From d8a84d33a4954b85c53faf77be48b5c2b559692e Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Mon, 6 Apr 2020 20:11:39 -0700 Subject: [PATCH] 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. Signed-off-by: Will Deacon Signed-off-by: Andrew Morton Reviewed-by: Christoph Hellwig Reviewed-by: Masami Hiramatsu Reviewed-by: Quentin Perret Cc: K.Prasad Cc: Thomas Gleixner Cc: Greg Kroah-Hartman Cc: Frederic Weisbecker Cc: Alexei Starovoitov Cc: Miroslav Benes Cc: Petr Mladek Cc: Joe Lawrence Link: http://lkml.kernel.org/r/20200221114404.14641-3-will@kernel.org Signed-off-by: Linus Torvalds --- samples/hw_breakpoint/data_breakpoint.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c index 469b36f93696..418c46fe5ffc 100644 --- a/samples/hw_breakpoint/data_breakpoint.c +++ b/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(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 = 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 @@ static int __init hw_break_module_init(void) 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); }