Merge branch 'for-4.16-deprecate-printk-pf' into for-4.16

Documentation/printk-formats.txt

@@ -50,42 +50,31 @@ Symbols/Function Pointers
 
 ::
 
+	%pS	versatile_init+0x0/0x110
+	%ps	versatile_init
 	%pF	versatile_init+0x0/0x110
 	%pf	versatile_init
-	%pS	versatile_init+0x0/0x110
 	%pSR	versatile_init+0x9/0x110
 		(with __builtin_extract_return_addr() translation)
-	%ps	versatile_init
 	%pB	prev_fn_of_versatile_init+0x88/0x88
 
-The ``F`` and ``f`` specifiers are for printing function pointers,
-for example, f->func, &gettimeofday. They have the same result as
-``S`` and ``s`` specifiers. But they do an extra conversion on
-ia64, ppc64 and parisc64 architectures where the function pointers
-are actually function descriptors.
+The ``S`` and ``s`` specifiers are used for printing a pointer in symbolic
+format. They result in the symbol name with (``S``) or without (``s``)
+offsets. If KALLSYMS are disabled then the symbol address is printed instead.
 
-The ``S`` and ``s`` specifiers can be used for printing symbols
-from direct addresses, for example, __builtin_return_address(0),
-(void *)regs->ip. They result in the symbol name with (``S``) or
-without (``s``) offsets. If KALLSYMS are disabled then the symbol
-address is printed instead.
+Note, that the ``F`` and ``f`` specifiers are identical to ``S`` (``s``)
+and thus deprecated. We have ``F`` and ``f`` because on ia64, ppc64 and
+parisc64 function pointers are indirect and, in fact, are function
+descriptors, which require additional dereferencing before we can lookup
+the symbol. As of now, ``S`` and ``s`` perform dereferencing on those
+platforms (when needed), so ``F`` and ``f`` exist for compatibility
+reasons only.
 
 The ``B`` specifier results in the symbol name with offsets and should be
 used when printing stack backtraces. The specifier takes into
 consideration the effect of compiler optimisations which may occur
 when tail-call``s are used and marked with the noreturn GCC attribute.
 
-Examples::
-
-	printk("Going to call: %pF\n", gettimeofday);
-	printk("Going to call: %pF\n", p->func);
-	printk("%s: called from %pS\n", __func__, (void *)_RET_IP_);
-	printk("%s: called from %pS\n", __func__,
-				(void *)__builtin_return_address(0));
-	printk("Faulted at %pS\n", (void *)regs->ip);
-	printk(" %s%pB\n", (reliable ? "" : "? "), (void *)*stack);
-
-
 Kernel Pointers
 ===============
 

arch/ia64/include/asm/sections.h

@@ -27,6 +27,8 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
 extern char __start_unwind[], __end_unwind[];
 extern char __start_ivt_text[], __end_ivt_text[];
 
+#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
+
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
@@ -38,6 +40,12 @@ static inline void *dereference_function_descriptor(void *ptr)
 	return ptr;
 }
 
+#undef dereference_kernel_function_descriptor
+static inline void *dereference_kernel_function_descriptor(void *ptr)
+{
+	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
+		return ptr;
+	return dereference_function_descriptor(ptr);
+}
 
 #endif /* _ASM_IA64_SECTIONS_H */
-

arch/ia64/kernel/module.c

@@ -36,6 +36,7 @@
 
 #include <asm/patch.h>
 #include <asm/unaligned.h>
+#include <asm/sections.h>
 
 #define ARCH_MODULE_DEBUG 0
 
@@ -918,3 +919,14 @@ module_arch_cleanup (struct module *mod)
 	if (mod->arch.core_unw_table)
 		unw_remove_unwind_table(mod->arch.core_unw_table);
 }
+
+void *dereference_module_function_descriptor(struct module *mod, void *ptr)
+{
+	Elf64_Shdr *opd = mod->arch.opd;
+
+	if (ptr < (void *)opd->sh_addr ||
+			ptr >= (void *)(opd->sh_addr + opd->sh_size))
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}

arch/ia64/kernel/vmlinux.lds.S

@@ -108,7 +108,9 @@ SECTIONS {
 	RODATA
 
 	.opd : AT(ADDR(.opd) - LOAD_OFFSET) {
+		__start_opd = .;
 		*(.opd)
+		__end_opd = .;
 	}
 
 	/*

arch/openrisc/kernel/traps.c

@@ -39,8 +39,7 @@
 #include <asm/io.h>
 #include <asm/pgtable.h>
 #include <asm/unwinder.h>
-
-extern char _etext, _stext;
+#include <asm/sections.h>
 
 int kstack_depth_to_print = 0x180;
 int lwa_flag;

arch/parisc/boot/compressed/vmlinux.lds.S

@@ -29,7 +29,9 @@ SECTIONS
 	. = ALIGN(16);
 	/* Linkage tables */
 	.opd : {
+		__start_opd = .;
 		*(.opd)
+		__end_opd = .;
 	} PROVIDE (__gp = .);
 	.plt : {
 		*(.plt)

arch/parisc/include/asm/sections.h

@@ -6,8 +6,14 @@
 #include <asm-generic/sections.h>
 
 #ifdef CONFIG_64BIT
+
+#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
+
 #undef dereference_function_descriptor
 void *dereference_function_descriptor(void *);
+
+#undef dereference_kernel_function_descriptor
+void *dereference_kernel_function_descriptor(void *);
 #endif
 
 #endif

arch/parisc/kernel/module.c

@@ -66,6 +66,7 @@
 
 #include <asm/pgtable.h>
 #include <asm/unwind.h>
+#include <asm/sections.h>
 
 #if 0
 #define DEBUGP printk
@@ -954,3 +955,18 @@ void module_arch_cleanup(struct module *mod)
 {
 	deregister_unwind_table(mod);
 }
+
+#ifdef CONFIG_64BIT
+void *dereference_module_function_descriptor(struct module *mod, void *ptr)
+{
+	unsigned long start_opd = (Elf64_Addr)mod->core_layout.base +
+				   mod->arch.fdesc_offset;
+	unsigned long end_opd = start_opd +
+				mod->arch.fdesc_count * sizeof(Elf64_Fdesc);
+
+	if (ptr < (void *)start_opd || ptr >= (void *)end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
+#endif

arch/parisc/kernel/process.c

@@ -276,6 +276,15 @@ void *dereference_function_descriptor(void *ptr)
 		ptr = p;
 	return ptr;
 }
+
+void *dereference_kernel_function_descriptor(void *ptr)
+{
+	if (ptr < (void *)__start_opd ||
+			ptr >= (void *)__end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
 #endif
 
 static inline unsigned long brk_rnd(void)

arch/parisc/kernel/vmlinux.lds.S

@@ -100,7 +100,9 @@ SECTIONS
 	. = ALIGN(16);
 	/* Linkage tables */
 	.opd : {
+		__start_opd = .;
 		*(.opd)
+		__end_opd = .;
 	} PROVIDE (__gp = .);
 	.plt : {
 		*(.plt)

arch/powerpc/include/asm/module.h

@@ -45,6 +45,9 @@ struct mod_arch_specific {
 	unsigned long tramp;
 #endif
 
+	/* For module function descriptor dereference */
+	unsigned long start_opd;
+	unsigned long end_opd;
 #else /* powerpc64 */
 	/* Indices of PLT sections within module. */
 	unsigned int core_plt_section;

arch/powerpc/include/asm/sections.h

@@ -66,6 +66,9 @@ static inline int overlaps_kvm_tmp(unsigned long start, unsigned long end)
 }
 
 #ifdef PPC64_ELF_ABI_v1
+
+#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
+
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
@@ -76,6 +79,15 @@ static inline void *dereference_function_descriptor(void *ptr)
 		ptr = p;
 	return ptr;
 }
+
+#undef dereference_kernel_function_descriptor
+static inline void *dereference_kernel_function_descriptor(void *ptr)
+{
+	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
 #endif /* PPC64_ELF_ABI_v1 */
 
 #endif

arch/powerpc/kernel/module_64.c

@@ -93,6 +93,15 @@ static unsigned int local_entry_offset(const Elf64_Sym *sym)
 {
 	return 0;
 }
+
+void *dereference_module_function_descriptor(struct module *mod, void *ptr)
+{
+	if (ptr < (void *)mod->arch.start_opd ||
+			ptr >= (void *)mod->arch.end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
 #endif
 
 #define STUB_MAGIC 0x73747562 /* stub */
@@ -344,6 +353,11 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr,
 		else if (strcmp(secstrings+sechdrs[i].sh_name,"__versions")==0)
 			dedotify_versions((void *)hdr + sechdrs[i].sh_offset,
 					  sechdrs[i].sh_size);
+		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".opd")) {
+			me->arch.start_opd = sechdrs[i].sh_addr;
+			me->arch.end_opd = sechdrs[i].sh_addr +
+					   sechdrs[i].sh_size;
+		}
 
 		/* We don't handle .init for the moment: rename to _init */
 		while ((p = strstr(secstrings + sechdrs[i].sh_name, ".init")))

arch/powerpc/kernel/vmlinux.lds.S

@@ -278,7 +278,9 @@ SECTIONS
 	}
 
 	.opd : AT(ADDR(.opd) - LOAD_OFFSET) {
+		__start_opd = .;
 		*(.opd)
+		__end_opd = .;
 	}
 
 	. = ALIGN(256);

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

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) + \
@@ -22,6 +26,56 @@
 
 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);

include/linux/module.h

@@ -606,6 +606,9 @@ 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. */
@@ -760,6 +763,13 @@ 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