Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750880AbWHGMDY (ORCPT ); Mon, 7 Aug 2006 08:03:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750881AbWHGMDY (ORCPT ); Mon, 7 Aug 2006 08:03:24 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:654 "EHLO e36.co.us.ibm.com") by vger.kernel.org with ESMTP id S1750865AbWHGMDX (ORCPT ); Mon, 7 Aug 2006 08:03:23 -0400 Date: Mon, 7 Aug 2006 17:34:47 +0530 From: Ananth N Mavinakayanahalli To: linux-kernel@vger.kernel.org Cc: Prasanna S Panchamukhi , Anil S Keshavamurthy , Jim Keniston Subject: [PATCH 3/3] Kprobes: Update Documentation/kprobes.txt Message-ID: <20060807120447.GE15253@in.ibm.com> Reply-To: ananth@in.ibm.com References: <20060807115537.GA15253@in.ibm.com> <20060807120024.GD15253@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060807120024.GD15253@in.ibm.com> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6995 Lines: 227 From: Ananth N Mavinakayanahalli Update Documentation/kprobes.txt to reflect addition of KPROBE_ADDR, KPROBE_RETVAL and the in-kernel symbol resolution. While at it: - Document usage of JPROBE_RETURN - Update the references list - Update module examples to use module_init/module_exit interfaces --- Signed-off-by: Ananth N Mavinakayanahalli Acked-by: Jim Keniston --- Documentation/kprobes.txt | 77 ++++++++++++++++++++++++++++------------------ 1 files changed, 47 insertions(+), 30 deletions(-) Index: linux-2.6.18-rc3/Documentation/kprobes.txt =================================================================== --- linux-2.6.18-rc3.orig/Documentation/kprobes.txt +++ linux-2.6.18-rc3/Documentation/kprobes.txt @@ -179,6 +179,21 @@ occurs during execution of kp->pre_handl or during single-stepping of the probed instruction, Kprobes calls kp->fault_handler. Any or all handlers can be NULL. +NOTE: +1. The KPROBE_ADDR macro is provided as an aid to make kprobe modules +portable. Some architectures (notably powerpc) uses function descriptors +due to which a kallsyms_lookup_name("probepoint") will give a data address, +which, incidentally, is a placeholder for the actual text address. It is +therefore advised to use: + + kp.addr = KPROBE_ADDR("probepoint"); + +2. With the introduction of the "symbol_name" field to struct kprobe, +the probepoint address resolution will now be taken care of by the kernel. +The following will also work: + + kp.symbol_name = "symbol_name"; + register_kprobe() returns 0 on success, or a negative errno otherwise. User's pre-handler (kp->pre_handler): @@ -225,6 +240,12 @@ control to Kprobes.) If the probed func fastcall, or anything else that affects how args are passed, the handler's declaration must match. +NOTE: Similar to KPROBE_ADDR, a macro JPROBE_ENTRY is provided to handle +architecture-specific aliasing of jp->entry. In the interest of +portability, it is advised to use: + + jp->entry = JPROBE_ENTRY(handler); + register_jprobe() returns 0 on success, or a negative errno otherwise. 4.3 register_kretprobe @@ -251,6 +272,11 @@ of interest: - ret_addr: the return address - rp: points to the corresponding kretprobe object - task: points to the corresponding task struct + +The KPROBE_RETVAL(regs) macro provides a simple abstraction to extract +the return value from the appropriate register as defined by the +architecture's ABI. + The handler's return value is currently ignored. 4.4 unregister_*probe @@ -369,7 +395,6 @@ stack trace and selected i386 registers #include #include #include -#include #include /*For each probe you need to allocate a kprobe structure*/ @@ -403,18 +428,14 @@ int handler_fault(struct kprobe *p, stru return 0; } -int init_module(void) +static int __init kprobe_init(void) { int ret; kp.pre_handler = handler_pre; kp.post_handler = handler_post; kp.fault_handler = handler_fault; - kp.addr = (kprobe_opcode_t*) kallsyms_lookup_name("do_fork"); - /* register the kprobe now */ - if (!kp.addr) { - printk("Couldn't find %s to plant kprobe\n", "do_fork"); - return -1; - } + kp.symbol_name = "do_fork"; + if ((ret = register_kprobe(&kp) < 0)) { printk("register_kprobe failed, returned %d\n", ret); return -1; @@ -423,12 +444,14 @@ int init_module(void) return 0; } -void cleanup_module(void) +static void __exit kprobe_exit(void) { unregister_kprobe(&kp); printk("kprobe unregistered\n"); } +module_init(kprobe_init) +module_exit(kprobe_exit) MODULE_LICENSE("GPL"); ----- cut here ----- @@ -463,7 +486,6 @@ the arguments of do_fork(). #include #include #include -#include /* * Jumper probe for do_fork. @@ -485,17 +507,13 @@ long jdo_fork(unsigned long clone_flags, } static struct jprobe my_jprobe = { - .entry = (kprobe_opcode_t *) jdo_fork + .entry = JPROBE_ENTRY(jdo_fork) }; -int init_module(void) +static int __init jprobe_init(void) { int ret; - my_jprobe.kp.addr = (kprobe_opcode_t *) kallsyms_lookup_name("do_fork"); - if (!my_jprobe.kp.addr) { - printk("Couldn't find %s to plant jprobe\n", "do_fork"); - return -1; - } + my_jprobe.kp.symbol_name = "do_fork"; if ((ret = register_jprobe(&my_jprobe)) <0) { printk("register_jprobe failed, returned %d\n", ret); @@ -506,12 +524,14 @@ int init_module(void) return 0; } -void cleanup_module(void) +static void __exit jprobe_exit(void) { unregister_jprobe(&my_jprobe); printk("jprobe unregistered\n"); } +module_init(jprobe_init) +module_exit(jprobe_exit) MODULE_LICENSE("GPL"); ----- cut here ----- @@ -530,16 +550,13 @@ report failed calls to sys_open(). #include #include #include -#include static const char *probed_func = "sys_open"; /* Return-probe handler: If the probed function fails, log the return value. */ static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs) { - // Substitute the appropriate register name for your architecture -- - // e.g., regs->rax for x86_64, regs->gpr[3] for ppc64. - int retval = (int) regs->eax; + int retval = KPROBE_RETVAL(regs); if (retval < 0) { printk("%s returns %d\n", probed_func, retval); } @@ -552,15 +569,11 @@ static struct kretprobe my_kretprobe = { .maxactive = 20 }; -int init_module(void) +static int __init kretprobe_init(void) { int ret; - my_kretprobe.kp.addr = - (kprobe_opcode_t *) kallsyms_lookup_name(probed_func); - if (!my_kretprobe.kp.addr) { - printk("Couldn't find %s to plant return probe\n", probed_func); - return -1; - } + my_kretprobe.kp.symbol_name = (char *)probed_func; + if ((ret = register_kretprobe(&my_kretprobe)) < 0) { printk("register_kretprobe failed, returned %d\n", ret); return -1; @@ -569,7 +582,7 @@ int init_module(void) return 0; } -void cleanup_module(void) +static void __exit kretprobe_exit(void) { unregister_kretprobe(&my_kretprobe); printk("kretprobe unregistered\n"); @@ -578,6 +591,8 @@ void cleanup_module(void) my_kretprobe.nmissed, probed_func); } +module_init(kretprobe_init) +module_exit(kretprobe_exit) MODULE_LICENSE("GPL"); ----- cut here ----- @@ -590,3 +605,5 @@ messages.) For additional information on Kprobes, refer to the following URLs: http://www-106.ibm.com/developerworks/library/l-kprobes.html?ca=dgr-lnxw42Kprobe http://www.redhat.com/magazine/005mar05/features/kprobes/ +http://www-users.cs.umn.edu/~boutcher/kprobes/ +http://www.linuxsymposium.org/2006/linuxsymposium_procv2.pdf (pages 101-115) - 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/