From 432039933a16b8227b7b267f46ac1c1b9b3adf14 Mon Sep 17 00:00:00 2001 From: "K.Prasad" Date: Mon, 1 Jun 2009 23:46:20 +0530 Subject: hw-breakpoints: sample HW breakpoint over kernel data address This patch introduces a sample kernel module to demonstrate the use of Hardware Breakpoint feature. It places a breakpoint over the kernel variable 'pid_max' to monitor all write operations and emits a function-backtrace when done. Signed-off-by: K.Prasad Signed-off-by: Frederic Weisbecker --- samples/Kconfig | 6 +++ samples/Makefile | 3 +- samples/hw_breakpoint/Makefile | 1 + samples/hw_breakpoint/data_breakpoint.c | 83 +++++++++++++++++++++++++++++++++ 4 files changed, 92 insertions(+), 1 deletion(-) create mode 100644 samples/hw_breakpoint/Makefile create mode 100644 samples/hw_breakpoint/data_breakpoint.c (limited to 'samples') diff --git a/samples/Kconfig b/samples/Kconfig index b75d28cba3f7..8458516c693c 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -45,5 +45,11 @@ config SAMPLE_KRETPROBES default m depends on SAMPLE_KPROBES && KRETPROBES +config SAMPLE_HW_BREAKPOINT + tristate "Build kernel hardware breakpoint examples -- loadable module only" + depends on HAVE_HW_BREAKPOINT && m + help + This builds kernel hardware breakpoint example modules. + endif # SAMPLES diff --git a/samples/Makefile b/samples/Makefile index 13e4b470b539..42e175598777 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -1,3 +1,4 @@ # Makefile for Linux samples code -obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/ tracepoints/ trace_events/ +obj-$(CONFIG_SAMPLES) += markers/ kobject/ kprobes/ tracepoints/ \ + trace_events/ hw_breakpoint/ diff --git a/samples/hw_breakpoint/Makefile b/samples/hw_breakpoint/Makefile new file mode 100644 index 000000000000..0f5c31c2fc47 --- /dev/null +++ b/samples/hw_breakpoint/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) += data_breakpoint.o diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c new file mode 100644 index 000000000000..9cbdbb871b7a --- /dev/null +++ b/samples/hw_breakpoint/data_breakpoint.c @@ -0,0 +1,83 @@ +/* + * data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * usage: insmod data_breakpoint.ko ksym= + * + * This file is a kernel module that places a breakpoint over ksym_name kernel + * variable using Hardware Breakpoint register. The corresponding handler which + * prints a backtrace is invoked everytime a write operation is performed on + * that variable. + * + * Copyright (C) IBM Corporation, 2009 + */ +#include /* Needed by all modules */ +#include /* Needed for KERN_INFO */ +#include /* Needed for the macros */ + +#include + +struct hw_breakpoint sample_hbp; + +static char ksym_name[KSYM_NAME_LEN] = "pid_max"; +module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO); +MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any" + " write operations on the kernel symbol"); + +void sample_hbp_handler(struct hw_breakpoint *temp, struct pt_regs + *temp_regs) +{ + printk(KERN_INFO "%s value is changed\n", ksym_name); + dump_stack(); + printk(KERN_INFO "Dump stack from sample_hbp_handler\n"); +} + +static int __init hw_break_module_init(void) +{ + int ret; + +#ifdef CONFIG_X86 + sample_hbp.info.name = ksym_name; + sample_hbp.info.type = HW_BREAKPOINT_WRITE; + sample_hbp.info.len = HW_BREAKPOINT_LEN_4; +#endif /* CONFIG_X86 */ + + sample_hbp.triggered = (void *)sample_hbp_handler; + + ret = register_kernel_hw_breakpoint(&sample_hbp); + + if (ret < 0) { + printk(KERN_INFO "Breakpoint registration failed\n"); + return ret; + } else + printk(KERN_INFO "HW Breakpoint for %s write installed\n", + ksym_name); + + return 0; +} + +static void __exit hw_break_module_exit(void) +{ + unregister_kernel_hw_breakpoint(&sample_hbp); + printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name); +} + +module_init(hw_break_module_init); +module_exit(hw_break_module_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("K.Prasad"); +MODULE_DESCRIPTION("ksym breakpoint"); -- cgit v1.2.3 From fa3012318bfb395552baef69bb1ebe87e64945c8 Mon Sep 17 00:00:00 2001 From: Michael Roth Date: Sun, 4 Oct 2009 18:14:29 +0200 Subject: Kconfig: Remove useless and sometimes wrong comments Additionally, some excessive newlines removed. Signed-off-by: Michael Roth Signed-off-by: Jiri Kosina --- samples/Kconfig | 3 --- 1 file changed, 3 deletions(-) (limited to 'samples') diff --git a/samples/Kconfig b/samples/Kconfig index b92bde3c6a89..04be681a3ded 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -1,5 +1,3 @@ -# samples/Kconfig - menuconfig SAMPLES bool "Sample kernel code" help @@ -41,4 +39,3 @@ config SAMPLE_KRETPROBES depends on SAMPLE_KPROBES && KRETPROBES endif # SAMPLES - -- cgit v1.2.3 From f60d24d2ad04977b0bd9e3eb35dba2d2fa569af9 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Tue, 10 Nov 2009 10:17:07 +0100 Subject: hw-breakpoints: Fix broken hw-breakpoint sample module The hw-breakpoint sample module has been broken during the hw-breakpoint internals refactoring. Propagate the changes to it. Reported-by: "K. Prasad" Signed-off-by: Frederic Weisbecker --- samples/hw_breakpoint/data_breakpoint.c | 43 ++++++++++++++++++--------------- 1 file changed, 24 insertions(+), 19 deletions(-) (limited to 'samples') diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c index 9cbdbb871b7a..5bc9819a819e 100644 --- a/samples/hw_breakpoint/data_breakpoint.c +++ b/samples/hw_breakpoint/data_breakpoint.c @@ -27,18 +27,19 @@ #include /* Needed by all modules */ #include /* Needed for KERN_INFO */ #include /* Needed for the macros */ +#include -#include +#include +#include -struct hw_breakpoint sample_hbp; +struct perf_event **sample_hbp; static char ksym_name[KSYM_NAME_LEN] = "pid_max"; module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO); MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any" " write operations on the kernel symbol"); -void sample_hbp_handler(struct hw_breakpoint *temp, struct pt_regs - *temp_regs) +static void sample_hbp_handler(struct perf_event *temp, void *data) { printk(KERN_INFO "%s value is changed\n", ksym_name); dump_stack(); @@ -48,30 +49,34 @@ void sample_hbp_handler(struct hw_breakpoint *temp, struct pt_regs static int __init hw_break_module_init(void) { int ret; + unsigned long addr; -#ifdef CONFIG_X86 - sample_hbp.info.name = ksym_name; - sample_hbp.info.type = HW_BREAKPOINT_WRITE; - sample_hbp.info.len = HW_BREAKPOINT_LEN_4; -#endif /* CONFIG_X86 */ + addr = kallsyms_lookup_name(ksym_name); - sample_hbp.triggered = (void *)sample_hbp_handler; + sample_hbp = register_wide_hw_breakpoint(addr, HW_BREAKPOINT_LEN_4, + HW_BREAKPOINT_W | HW_BREAKPOINT_R, + sample_hbp_handler, true); + if (IS_ERR(sample_hbp)) { + ret = PTR_ERR(sample_hbp); + goto fail; + } else if (!sample_hbp) { + ret = -EINVAL; + goto fail; + } - ret = register_kernel_hw_breakpoint(&sample_hbp); - - if (ret < 0) { - printk(KERN_INFO "Breakpoint registration failed\n"); - return ret; - } else - printk(KERN_INFO "HW Breakpoint for %s write installed\n", - ksym_name); + printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name); return 0; + +fail: + printk(KERN_INFO "Breakpoint registration failed\n"); + + return ret; } static void __exit hw_break_module_exit(void) { - unregister_kernel_hw_breakpoint(&sample_hbp); + unregister_wide_hw_breakpoint(sample_hbp); printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name); } -- cgit v1.2.3 From ba6909b719a5ccc0c8100d2895bb7ff557b2eeae Mon Sep 17 00:00:00 2001 From: "K.Prasad" Date: Mon, 23 Nov 2009 21:17:13 +0530 Subject: hw-breakpoint: Attribute authorship of hw-breakpoint related files Attribute authorship to developers of hw-breakpoint related files. Signed-off-by: K.Prasad Cc: Alan Stern Cc: Frederic Weisbecker LKML-Reference: <20091123154713.GA5593@in.ibm.com> [ v2: moved it to latest -tip ] Signed-off-by: Ingo Molnar --- samples/hw_breakpoint/data_breakpoint.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'samples') diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c index 5bc9819a819e..95063818bcf4 100644 --- a/samples/hw_breakpoint/data_breakpoint.c +++ b/samples/hw_breakpoint/data_breakpoint.c @@ -23,6 +23,8 @@ * that variable. * * Copyright (C) IBM Corporation, 2009 + * + * Author: K.Prasad */ #include /* Needed by all modules */ #include /* Needed for KERN_INFO */ -- cgit v1.2.3 From 605bfaee9078cd0b01d83402315389839ee4bb5c Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 26 Nov 2009 05:35:42 +0100 Subject: hw-breakpoints: Simplify error handling in breakpoint creation requests This simplifies the error handling when we create a breakpoint. We don't need to check the NULL return value corner case anymore since we have improved perf_event_create_kernel_counter() to always return an error code in the failure case. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Paul Mackerras Cc: Steven Rostedt Cc: Prasad LKML-Reference: <1259210142-5714-3-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar --- samples/hw_breakpoint/data_breakpoint.c | 3 --- 1 file changed, 3 deletions(-) (limited to 'samples') diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c index 95063818bcf4..ee7f9fbaffbd 100644 --- a/samples/hw_breakpoint/data_breakpoint.c +++ b/samples/hw_breakpoint/data_breakpoint.c @@ -61,9 +61,6 @@ static int __init hw_break_module_init(void) if (IS_ERR(sample_hbp)) { ret = PTR_ERR(sample_hbp); goto fail; - } else if (!sample_hbp) { - ret = -EINVAL; - goto fail; } printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name); -- cgit v1.2.3 From dd1853c3f493f6d22d9e5390b192a07b73d2ac0a Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Fri, 27 Nov 2009 04:55:54 +0100 Subject: hw-breakpoints: Use struct perf_event_attr to define kernel breakpoints Kernel breakpoints are created using functions in which we pass breakpoint parameters as individual variables: address, length and type. Although it fits well for x86, this just does not scale across architectures that may support this api later as these may have more or different needs. Pass in a perf_event_attr structure instead because it is meant to evolve as much as possible into a generic hardware breakpoint parameter structure. Reported-by: K.Prasad Signed-off-by: Frederic Weisbecker LKML-Reference: <1259294154-5197-2-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar --- samples/hw_breakpoint/data_breakpoint.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'samples') diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c index ee7f9fbaffbd..29525500df00 100644 --- a/samples/hw_breakpoint/data_breakpoint.c +++ b/samples/hw_breakpoint/data_breakpoint.c @@ -51,13 +51,13 @@ static void sample_hbp_handler(struct perf_event *temp, void *data) static int __init hw_break_module_init(void) { int ret; - unsigned long addr; + DEFINE_BREAKPOINT_ATTR(attr); - addr = kallsyms_lookup_name(ksym_name); + attr.bp_addr = kallsyms_lookup_name(ksym_name); + attr.bp_len = HW_BREAKPOINT_LEN_4; + attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R; - sample_hbp = register_wide_hw_breakpoint(addr, HW_BREAKPOINT_LEN_4, - HW_BREAKPOINT_W | HW_BREAKPOINT_R, - sample_hbp_handler, true); + sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler); if (IS_ERR(sample_hbp)) { ret = PTR_ERR(sample_hbp); goto fail; -- cgit v1.2.3 From b326e9560a28fc3e950637ef51847ed8f05c1335 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 5 Dec 2009 09:44:31 +0100 Subject: hw-breakpoints: Use overflow handler instead of the event callback struct perf_event::event callback was called when a breakpoint triggers. But this is a rather opaque callback, pretty tied-only to the breakpoint API and not really integrated into perf as it triggers even when we don't overflow. We prefer to use overflow_handler() as it fits into the perf events rules, being called only when we overflow. Reported-by: Peter Zijlstra Signed-off-by: Frederic Weisbecker Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: "K. Prasad" --- samples/hw_breakpoint/data_breakpoint.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'samples') diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c index 29525500df00..c69cbe9b2426 100644 --- a/samples/hw_breakpoint/data_breakpoint.c +++ b/samples/hw_breakpoint/data_breakpoint.c @@ -41,7 +41,9 @@ module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO); MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any" " write operations on the kernel symbol"); -static void sample_hbp_handler(struct perf_event *temp, void *data) +static void sample_hbp_handler(struct perf_event *bp, int nmi, + struct perf_sample_data *data, + struct pt_regs *regs) { printk(KERN_INFO "%s value is changed\n", ksym_name); dump_stack(); @@ -51,8 +53,9 @@ static void sample_hbp_handler(struct perf_event *temp, void *data) static int __init hw_break_module_init(void) { int ret; - DEFINE_BREAKPOINT_ATTR(attr); + struct perf_event_attr attr; + hw_breakpoint_init(&attr); attr.bp_addr = kallsyms_lookup_name(ksym_name); attr.bp_len = HW_BREAKPOINT_LEN_4; attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R; -- cgit v1.2.3