Merge tag 'printk-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/printk...

Pull printk updates from Petr Mladek:

 - New "no_hash_pointers" kernel parameter causes that %p shows raw
   pointer values instead of hashed ones. It is intended only for
   debugging purposes. Misuse is prevented by a fat warning message that
   is inspired by trace_printk().

 - Prevent a possible deadlock when flushing printk_safe buffers during
   panic().

 - Fix performance regression caused by the lockless printk ringbuffer.
   It was visible with huge log buffer and long messages.

 - Documentation fix-up.

* tag 'printk-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  lib/vsprintf: no_hash_pointers prints all addresses as unhashed
  kselftest: add support for skipped tests
  lib: use KSTM_MODULE_GLOBALS macro in kselftest drivers
  printk: avoid prb_first_valid_seq() where possible
  printk: fix deadlock when kernel panic
  printk: rectify kernel-doc for prb_rec_init_wr()

[port kfence feature to rpi-5.10.95]
Signed-off-by: Sung-hun Kim <sfoon.kim@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Change-Id: I13558832bbd4970d2b35f39db052df735a6ced4f

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 4ee4dca..4320e97 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3288,6 +3288,21 @@
                        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/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h
index 5dc9d02..73cc80e 100644 (file)
--- a/kernel/printk/printk_ringbuffer.h
+++ b/kernel/printk/printk_ringbuffer.h
@@ -287,7 +287,7 @@ _DEFINE_PRINTKRB(name, descbits, avgtextbits, &_##name##_text[0])
 /* Writer Interface */
 
 /**
- * prb_rec_init_wd() - Initialize a buffer for writing records.
+ * prb_rec_init_wr() - Initialize a buffer for writing records.
  *
  * @r:             The record to initialize.
  * @text_buf_size: The needed text buffer size.

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 4425a1d..0ea0e82 100644 (file)
--- 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 7ac87f1..a675579 100644 (file)
--- 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 8ade1a8..ed2f709 100644 (file)
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2116,6 +2116,32 @@ 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
@@ -2323,8 +2349,14 @@ 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 e8eafaf..e2ea41d 100644 (file)
--- 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)               \
 {                                                      \