uprobes/core.c
@@ -175,12 +175,6 @@ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
instruction_pointer_set(regs, utask->vaddr);
}

-int arch_uprobe_exception_notify(struct notifier_block *self,
- unsigned long val, void *data)
-{
- return NOTIFY_DONE;
-}
-
static int uprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
{
unsigned long flags;
diff --git a/arch/arm64/kernel/probes/uprobes.c b/arch/arm64/kernel/probes/uprobes.c
index d49aef2657cd..687ede3375a6 100644
--- a/arch/arm64/kernel/probes/uprobes.c
+++ b/arch/arm64/kernel/probes/uprobes.c
@@ -159,12 +159,6 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
return orig_ret_vaddr;
}

-int arch_uprobe_exception_notify(struct notifier_block *self,
- unsigned long val, void *data)
-{
- return NOTIFY_DONE;
-}
-
static int uprobe_breakpoint_handler(struct pt_regs *regs,
unsigned long esr)
{
diff --git a/arch/csky/kernel/probes/uprobes.c b/arch/csky/kernel/probes/uprobes.c
index 2d31a12e46cf..67ff13d960e8 100644
--- a/arch/csky/kernel/probes/uprobes.c
+++ b/arch/csky/kernel/probes/uprobes.c
@@ -132,12 +132,6 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
return ra;
}

-int arch_uprobe_exception_notify(struct notifier_block *self,
- unsigned long val, void *data)
-{
- return NOTIFY_DONE;
-}
-
int uprobe_breakpoint_handler(struct pt_regs *regs)
{
if (uprobe_pre_sstep_notifier(regs))
diff --git a/arch/riscv/kernel/probes/uprobes.c b/arch/riscv/kernel/probes/uprobes.c
index c976a21cd4bd..770f16c6e00f 100644
--- a/arch/riscv/kernel/probes/uprobes.c
+++ b/arch/riscv/kernel/probes/uprobes.c
@@ -131,12 +131,6 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
return ra;
}

-int arch_uprobe_exception_notify(struct notifier_block *self,
- unsigned long val, void *data)
-{
- return NOTIFY_DONE;
-}
-
bool uprobe_breakpoint_handler(struct pt_regs *regs)
{
if (uprobe_pre_sstep_notifier(regs))
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index d9e357b7e17c..33e637f7a202 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -2343,6 +2343,12 @@ int uprobe_post_sstep_notifier(struct pt_regs *regs)
return 1;
}

+int __weak arch_uprobe_exception_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ return NOTIFY_DONE;
+}
+
static struct notifier_block uprobe_exception_nb = {
.notifier_call = arch_uprobe_exception_notify,
.priority = INT_MAX-1, /* notified after kprobes, kgdb */
--
2.17.1

2022-09-17 11:21:05

by Guo Ren

Subject: Re: [PATCH 0/2] make weak attributes in {k,u}probes

It's a riskless cleanup.

Acked-by: Guo Ren <[email protected]>

On Sat, Sep 17, 2022 at 9:59 AM Yipeng Zou <[email protected]> wrote:
>
> We have some function implementation under some arch does nothing.
> We can mark it with weak attributes to improve.
> 1. arch_init_kprobes in kprobes
> 2. arch_uprobe_exception_notify in uprobes
>
> Yipeng Zou (2):
> kprobes: make arch_init_kprobes as weak
> uprobes: make arch_uprobe_exception_notify as weak
>
> arch/arm/probes/uprobes/core.c | 6 ------
> arch/arm64/kernel/probes/uprobes.c | 6 ------
> arch/csky/kernel/probes/kprobes.c | 5 -----
> arch/csky/kernel/probes/uprobes.c | 6 ------
> arch/riscv/kernel/probes/kprobes.c | 5 -----
> arch/riscv/kernel/probes/uprobes.c | 6 ------
> arch/s390/kernel/kprobes.c | 5 -----
> arch/x86/kernel/kprobes/core.c | 5 -----
> kernel/events/uprobes.c | 6 ++++++
> kernel/kprobes.c | 5 +++++
> 10 files changed, 11 insertions(+), 44 deletions(-)
>
> --
> 2.17.1
>


--
Best Regards
Guo Ren

2022-09-20 17:35:53

by Naveen N. Rao

Subject: Re: [PATCH 0/2] make weak attributes in {k,u}probes

Yipeng Zou wrote:
> We have some function implementation under some arch does nothing.
> We can mark it with weak attributes to improve.

That's not always an improvement. See [1] for an example, among many
other patches to reduce use of __weak functions in the kernel.

As an alternative, please consider the approach used in [1].


- Naveen

[1] https://lore.kernel.org/all/[email protected]/

2022-09-21 09:10:23

by Peter Zijlstra

Subject: Re: [PATCH 0/2] make weak attributes in {k,u}probes

On Tue, Sep 20, 2022 at 10:32:46PM +0530, Naveen N. Rao wrote:
> Yipeng Zou wrote:
> > We have some function implementation under some arch does nothing.
> > We can mark it with weak attributes to improve.
>
> That's not always an improvement. See [1] for an example, among many other
> patches to reduce use of __weak functions in the kernel.

More weak 'fun':

https://lkml.kernel.org/r/[email protected]