d8a84d33a4
The 'data_breakpoint' test code is the only modular user of
kallsyms_lookup_name(), which was exported as part of fixing the test in
f60d24d2ad ("hw-breakpoints: Fix broken hw-breakpoint sample module").
In preparation for un-exporting this symbol, switch the test over to using
__symbol_get(), which can be used to place breakpoints on exported
symbols.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Link: http://lkml.kernel.org/r/20200221114404.14641-3-will@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
83 lines
2.3 KiB
C
83 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/*
|
|
* data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address
|
|
*
|
|
* usage: insmod data_breakpoint.ko ksym=<ksym_name>
|
|
*
|
|
* 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 every time a write operation is performed on
|
|
* that variable.
|
|
*
|
|
* Copyright (C) IBM Corporation, 2009
|
|
*
|
|
* Author: K.Prasad <prasad@linux.vnet.ibm.com>
|
|
*/
|
|
#include <linux/module.h> /* Needed by all modules */
|
|
#include <linux/kernel.h> /* Needed for KERN_INFO */
|
|
#include <linux/init.h> /* Needed for the macros */
|
|
#include <linux/kallsyms.h>
|
|
|
|
#include <linux/perf_event.h>
|
|
#include <linux/hw_breakpoint.h>
|
|
|
|
struct perf_event * __percpu *sample_hbp;
|
|
|
|
static char ksym_name[KSYM_NAME_LEN] = "jiffies";
|
|
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 *bp,
|
|
struct perf_sample_data *data,
|
|
struct pt_regs *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;
|
|
struct perf_event_attr attr;
|
|
void *addr = __symbol_get(ksym_name);
|
|
|
|
if (!addr)
|
|
return -ENXIO;
|
|
|
|
hw_breakpoint_init(&attr);
|
|
attr.bp_addr = (unsigned long)addr;
|
|
attr.bp_len = HW_BREAKPOINT_LEN_4;
|
|
attr.bp_type = HW_BREAKPOINT_W;
|
|
|
|
sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler, NULL);
|
|
if (IS_ERR((void __force *)sample_hbp)) {
|
|
ret = PTR_ERR((void __force *)sample_hbp);
|
|
goto fail;
|
|
}
|
|
|
|
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_wide_hw_breakpoint(sample_hbp);
|
|
symbol_put(ksym_name);
|
|
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");
|