Messages in this thread Patch in this message | | | Date | Fri, 25 Aug 2006 12:35:18 +0530 | From | Ananth N Mavinakayanahalli <> | Subject | Re: [PATCH 1/3] Kprobes: Make kprobe modules more portable (updated) |
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On Tue, Aug 22, 2006 at 10:54:48AM +0530, Ananth N Mavinakayanahalli wrote: > From: Ananth N Mavinakayanahalli <ananth@in.ibm.com> > > 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@in.ibm.com>
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@in.ibm.com> Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
--- 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), }; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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