Re: [PATCH][2.5.47]Add exported valid_kernel_address()

Re: [PATCH][2.5.47]Add exported valid_kernel_address()

[Andi Kleen]

Arjan van de Ven <arjanv@redhat.com> writes:

> it is customary that people who ask for an export explain why they need
> it.... would you mind explaining that ?

For modular lkcd I guess. Make a lot of sense to do it modular.

-Andi

Re: [PATCH][2.5.47]Add exported valid_kernel_address()

[Rusty Lynch]

I had a need for it in a sample kprobes driver where I wanted to verify that
some address
was a valid kernel space address before I handed a probe to kprobes.

So I would do something like:

if (!valid_kernel_address(probe->addr)) {
    ret = -EINVAL;
    goto out;
}

register_kprobe(probe);

and then kpboes will go and attempt to set *(probe->addr) = BREAK_POINT;

    -rustyl
----- Original Message -----
From: "Andi Kleen" <ak@suse.de>
To: "Arjan van de Ven" <arjanv@redhat.com>
Cc: <linux-kernel@vger.kernel.org>; <rusty@linux.co.intel.com>
Sent: Wednesday, November 13, 2002 1:14 PM
Subject: Re: [PATCH][2.5.47]Add exported valid_kernel_address()


> Arjan van de Ven <arjanv@redhat.com> writes:
>
> > it is customary that people who ask for an export explain why they need
> > it.... would you mind explaining that ?
>
> For modular lkcd I guess. Make a lot of sense to do it modular.
>
> -Andi

Re: [PATCH][2.5.47]Add exported valid_kernel_address()

[Rusty Lynch]

To clarify further, I am talking about the sample driver I submitted earlier
at
http://marc.theaimsgroup.com/?l=linux-kernel&m=103721364225087&w=2

The patch implements a char device that enables arbitrary printk's to be
inserted at in arbitrary kernel addresses.  It is used by writing strings of
the
form "0xADDRESS MESSAGE" to the device.

I was looking for a way to verify the address passed in was valid before
creating and inserting a new probe.

Maybe there is a better way to verify a kernel address is valid before
messing
with it?

    -rusty
----- Original Message -----
From: "Rusty Lynch" <rusty@linux.co.intel.com>
To: "Arjan van de Ven" <arjanv@redhat.com>; "Andi Kleen" <ak@suse.de>
Cc: <linux-kernel@vger.kernel.org>; <rusty@linux.co.intel.com>
Sent: Wednesday, November 13, 2002 1:24 PM
Subject: Re: [PATCH][2.5.47]Add exported valid_kernel_address()


> I had a need for it in a sample kprobes driver where I wanted to verify
that
> some address
> was a valid kernel space address before I handed a probe to kprobes.
>
> So I would do something like:
>
> if (!valid_kernel_address(probe->addr)) {
>     ret = -EINVAL;
>     goto out;
> }
>
> register_kprobe(probe);
>
> and then kpboes will go and attempt to set *(probe->addr) = BREAK_POINT;
>
>     -rustyl
> ----- Original Message -----
> From: "Andi Kleen" <ak@suse.de>
> To: "Arjan van de Ven" <arjanv@redhat.com>
> Cc: <linux-kernel@vger.kernel.org>; <rusty@linux.co.intel.com>
> Sent: Wednesday, November 13, 2002 1:14 PM
> Subject: Re: [PATCH][2.5.47]Add exported valid_kernel_address()
>
>
> > Arjan van de Ven <arjanv@redhat.com> writes:
> >
> > > it is customary that people who ask for an export explain why they
need
> > > it.... would you mind explaining that ?
> >
> > For modular lkcd I guess. Make a lot of sense to do it modular.
> >
> > -Andi
>
> -
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[PATCH][2.5.47]Add exported valid_kernel_address()

[Rusty Lynch]

The following is a small patch to the 2.5.47 kernel that adds an exported
function called valid_kernel_address() that allows kernel code to verify
a kernel-mapped address is valid.

valid_kernel_address just calls the static inline kernel_text_address()
function defined in arch/i386/kernel/traps.c 

	   -rustyl

diff -urN linux-2.5.47/arch/i386/kernel/i386_ksyms.c linux-2.5.47-vka-patch/arch/i386/kernel/i386_ksyms.c
--- linux-2.5.47/arch/i386/kernel/i386_ksyms.c	2002-11-10 19:28:32.000000000 -0800
+++ linux-2.5.47-vka-patch/arch/i386/kernel/i386_ksyms.c	2002-11-13 11:46:49.000000000 -0800
@@ -59,6 +59,8 @@
 extern unsigned long cpu_khz;
 extern unsigned long get_cmos_time(void);
 
+extern int valid_kernel_address(unsigned long addr);
+
 /* platform dependent support */
 EXPORT_SYMBOL(boot_cpu_data);
 #ifdef CONFIG_EISA
@@ -91,6 +93,7 @@
 EXPORT_SYMBOL(get_cmos_time);
 EXPORT_SYMBOL(cpu_khz);
 EXPORT_SYMBOL(apm_info);
+EXPORT_SYMBOL(valid_kernel_address);
 
 #ifdef CONFIG_DEBUG_IOVIRT
 EXPORT_SYMBOL(__io_virt_debug);
diff -urN linux-2.5.47/arch/i386/kernel/traps.c linux-2.5.47-vka-patch/arch/i386/kernel/traps.c
--- linux-2.5.47/arch/i386/kernel/traps.c	2002-11-10 19:28:05.000000000 -0800
+++ linux-2.5.47-vka-patch/arch/i386/kernel/traps.c	2002-11-13 11:51:58.000000000 -0800
@@ -129,6 +129,11 @@
 
 #endif
 
+int valid_kernel_address(unsigned long addr)
+{
+	return kernel_text_address(addr);
+}
+
 void show_trace(unsigned long * stack)
 {
 	int i;

Re: [PATCH][2.5.47]Add exported valid_kernel_address()

[Arjan van de Ven]

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On Wed, 2002-11-13 at 21:13, Rusty Lynch wrote:
> The following is a small patch to the 2.5.47 kernel that adds an exported
> function called valid_kernel_address() that allows kernel code to verify
> a kernel-mapped address is valid.
> 
> valid_kernel_address just calls the static inline kernel_text_address()
> function defined in arch/i386/kernel/traps.c 
> 
it is customary that people who ask for an export explain why they need
it.... would you mind explaining that ?


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