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Message-ID: <20060809161854.GA13622@infradead.org>
Date: Wed, 9 Aug 2006 17:18:54 +0100
From: Christoph Hellwig <hch@...radead.org>
To: Christoph Hellwig <hch@...radead.org>,
David Smith <dsmith@...hat.com>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
linux-kernel@...r.kernel.org, shemminger@...l.org
Subject: Re: [PATCH 1/3] Kprobes: Make kprobe modules more portable
On Wed, Aug 09, 2006 at 05:10:39PM +0100, Christoph Hellwig wrote:
> On Wed, Aug 09, 2006 at 11:01:45AM -0500, David Smith wrote:
> > > + if (p->symbol_name) {
> > > + if (p->addr)
> > > + return -EINVAL;
> > > + p->addr = kprobe_lookup_name(p->symbol_name) + p->offset;
> > > + }
> >
> > What if kprobe_lookup_name() fails
>
> for that case we need the check in your snipplet below.
>
> > or if CONFIG_KALLSYMS isn't set?
>
> I think we should just disallow that case. having kprobes without kallsyms
> is rather pointless. I'll send a patch to add the dependency to the Kconfig
> files.
Here's an updated version of that patch that a) adds a KALLYMS dependency
and b) adds a check for p->addr. Note that this check is outside the
if (p->symbol_name) block so it also returns EINVAL if the user didn't
specifcy either and address or a symbol name.
Index: linux-2.6/include/asm-powerpc/kprobes.h
===================================================================
--- linux-2.6.orig/include/asm-powerpc/kprobes.h 2006-08-09 13:44:39.000000000 +0200
+++ linux-2.6/include/asm-powerpc/kprobes.h 2006-08-09 13:44:57.000000000 +0200
@@ -44,6 +44,9 @@
#define IS_TDI(instr) (((instr) & 0xfc000000) == 0x08000000)
#define IS_TWI(instr) (((instr) & 0xfc000000) == 0x0c000000)
+#define kprobe_lookup_name(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/include/linux/kprobes.h
===================================================================
--- linux-2.6.orig/include/linux/kprobes.h 2006-08-09 13:44:39.000000000 +0200
+++ linux-2.6/include/linux/kprobes.h 2006-08-09 13:44:57.000000000 +0200
@@ -77,6 +77,12 @@
/* location of the probe point */
kprobe_opcode_t *addr;
+ /* Allow user to indicate symbol name of the probe point */
+ char *symbol_name;
+
+ /* Offset into the symbol */
+ unsigned int offset;
+
/* Called before addr is executed. */
kprobe_pre_handler_t pre_handler;
Index: linux-2.6/kernel/kprobes.c
===================================================================
--- linux-2.6.orig/kernel/kprobes.c 2006-08-09 13:44:39.000000000 +0200
+++ linux-2.6/kernel/kprobes.c 2006-08-09 18:12:47.000000000 +0200
@@ -37,6 +37,7 @@
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/moduleloader.h>
+#include <linux/kallsyms.h>
#include <asm-generic/sections.h>
#include <asm/cacheflush.h>
#include <asm/errno.h>
@@ -45,6 +46,16 @@
#define KPROBE_HASH_BITS 6
#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
+
+/*
+ * Some oddball architectures like 64bit powerpc have function descriptors
+ * so this must be overridable.
+ */
+#ifndef kprobe_lookup_name
+#define kprobe_lookup_name(name) \
+ ((kprobe_opcode_t *)(kallsyms_lookup_name(name))
+#endif
+
static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
static atomic_t kprobe_count;
@@ -447,6 +458,21 @@
struct kprobe *old_p;
struct module *probed_mod;
+ /*
+ * If we have a symbol_name argument look it up,
+ * and add it to the address. That way the addr
+ * field can either be global or relative to a symbol.
+ */
+ if (p->symbol_name) {
+ if (p->addr)
+ return -EINVAL;
+ p->addr = kprobe_lookup_name(p->symbol_name);
+ }
+
+ if (!p->addr)
+ return -EINVAL;
+ p->addr += p->offset;
+
if ((!kernel_text_address((unsigned long) p->addr)) ||
in_kprobes_functions((unsigned long) p->addr))
return -EINVAL;
Index: linux-2.6/kernel/kallsyms.c
===================================================================
--- linux-2.6.orig/kernel/kallsyms.c 2006-08-09 13:44:39.000000000 +0200
+++ linux-2.6/kernel/kallsyms.c 2006-08-09 13:44:57.000000000 +0200
@@ -154,7 +154,6 @@
}
return module_kallsyms_lookup_name(name);
}
-EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
/*
* Lookup an address
Index: linux-2.6/net/ipv4/tcp_probe.c
===================================================================
--- linux-2.6.orig/net/ipv4/tcp_probe.c 2006-08-09 13:44:39.000000000 +0200
+++ linux-2.6/net/ipv4/tcp_probe.c 2006-08-09 13:44:57.000000000 +0200
@@ -99,8 +99,10 @@
}
static struct jprobe tcp_send_probe = {
- .kp = { .addr = (kprobe_opcode_t *) &tcp_sendmsg, },
- .entry = (kprobe_opcode_t *) &jtcp_sendmsg,
+ .kp = {
+ .symbol_name = "tcp_sendmsg",
+ },
+ .entry = JPROBE_ENTRY(jtcp_sendmsg),
};
Index: linux-2.6/arch/i386/Kconfig
===================================================================
--- linux-2.6.orig/arch/i386/Kconfig 2006-08-08 17:13:13.000000000 +0200
+++ linux-2.6/arch/i386/Kconfig 2006-08-09 18:13:59.000000000 +0200
@@ -1129,7 +1129,7 @@
config KPROBES
bool "Kprobes (EXPERIMENTAL)"
- depends on EXPERIMENTAL && MODULES
+ depends on KALLSYMS && EXPERIMENTAL && MODULES
help
Kprobes allows you to trap at almost any kernel address and
execute a callback function. register_kprobe() establishes
Index: linux-2.6/arch/ia64/Kconfig
===================================================================
--- linux-2.6.orig/arch/ia64/Kconfig 2006-08-08 17:13:13.000000000 +0200
+++ linux-2.6/arch/ia64/Kconfig 2006-08-09 18:14:13.000000000 +0200
@@ -510,7 +510,7 @@
config KPROBES
bool "Kprobes (EXPERIMENTAL)"
- depends on EXPERIMENTAL && MODULES
+ depends on KALLSYMS && EXPERIMENTAL && MODULES
help
Kprobes allows you to trap at almost any kernel address and
execute a callback function. register_kprobe() establishes
Index: linux-2.6/arch/powerpc/Kconfig
===================================================================
--- linux-2.6.orig/arch/powerpc/Kconfig 2006-08-08 17:13:13.000000000 +0200
+++ linux-2.6/arch/powerpc/Kconfig 2006-08-09 18:15:00.000000000 +0200
@@ -1045,7 +1045,7 @@
config KPROBES
bool "Kprobes (EXPERIMENTAL)"
- depends on PPC64 && EXPERIMENTAL && MODULES
+ depends on PPC64 && KALLSYMS && EXPERIMENTAL && MODULES
help
Kprobes allows you to trap at almost any kernel address and
execute a callback function. register_kprobe() establishes
Index: linux-2.6/arch/sparc64/Kconfig
===================================================================
--- linux-2.6.orig/arch/sparc64/Kconfig 2006-08-08 17:13:13.000000000 +0200
+++ linux-2.6/arch/sparc64/Kconfig 2006-08-09 18:14:42.000000000 +0200
@@ -416,7 +416,7 @@
config KPROBES
bool "Kprobes (EXPERIMENTAL)"
- depends on EXPERIMENTAL && MODULES
+ depends on KALLSYMS && EXPERIMENTAL && MODULES
help
Kprobes allows you to trap at almost any kernel address and
execute a callback function. register_kprobe() establishes
Index: linux-2.6/arch/x86_64/Kconfig
===================================================================
--- linux-2.6.orig/arch/x86_64/Kconfig 2006-08-08 17:13:13.000000000 +0200
+++ linux-2.6/arch/x86_64/Kconfig 2006-08-09 18:14:27.000000000 +0200
@@ -639,7 +639,7 @@
config KPROBES
bool "Kprobes (EXPERIMENTAL)"
- depends on EXPERIMENTAL && MODULES
+ depends on KALLSYMS && EXPERIMENTAL && MODULES
help
Kprobes allows you to trap at almost any kernel address and
execute a callback function. register_kprobe() establishes
-
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