diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c722ec19cd00485ceb9ba4dfce2cf9c5d2deb1d0..c549bc78910835b2c5cf862b703727e41d70381f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3281,6 +3281,21 @@
in certain environments such as networked servers or
real-time systems.
+ no_hash_pointers
+ Force pointers printed to the console or buffers to be
+ unhashed. By default, when a pointer is printed via %p
+ format string, that pointer is "hashed", i.e. obscured
+ by hashing the pointer value. This is a security feature
+ that hides actual kernel addresses from unprivileged
+ users, but it also makes debugging the kernel more
+ difficult since unequal pointers can no longer be
+ compared. However, if this command-line option is
+ specified, then all normal pointers will have their true
+ value printed. Pointers printed via %pK may still be
+ hashed. This option should only be specified when
+ debugging the kernel. Please do not use on production
+ kernels.
+
nohibernate [HIBERNATION] Disable hibernation and resume.
nohz= [KNL] Boottime enable/disable dynamic ticks
diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 4425a1dd4ef1c7d859730cfb30810853752852e5..0ea0e8258f14a5e5e5a1592154fa7bdd770eb4ce 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -16,8 +16,7 @@
#include "../tools/testing/selftests/kselftest_module.h"
-static unsigned total_tests __initdata;
-static unsigned failed_tests __initdata;
+KSTM_MODULE_GLOBALS();
static char pbl_buffer[PAGE_SIZE] __initdata;
diff --git a/lib/test_printf.c b/lib/test_printf.c
index 7ac87f18a10ff8209ad58278a79548a91e059795..a6755798e9e6204b98a61dde2af07bb044ca9844 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -30,11 +30,13 @@
#define PAD_SIZE 16
#define FILL_CHAR '$'
-static unsigned total_tests __initdata;
-static unsigned failed_tests __initdata;
+KSTM_MODULE_GLOBALS();
+
static char *test_buffer __initdata;
static char *alloced_buffer __initdata;
+extern bool no_hash_pointers;
+
static int __printf(4, 0) __init
do_test(int bufsize, const char *expect, int elen,
const char *fmt, va_list ap)
@@ -301,6 +303,12 @@ plain(void)
{
int err;
+ if (no_hash_pointers) {
+ pr_warn("skipping plain 'p' tests");
+ skipped_tests += 2;
+ return;
+ }
+
err = plain_hash();
if (err) {
pr_warn("plain 'p' does not appear to be hashed\n");
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3b53c73580c57756d2f8e78c36d8c93e07b92386..41ddc353ebb8220b2aa9e9071d4205bca9ed5187 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2090,6 +2090,32 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
return widen_string(buf, buf - buf_start, end, spec);
}
+/* Disable pointer hashing if requested */
+bool no_hash_pointers __ro_after_init;
+EXPORT_SYMBOL_GPL(no_hash_pointers);
+
+static int __init no_hash_pointers_enable(char *str)
+{
+ no_hash_pointers = true;
+
+ pr_warn("**********************************************************\n");
+ pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
+ pr_warn("** **\n");
+ pr_warn("** This system shows unhashed kernel memory addresses **\n");
+ pr_warn("** via the console, logs, and other interfaces. This **\n");
+ pr_warn("** might reduce the security of your system. **\n");
+ pr_warn("** **\n");
+ pr_warn("** If you see this message and you are not debugging **\n");
+ pr_warn("** the kernel, report this immediately to your system **\n");
+ pr_warn("** administrator! **\n");
+ pr_warn("** **\n");
+ pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
+ pr_warn("**********************************************************\n");
+
+ return 0;
+}
+early_param("no_hash_pointers", no_hash_pointers_enable);
+
/*
* Show a '%p' thing. A kernel extension is that the '%p' is followed
* by an extra set of alphanumeric characters that are extended format
@@ -2297,8 +2323,14 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
}
}
- /* default is to _not_ leak addresses, hash before printing */
- return ptr_to_id(buf, end, ptr, spec);
+ /*
+ * default is to _not_ leak addresses, so hash before printing,
+ * unless no_hash_pointers is specified on the command line.
+ */
+ if (unlikely(no_hash_pointers))
+ return pointer_string(buf, end, ptr, spec);
+ else
+ return ptr_to_id(buf, end, ptr, spec);
}
/*
diff --git a/tools/testing/selftests/kselftest_module.h b/tools/testing/selftests/kselftest_module.h
index e8eafaf0941aa716d9dc9a4b24dc0d3324101b6d..e2ea41de3f35446c65f13bf1f9938ade4c44c5ca 100644
--- a/tools/testing/selftests/kselftest_module.h
+++ b/tools/testing/selftests/kselftest_module.h
@@ -11,7 +11,8 @@
#define KSTM_MODULE_GLOBALS() \
static unsigned int total_tests __initdata; \
-static unsigned int failed_tests __initdata
+static unsigned int failed_tests __initdata; \
+static unsigned int skipped_tests __initdata
#define KSTM_CHECK_ZERO(x) do { \
total_tests++; \
@@ -21,11 +22,16 @@ static unsigned int failed_tests __initdata
} \
} while (0)
-static inline int kstm_report(unsigned int total_tests, unsigned int failed_tests)
+static inline int kstm_report(unsigned int total_tests, unsigned int failed_tests,
+ unsigned int skipped_tests)
{
- if (failed_tests == 0)
- pr_info("all %u tests passed\n", total_tests);
- else
+ if (failed_tests == 0) {
+ if (skipped_tests) {
+ pr_info("skipped %u tests\n", skipped_tests);
+ pr_info("remaining %u tests passed\n", total_tests);
+ } else
+ pr_info("all %u tests passed\n", total_tests);
+ } else
pr_warn("failed %u out of %u tests\n", failed_tests, total_tests);
return failed_tests ? -EINVAL : 0;
@@ -36,7 +42,7 @@ static int __init __module##_init(void) \
{ \
pr_info("loaded.\n"); \
selftest(); \
- return kstm_report(total_tests, failed_tests); \
+ return kstm_report(total_tests, failed_tests, skipped_tests); \
} \
static void __exit __module##_exit(void) \
{ \