Re: [PATCH 1/3] Kprobes: Make kprobe modules more portable (updated)
From: Ananth N Mavinakayanahalli
Date: Fri Aug 25 2006 - 03:05:14 EST
On Tue, Aug 22, 2006 at 10:54:48AM +0530, Ananth N Mavinakayanahalli wrote:
> From: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
>
> In an effort to make kprobe modules more portable, here is a patch that:
>
> o Introduces the "symbol_name" field to struct kprobe.
> The symbol->address resolution now happens in the kernel in an
> architecture agnostic manner. 64-bit powerpc users no longer have
> to specify the ".symbols"
> o Introduces the "offset" field to struct kprobe to allow a user to
> specify an offset into a symbol.
> o The legacy mechanism of specifying the kprobe.addr is still supported.
> However, if both the kprobe.addr and kprobe.symbol_name are specified,
> probe registration fails with an -EINVAL.
> o The symbol resolution code uses kallsyms_lookup_name(). So
> CONFIG_KPROBES now depends on CONFIG_KALLSYMS
> o Apparantly kprobe modules were the only legitimate out-of-tree user of
> the kallsyms_lookup_name() EXPORT. Now that the symbol resolution
> happens in-kernel, remove the EXPORT as suggested by Christoph Hellwig
> o Modify tcp_probe.c that uses the kprobe interface so as to make it
> work on multiple platforms (in its earlier form, the code wouldn't
> work, say, on powerpc)
Andrew,
Anil discovered that this patch has a case where, on powerpc, we potentially
end up dereferencing a NULL pointer. I have fixed that part and updated
the patch.
Please drop kprobes-make-kprobe-modules-more-portable.patch that is in
-mm currently. Please use this patch instead.
Thanks
Ananth
---
From: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
In an effort to make kprobe modules more portable, here is a patch that:
o Introduces the "symbol_name" field to struct kprobe.
The symbol->address resolution now happens in the kernel in an
architecture agnostic manner.
o Introduces the "offset" field to struct kprobe to allow a user to
specify an offset into a symbol.
o The legacy mechanism of specifying the kprobe.addr is still supported.
However, if both the kprobe.addr and kprobe.symbol_name are specified,
probe registration fails with an -EINVAL.
o The symbol resolution code uses kallsyms_lookup_name(). So
CONFIG_KPROBES now depends on CONFIG_KALLSYMS
o Apparantly kprobe modules were the only legitimate out-of-tree user of
the kallsyms_lookup_name() EXPORT. Now that the symbol resolution
happens in-kernel, remove the EXPORT as suggested by Christoph Hellwig
o Modify tcp_probe.c that uses the kprobe interface so as to make it
work on multiple platforms (in its earlier form, the code wouldn't
work, say, on powerpc)
Signed-off-by: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Signed-off-by: Prasanna S Panchamukhi <prasanna@xxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
---
arch/i386/Kconfig | 2 +-
arch/ia64/Kconfig | 2 +-
arch/powerpc/Kconfig | 2 +-
arch/sparc64/Kconfig | 2 +-
arch/x86_64/Kconfig | 2 +-
include/asm-powerpc/kprobes.h | 15 +++++++++++++++
include/linux/kprobes.h | 6 ++++++
kernel/kallsyms.c | 1 -
kernel/kprobes.c | 26 ++++++++++++++++++++++++++
net/ipv4/tcp_probe.c | 6 ++++--
10 files changed, 56 insertions(+), 8 deletions(-)
Index: linux-2.6.18-rc4/arch/i386/Kconfig
===================================================================
--- linux-2.6.18-rc4.orig/arch/i386/Kconfig
+++ linux-2.6.18-rc4/arch/i386/Kconfig
@@ -1129,7 +1129,7 @@ source "arch/i386/oprofile/Kconfig"
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-2.6.18-rc4/arch/ia64/Kconfig
===================================================================
--- linux-2.6.18-rc4.orig/arch/ia64/Kconfig
+++ linux-2.6.18-rc4/arch/ia64/Kconfig
@@ -510,7 +510,7 @@ source "arch/ia64/oprofile/Kconfig"
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-2.6.18-rc4/arch/powerpc/Kconfig
===================================================================
--- linux-2.6.18-rc4.orig/arch/powerpc/Kconfig
+++ linux-2.6.18-rc4/arch/powerpc/Kconfig
@@ -1045,7 +1045,7 @@ source "arch/powerpc/oprofile/Kconfig"
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-2.6.18-rc4/arch/sparc64/Kconfig
===================================================================
--- linux-2.6.18-rc4.orig/arch/sparc64/Kconfig
+++ linux-2.6.18-rc4/arch/sparc64/Kconfig
@@ -416,7 +416,7 @@ source "arch/sparc64/oprofile/Kconfig"
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-2.6.18-rc4/arch/x86_64/Kconfig
===================================================================
--- linux-2.6.18-rc4.orig/arch/x86_64/Kconfig
+++ linux-2.6.18-rc4/arch/x86_64/Kconfig
@@ -639,7 +639,7 @@ source "arch/x86_64/oprofile/Kconfig"
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-2.6.18-rc4/include/asm-powerpc/kprobes.h
===================================================================
--- linux-2.6.18-rc4.orig/include/asm-powerpc/kprobes.h
+++ linux-2.6.18-rc4/include/asm-powerpc/kprobes.h
@@ -44,6 +44,21 @@ typedef unsigned int kprobe_opcode_t;
#define IS_TDI(instr) (((instr) & 0xfc000000) == 0x08000000)
#define IS_TWI(instr) (((instr) & 0xfc000000) == 0x0c000000)
+/*
+ * 64bit powerpc uses function descriptors.
+ * Handle cases where:
+ * - User passes a <.symbol>
+ * - User passes a <symbol>
+ * - User passes a non-existant symbol, kallsyms_lookup_name
+ * returns 0. Don't deref the NULL pointer in that case
+ */
+#define kprobe_lookup_name(name, addr) \
+{ \
+ addr = (kprobe_opcode_t *)kallsyms_lookup_name(name); \
+ if (!(name[0] == '.') && addr) \
+ addr = *(kprobe_opcode_t **)addr; \
+}
+
#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-rc4/include/linux/kprobes.h
===================================================================
--- linux-2.6.18-rc4.orig/include/linux/kprobes.h
+++ linux-2.6.18-rc4/include/linux/kprobes.h
@@ -77,6 +77,12 @@ struct kprobe {
/* 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-2.6.18-rc4/kernel/kallsyms.c
===================================================================
--- linux-2.6.18-rc4.orig/kernel/kallsyms.c
+++ linux-2.6.18-rc4/kernel/kallsyms.c
@@ -154,7 +154,6 @@ unsigned long kallsyms_lookup_name(const
}
return module_kallsyms_lookup_name(name);
}
-EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
/*
* Lookup an address
Index: linux-2.6.18-rc4/kernel/kprobes.c
===================================================================
--- linux-2.6.18-rc4.orig/kernel/kprobes.c
+++ linux-2.6.18-rc4/kernel/kprobes.c
@@ -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, addr) \
+ addr = ((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 @@ static int __kprobes __register_kprobe(s
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;
+ kprobe_lookup_name(p->symbol_name, p->addr);
+ }
+
+ if (!p->addr)
+ return -EINVAL;
+ p->addr = (kprobe_opcode_t *)(((char *)p->addr)+ p->offset);
+
if ((!kernel_text_address((unsigned long) p->addr)) ||
in_kprobes_functions((unsigned long) p->addr))
return -EINVAL;
Index: linux-2.6.18-rc4/net/ipv4/tcp_probe.c
===================================================================
--- linux-2.6.18-rc4.orig/net/ipv4/tcp_probe.c
+++ linux-2.6.18-rc4/net/ipv4/tcp_probe.c
@@ -99,8 +99,10 @@ static int jtcp_sendmsg(struct kiocb *io
}
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),
};
-
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