Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

Pull printk updates from Petr Mladek:

 - Add a console_msg_format command line option:

     The value "default" keeps the old "[time stamp] text\n" format. The
     value "syslog" allows to see the syslog-like "<log
     level>[timestamp] text" format.

     This feature was requested by people doing regression tests, for
     example, 0day robot. They want to have both filtered and full logs
     at hands.

 - Reduce the risk of softlockup:

     Pass the console owner in a busy loop.

     This is a new approach to the old problem. It was first proposed by
     Steven Rostedt on Kernel Summit 2017. It marks a context in which
     the console_lock owner calls console drivers and could not sleep.
     On the other side, printk() callers could detect this state and use
     a busy wait instead of a simple console_trylock(). Finally, the
     console_lock owner checks if there is a busy waiter at the end of
     the special context and eventually passes the console_lock to the
     waiter.

     The hand-off works surprisingly well and helps in many situations.
     Well, there is still a possibility of the softlockup, for example,
     when the flood of messages stops and the last owner still has too
     much to flush.

     There is increasing number of people having problems with
     printk-related softlockups. We might eventually need to get better
     solution. Anyway, this looks like a good start and promising
     direction.

 - Do not allow to schedule in console_unlock() called from printk():

     This reverts an older controversial commit. The reschedule helped
     to avoid softlockups. But it also slowed down the console output.
     This patch is obsoleted by the new console waiter logic described
     above. In fact, the reschedule made the hand-off less effective.

 - Deprecate "%pf" and "%pF" format specifier:

     It was needed on ia64, ppc64 and parisc64 to dereference function
     descriptors and show the real function address. It is done
     transparently by "%ps" and "pS" format specifier now.

     Sergey Senozhatsky found that all the function descriptors were in
     a special elf section and could be easily detected.

 - Remove printk_symbol() API:

     It has been obsoleted by "%pS" format specifier, and this change
     helped to remove few continuous lines and a less intuitive old API.

 - Remove redundant memsets:

     Sergey removed unnecessary memset when processing printk.devkmsg
     command line option.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: (27 commits)
  printk: drop redundant devkmsg_log_str memsets
  printk: Never set console_may_schedule in console_trylock()
  printk: Hide console waiter logic into helpers
  printk: Add console owner and waiter logic to load balance console writes
  kallsyms: remove print_symbol() function
  checkpatch: add pF/pf deprecation warning
  symbol lookup: introduce dereference_symbol_descriptor()
  parisc64: Add .opd based function descriptor dereference
  powerpc64: Add .opd based function descriptor dereference
  ia64: Add .opd based function descriptor dereference
  sections: split dereference_function_descriptor()
  openrisc: Fix conflicting types for _exext and _stext
  lib: do not use print_symbol()
  irq debug: do not use print_symbol()
  sysfs: do not use print_symbol()
  drivers: do not use print_symbol()
  x86: do not use print_symbol()
  unicore32: do not use print_symbol()
  sh: do not use print_symbol()
  mn10300: do not use print_symbol()
  ...

3 files changed, 70 insertions, 20 deletions

diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index 03cc5f9bba71..849cd8eb5ca0 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -30,6 +30,7 @@
  *	__ctors_start, __ctors_end
  *	__irqentry_text_start, __irqentry_text_end
  *	__softirqentry_text_start, __softirqentry_text_end
+ *	__start_opd, __end_opd
  */
 extern char _text[], _stext[], _etext[];
 extern char _data[], _sdata[], _edata[];
@@ -49,12 +50,15 @@ extern char __start_once[], __end_once[];
 /* Start and end of .ctors section - used for constructor calls. */
 extern char __ctors_start[], __ctors_end[];
 
+/* Start and end of .opd section - used for function descriptors. */
+extern char __start_opd[], __end_opd[];
+
 extern __visible const void __nosave_begin, __nosave_end;
 
-/* function descriptor handling (if any).  Override
- * in asm/sections.h */
+/* Function descriptor handling (if any).  Override in asm/sections.h */
 #ifndef dereference_function_descriptor
 #define dereference_function_descriptor(p) (p)
+#define dereference_kernel_function_descriptor(p) (p)
 #endif
 
 /* random extra sections (if any).  Override
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index bd118a6c60cb..d79d1e7486bd 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -9,6 +9,10 @@
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/stddef.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+
+#include <asm/sections.h>
 
 #define KSYM_NAME_LEN 128
 #define KSYM_SYMBOL_LEN (sizeof("%s+%#lx/%#lx [%s]") + (KSYM_NAME_LEN - 1) + \
@@ -16,6 +20,56 @@
 
 struct module;
 
+static inline int is_kernel_inittext(unsigned long addr)
+{
+	if (addr >= (unsigned long)_sinittext
+	    && addr <= (unsigned long)_einittext)
+		return 1;
+	return 0;
+}
+
+static inline int is_kernel_text(unsigned long addr)
+{
+	if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
+	    arch_is_kernel_text(addr))
+		return 1;
+	return in_gate_area_no_mm(addr);
+}
+
+static inline int is_kernel(unsigned long addr)
+{
+	if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
+		return 1;
+	return in_gate_area_no_mm(addr);
+}
+
+static inline int is_ksym_addr(unsigned long addr)
+{
+	if (IS_ENABLED(CONFIG_KALLSYMS_ALL))
+		return is_kernel(addr);
+
+	return is_kernel_text(addr) || is_kernel_inittext(addr);
+}
+
+static inline void *dereference_symbol_descriptor(void *ptr)
+{
+#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
+	struct module *mod;
+
+	ptr = dereference_kernel_function_descriptor(ptr);
+	if (is_ksym_addr((unsigned long)ptr))
+		return ptr;
+
+	preempt_disable();
+	mod = __module_address((unsigned long)ptr);
+	preempt_enable();
+
+	if (mod)
+		ptr = dereference_module_function_descriptor(mod, ptr);
+#endif
+	return ptr;
+}
+
 #ifdef CONFIG_KALLSYMS
 /* Lookup the address for a symbol. Returns 0 if not found. */
 unsigned long kallsyms_lookup_name(const char *name);
@@ -40,9 +94,6 @@ extern int sprint_symbol(char *buffer, unsigned long address);
 extern int sprint_symbol_no_offset(char *buffer, unsigned long address);
 extern int sprint_backtrace(char *buffer, unsigned long address);
 
-/* Look up a kernel symbol and print it to the kernel messages. */
-extern void __print_symbol(const char *fmt, unsigned long address);
-
 int lookup_symbol_name(unsigned long addr, char *symname);
 int lookup_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name);
 
@@ -112,23 +163,8 @@ static inline int kallsyms_show_value(void)
 	return false;
 }
 
-/* Stupid that this does nothing, but I didn't create this mess. */
-#define __print_symbol(fmt, addr)
 #endif /*CONFIG_KALLSYMS*/
 
-/* This macro allows us to keep printk typechecking */
-static __printf(1, 2)
-void __check_printsym_format(const char *fmt, ...)
-{
-}
-
-static inline void print_symbol(const char *fmt, unsigned long addr)
-{
-	__check_printsym_format(fmt, "");
-	__print_symbol(fmt, (unsigned long)
-		       __builtin_extract_return_addr((void *)addr));
-}
-
 static inline void print_ip_sym(unsigned long ip)
 {
 	printk("[<%p>] %pS\n", (void *) ip, (void *) ip);
diff --git a/include/linux/module.h b/include/linux/module.h
index 70245f1a3590..8dc7065d904d 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -612,6 +612,9 @@ int ref_module(struct module *a, struct module *b);
 	__mod ? __mod->name : "kernel";		\
 })
 
+/* Dereference module function descriptor */
+void *dereference_module_function_descriptor(struct module *mod, void *ptr);
+
 /* For kallsyms to ask for address resolution.  namebuf should be at
  * least KSYM_NAME_LEN long: a pointer to namebuf is returned if
  * found, otherwise NULL. */
@@ -766,6 +769,13 @@ static inline bool is_module_sig_enforced(void)
 	return false;
 }
 
+/* Dereference module function descriptor */
+static inline
+void *dereference_module_function_descriptor(struct module *mod, void *ptr)
+{
+	return ptr;
+}
+
 #endif /* CONFIG_MODULES */
 
 #ifdef CONFIG_SYSFS