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    Subject[PATCH 1/3] Kprobes: Make kprobe modules more portable
    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.

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