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-rw-r--r--Documentation/admin-guide/kernel-parameters.txt38
-rw-r--r--include/linux/compiler-gcc.h2
-rw-r--r--include/linux/sprintf.h2
-rw-r--r--kernel/printk/internal.h2
-rw-r--r--kernel/printk/nbcon.c26
-rw-r--r--kernel/printk/printk.c20
-rw-r--r--lib/vsprintf.c70
-rw-r--r--mm/slub.c5
8 files changed, 129 insertions, 36 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 3f35d5b8c296..0dd5cd17e87e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1798,6 +1798,27 @@
backtraces on all cpus.
Format: 0 | 1
+ hash_pointers=
+ [KNL,EARLY]
+ By default, when pointers are printed to the console
+ or buffers via the %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. The choices are:
+ Format: { auto | always | never }
+ Default: auto
+
+ auto - Hash pointers unless slab_debug is enabled.
+ always - Always hash pointers (even if slab_debug is
+ enabled).
+ never - Never hash pointers. This option should only
+ be specified when debugging the kernel. Do
+ not use on production kernels. The boot
+ param "no_hash_pointers" is an alias for
+ this mode.
+
hashdist= [KNL,NUMA] Large hashes allocated during boot
are distributed across NUMA nodes. Defaults on
for 64-bit NUMA, off otherwise.
@@ -4120,18 +4141,7 @@
no_hash_pointers
[KNL,EARLY]
- 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. This option should only be specified when
- debugging the kernel. Please do not use on production
- kernels.
+ Alias for "hash_pointers=never".
nohibernate [HIBERNATION] Disable hibernation and resume.
@@ -6481,6 +6491,10 @@
Documentation/mm/slub.rst.
(slub_debug legacy name also accepted for now)
+ Using this option implies the "no_hash_pointers"
+ option which can be undone by adding the
+ "hash_pointers=always" option.
+
slab_max_order= [MM]
Determines the maximum allowed order for slabs.
A high setting may cause OOMs due to memory
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 32048052c64a..5d07c469b571 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -127,6 +127,8 @@
#define __diag_GCC_8(s)
#endif
+#define __diag_GCC_all(s) __diag(s)
+
#define __diag_ignore_all(option, comment) \
__diag(__diag_GCC_ignore option)
diff --git a/include/linux/sprintf.h b/include/linux/sprintf.h
index 51cab2def9ec..521bb2cd2648 100644
--- a/include/linux/sprintf.h
+++ b/include/linux/sprintf.h
@@ -22,7 +22,7 @@ __scanf(2, 0) int vsscanf(const char *, const char *, va_list);
/* These are for specific cases, do not use without real need */
extern bool no_hash_pointers;
-int no_hash_pointers_enable(char *str);
+void hash_pointers_finalize(bool slub_debug);
/* Used for Rust formatting ('%pA') */
char *rust_fmt_argument(char *buf, char *end, const void *ptr);
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 48a24e7b309d..567c9e100d47 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -64,6 +64,7 @@ struct dev_printk_info;
extern struct printk_ringbuffer *prb;
extern bool printk_kthreads_running;
+extern bool printk_kthreads_ready;
extern bool debug_non_panic_cpus;
__printf(4, 0)
@@ -180,6 +181,7 @@ static inline void nbcon_kthread_wake(struct console *con)
#define PRINTKRB_RECORD_MAX 0
#define printk_kthreads_running (false)
+#define printk_kthreads_ready (false)
/*
* In !PRINTK builds we still export console_sem
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index e7a3af81b173..646801813415 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -1690,6 +1690,9 @@ bool nbcon_alloc(struct console *con)
{
struct nbcon_state state = { };
+ /* Synchronize the kthread start. */
+ lockdep_assert_console_list_lock_held();
+
/* The write_thread() callback is mandatory. */
if (WARN_ON(!con->write_thread))
return false;
@@ -1720,12 +1723,15 @@ bool nbcon_alloc(struct console *con)
return false;
}
- if (printk_kthreads_running) {
+ if (printk_kthreads_ready && !have_boot_console) {
if (!nbcon_kthread_create(con)) {
kfree(con->pbufs);
con->pbufs = NULL;
return false;
}
+
+ /* Might be the first kthread. */
+ printk_kthreads_running = true;
}
}
@@ -1735,14 +1741,30 @@ bool nbcon_alloc(struct console *con)
/**
* nbcon_free - Free and cleanup the nbcon console specific data
* @con: Console to free/cleanup nbcon data
+ *
+ * Important: @have_nbcon_console must be updated before calling
+ * this function. In particular, it can be set only when there
+ * is still another nbcon console registered.
*/
void nbcon_free(struct console *con)
{
struct nbcon_state state = { };
- if (printk_kthreads_running)
+ /* Synchronize the kthread stop. */
+ lockdep_assert_console_list_lock_held();
+
+ if (printk_kthreads_running) {
nbcon_kthread_stop(con);
+ /* Might be the last nbcon console.
+ *
+ * Do not rely on printk_kthreads_check_locked(). It is not
+ * called in some code paths, see nbcon_free() callers.
+ */
+ if (!have_nbcon_console)
+ printk_kthreads_running = false;
+ }
+
nbcon_state_set(con, &state);
/* Boot consoles share global printk buffers. */
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 1eea80d0648e..0efbcdda9aab 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3574,7 +3574,7 @@ EXPORT_SYMBOL(console_resume);
static int unregister_console_locked(struct console *console);
/* True when system boot is far enough to create printer threads. */
-static bool printk_kthreads_ready __ro_after_init;
+bool printk_kthreads_ready __ro_after_init;
static struct task_struct *printk_legacy_kthread;
@@ -3713,6 +3713,7 @@ static void printk_kthreads_check_locked(void)
if (!printk_kthreads_ready)
return;
+ /* Start or stop the legacy kthread when needed. */
if (have_legacy_console || have_boot_console) {
if (!printk_legacy_kthread &&
force_legacy_kthread() &&
@@ -4204,14 +4205,6 @@ static int unregister_console_locked(struct console *console)
*/
synchronize_srcu(&console_srcu);
- if (console->flags & CON_NBCON)
- nbcon_free(console);
-
- console_sysfs_notify();
-
- if (console->exit)
- res = console->exit(console);
-
/*
* With this console gone, the global flags tracking registered
* console types may have changed. Update them.
@@ -4232,6 +4225,15 @@ static int unregister_console_locked(struct console *console)
if (!found_nbcon_con)
have_nbcon_console = found_nbcon_con;
+ /* @have_nbcon_console must be updated before calling nbcon_free(). */
+ if (console->flags & CON_NBCON)
+ nbcon_free(console);
+
+ console_sysfs_notify();
+
+ if (console->exit)
+ res = console->exit(console);
+
/* Changed console list, may require printer threads to start/stop. */
printk_kthreads_check_locked();
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 01699852f30c..02a811f6f661 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -60,6 +60,20 @@
bool no_hash_pointers __ro_after_init;
EXPORT_SYMBOL_GPL(no_hash_pointers);
+/*
+ * Hashed pointers policy selected by "hash_pointers=..." boot param
+ *
+ * `auto` - Hashed pointers enabled unless disabled by slub_debug_enabled=true
+ * `always` - Hashed pointers enabled unconditionally
+ * `never` - Hashed pointers disabled unconditionally
+ */
+enum hash_pointers_policy {
+ HASH_PTR_AUTO = 0,
+ HASH_PTR_ALWAYS,
+ HASH_PTR_NEVER
+};
+static enum hash_pointers_policy hash_pointers_mode __initdata;
+
noinline
static unsigned long long simple_strntoull(const char *startp, char **endp, unsigned int base, size_t max_chars)
{
@@ -1699,10 +1713,9 @@ char *escaped_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
return buf;
}
-#pragma GCC diagnostic push
-#ifndef __clang__
-#pragma GCC diagnostic ignored "-Wsuggest-attribute=format"
-#endif
+__diag_push();
+__diag_ignore(GCC, all, "-Wsuggest-attribute=format",
+ "Not a valid __printf() conversion candidate.");
static char *va_format(char *buf, char *end, struct va_format *va_fmt,
struct printf_spec spec)
{
@@ -1717,7 +1730,7 @@ static char *va_format(char *buf, char *end, struct va_format *va_fmt,
return buf;
}
-#pragma GCC diagnostic pop
+__diag_pop();
static noinline_for_stack
char *uuid_string(char *buf, char *end, const u8 *addr,
@@ -2271,12 +2284,23 @@ char *resource_or_range(const char *fmt, char *buf, char *end, void *ptr,
return resource_string(buf, end, ptr, spec, fmt);
}
-int __init no_hash_pointers_enable(char *str)
+void __init hash_pointers_finalize(bool slub_debug)
{
- if (no_hash_pointers)
- return 0;
+ switch (hash_pointers_mode) {
+ case HASH_PTR_ALWAYS:
+ no_hash_pointers = false;
+ break;
+ case HASH_PTR_NEVER:
+ no_hash_pointers = true;
+ break;
+ case HASH_PTR_AUTO:
+ default:
+ no_hash_pointers = slub_debug;
+ break;
+ }
- no_hash_pointers = true;
+ if (!no_hash_pointers)
+ return;
pr_warn("**********************************************************\n");
pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
@@ -2289,11 +2313,39 @@ int __init no_hash_pointers_enable(char *str)
pr_warn("** the kernel, report this immediately to your system **\n");
pr_warn("** administrator! **\n");
pr_warn("** **\n");
+ pr_warn("** Use hash_pointers=always to force this mode off **\n");
+ pr_warn("** **\n");
pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
pr_warn("**********************************************************\n");
+}
+
+static int __init hash_pointers_mode_parse(char *str)
+{
+ if (!str) {
+ pr_warn("Hash pointers mode empty; falling back to auto.\n");
+ hash_pointers_mode = HASH_PTR_AUTO;
+ } else if (strncmp(str, "auto", 4) == 0) {
+ pr_info("Hash pointers mode set to auto.\n");
+ hash_pointers_mode = HASH_PTR_AUTO;
+ } else if (strncmp(str, "never", 5) == 0) {
+ pr_info("Hash pointers mode set to never.\n");
+ hash_pointers_mode = HASH_PTR_NEVER;
+ } else if (strncmp(str, "always", 6) == 0) {
+ pr_info("Hash pointers mode set to always.\n");
+ hash_pointers_mode = HASH_PTR_ALWAYS;
+ } else {
+ pr_warn("Unknown hash_pointers mode '%s' specified; assuming auto.\n", str);
+ hash_pointers_mode = HASH_PTR_AUTO;
+ }
return 0;
}
+early_param("hash_pointers", hash_pointers_mode_parse);
+
+static int __init no_hash_pointers_enable(char *str)
+{
+ return hash_pointers_mode_parse("never");
+}
early_param("no_hash_pointers", no_hash_pointers_enable);
/*
diff --git a/mm/slub.c b/mm/slub.c
index b46f87662e71..f3d61b330a76 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -6314,9 +6314,8 @@ void __init kmem_cache_init(void)
if (debug_guardpage_minorder())
slub_max_order = 0;
- /* Print slub debugging pointers without hashing */
- if (__slub_debug_enabled())
- no_hash_pointers_enable(NULL);
+ /* Inform pointer hashing choice about slub debugging state. */
+ hash_pointers_finalize(__slub_debug_enabled());
kmem_cache_node = &boot_kmem_cache_node;
kmem_cache = &boot_kmem_cache;
generated by cgit v1.2.3 (git 2.0.4) at 2025-12-14 16:10:29 +0000