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SubjectRe: [PATCH 1/3] Kprobes: Make kprobe modules more portable
On Mon, Aug 07, 2006 at 05:25:37PM +0530, Ananth N Mavinakayanahalli wrote:
> From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
>
> This patch introduces KPROBE_ADDR, a macro that abstracts out the
> architecture-specific artefacts of getting the correct text address
> given a symbol. While we are at it, also introduce the symbol_name field
> in struct kprobe to allow for users to just specify the address to be
> probed in terms of the kernel symbol. In-kernel kprobes infrastructure
> decodes the actual text address to probe. The symbol resolution happens
> only if the kprobe.addr isn't explicitly specified.

This change was first mooted by Dave Boutcher during his kprobes
tutorial @ OLS. Thanks Dave! (He had also signed off on the patch)

>
> ---
> Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
> Signed-off-by: Prasanna S.P <prasanna@in.ibm.com>

Acked-by: Dave Boutcher <sleddog@us.ibm.com>

>
>
> ---
> include/asm-powerpc/kprobes.h | 2 ++
> include/linux/kprobes.h | 8 ++++++++
> kernel/kprobes.c | 4 ++++
> 3 files changed, 14 insertions(+)
>
> Index: linux-2.6.18-rc3/include/asm-powerpc/kprobes.h
> ===================================================================
> --- linux-2.6.18-rc3.orig/include/asm-powerpc/kprobes.h
> +++ linux-2.6.18-rc3/include/asm-powerpc/kprobes.h
> @@ -44,6 +44,8 @@ typedef unsigned int kprobe_opcode_t;
> #define IS_TDI(instr) (((instr) & 0xfc000000) == 0x08000000)
> #define IS_TWI(instr) (((instr) & 0xfc000000) == 0x0c000000)
>
> +#define KPROBE_ADDR(name) *((kprobe_opcode_t **)(kallsyms_lookup_name(name)))
> +
> #define JPROBE_ENTRY(pentry) (kprobe_opcode_t *)((func_descr_t *)pentry)
>
> #define is_trap(instr) (IS_TW(instr) || IS_TD(instr) || \
> Index: linux-2.6.18-rc3/include/linux/kprobes.h
> ===================================================================
> --- linux-2.6.18-rc3.orig/include/linux/kprobes.h
> +++ linux-2.6.18-rc3/include/linux/kprobes.h
> @@ -36,6 +36,7 @@
> #include <linux/spinlock.h>
> #include <linux/rcupdate.h>
> #include <linux/mutex.h>
> +#include <linux/kallsyms.h>
>
> #ifdef CONFIG_KPROBES
> #include <asm/kprobes.h>
> @@ -49,6 +50,10 @@
> /* Attach to insert probes on any functions which should be ignored*/
> #define __kprobes __attribute__((__section__(".kprobes.text")))
>
> +#ifndef KPROBE_ADDR /* powerpc has its own definition */
> +#define KPROBE_ADDR(name) (kprobe_opcode_t *)(kallsyms_lookup_name(name))
> +#endif /* KPROBE_ADDR */
> +
> struct kprobe;
> struct pt_regs;
> struct kretprobe;
> @@ -77,6 +82,9 @@ struct kprobe {
> /* location of the probe point */
> kprobe_opcode_t *addr;
>
> + /* Allow user to indicate symbol name of the probe point */
> + char *symbol_name;
> +
> /* Called before addr is executed. */
> kprobe_pre_handler_t pre_handler;
>
> Index: linux-2.6.18-rc3/kernel/kprobes.c
> ===================================================================
> --- linux-2.6.18-rc3.orig/kernel/kprobes.c
> +++ linux-2.6.18-rc3/kernel/kprobes.c
> @@ -446,6 +446,10 @@ static int __kprobes __register_kprobe(s
> struct kprobe *old_p;
> struct module *probed_mod;
>
> + /* Do the kallsyms lookup only if p->addr == NULL */
> + if (!p->addr && (p->symbol_name))
> + p->addr = KPROBE_ADDR(p->symbol_name);
> +
> if ((!kernel_text_address((unsigned long) p->addr)) ||
> in_kprobes_functions((unsigned long) p->addr))
> return -EINVAL;
-
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