Re: [1/6 PATCH] Kprobes : Prevent possible race conditions genericchanges

[Andrew Morton]

Prasanna S Panchamukhi <prasanna@xxxxxxxxxx> wrote:
>
> There are possible race conditions if probes are placed on routines within the
> kprobes files and routines used by the kprobes.

So...  don't do that then?  Is it likely that anyone would want to stick a
probe on the kprobe code itself?

> -kprobe_opcode_t *get_insn_slot(void)
> +kprobe_opcode_t * __kprobes get_insn_slot(void)

coding style regression...

> -int register_kprobe(struct kprobe *p)
> +static int __kprobes in_kprobes_functions(unsigned long addr)
> +{
> +	/* Linker adds these: start and end of __kprobes functions */
> +	extern char __kprobes_text_start[], __kprobes_text_end[];

There's an old unix convention that section markers (start, end, edata,
etc) are declared `int'.  For some reason we don't do that in the kernel. 
Oh well.

> +	if ((ret = in_kprobes_functions((unsigned long) p->addr)) !=0)

whitespace broke.

Some people don't like the assign-then-test-it style.

> +		return ret;
>  	if ((ret = arch_prepare_kprobe(p)) != 0) {
>  		goto rm_kprobe;
>  	}

hm, who put the unneeded braces in there?

> --- linux-2.6.13-rc1-mm1/include/linux/kprobes.h~kprobes-exclude-functions-generic	2005-07-06 18:51:16.000000000 +0530
> +++ linux-2.6.13-rc1-mm1-prasanna/include/linux/kprobes.h	2005-07-06 18:51:16.000000000 +0530
> @@ -42,6 +42,10 @@
>  #define KPROBE_REENTER		0x00000004
>  #define KPROBE_HIT_SSDONE	0x00000008
>  
> +/* Attach to insert probes on any functions which should be ignored*/
> +#define __kprobes	__attribute__((__section__(".kprobes.text")))
> +/* Is this address in the __kprobes functions? */
> +

What's that comment mean?


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