[patch 143/166] samples/hw_breakpoint: drop use of kallsyms_lookup_name()

Andrew Morton
2020-04-07T03:11:42Z

From: Will Deacon <will@kernel.org>
Subject: samples/hw_breakpoint: drop use of kallsyms_lookup_name()

The 'data_breakpoint' test code is the only modular user of
kallsyms_lookup_name(), which was exported as part of fixing the test in
f60d24d2ad04 ("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.

Link: http://lkml.kernel.org/r/20200221114404.14641-3-will@kernel.org
Signed-off-by: Will Deacon <will@kernel.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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

samples/hw_breakpoint/data_breakpoint.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

--- a/samples/hw_breakpoint/data_breakpoint.c~samples-hw_breakpoint-drop-use-of-kallsyms_lookup_name
+++ a/samples/hw_breakpoint/data_breakpoint.c
@@ -23,7 +23,7 @@

struct perf_event * __percpu *sample_hbp;

-static char ksym_name[KSYM_NAME_LEN] = "pid_max";
+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");
@@ -41,9 +41,13 @@ static int __init hw_break_module_init(v
{
int ret;
struct perf_event_attr attr;
+ void *addr = __symbol_get(ksym_name);
+
+ if (!addr)
+ return -ENXIO;

hw_breakpoint_init(&attr);
- attr.bp_addr = kallsyms_lookup_name(ksym_name);
+ attr.bp_addr = (unsigned long)addr;
attr.bp_len = HW_BREAKPOINT_LEN_4;
attr.bp_type = HW_BREAKPOINT_W;

@@ -66,6 +70,7 @@ fail:
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);
}

_