From b865ea64304ed591b7ab92d74efb12eff5ff4cbb Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Fri, 10 Nov 2017 08:48:25 +0900 Subject: sections: split dereference_function_descriptor() There are two format specifiers to print out a pointer in symbolic format: '%pS/%ps' and '%pF/%pf'. On most architectures, the two mean exactly the same thing, but some architectures (ia64, ppc64, parisc64) use an indirect pointer for C function pointers, where the function pointer points to a function descriptor (which in turn contains the actual pointer to the code). The '%pF/%pf, when used appropriately, automatically does the appropriate function descriptor dereference on such architectures. The "when used appropriately" part is tricky. Basically this is a subtle ABI detail, specific to some platforms, that made it to the API level and people can be unaware of it and miss the whole "we need to dereference the function" business out. [1] proves that point (note that it fixes only '%pF' and '%pS', there might be '%pf' and '%ps' cases as well). It appears that we can handle everything within the affected arches and make '%pS/%ps' smart enough to retire '%pF/%pf'. Function descriptors live in .opd elf section and all affected arches (ia64, ppc64, parisc64) handle it properly for kernel and modules. So we, technically, can decide if the dereference is needed by simply looking at the pointer: if it belongs to .opd section then we need to dereference it. The kernel and modules have their own .opd sections, obviously, that's why we need to split dereference_function_descriptor() and use separate kernel and module dereference arch callbacks. This patch does the first step, it a) adds dereference_kernel_function_descriptor() function. b) adds a weak alias to dereference_module_function_descriptor() function. So, for the time being, we will have: 1) dereference_function_descriptor() A generic function, that simply dereferences the pointer. There is bunch of places that call it: kgdbts, init/main.c, extable, etc. 2) dereference_kernel_function_descriptor() A function to call on kernel symbols that does kernel .opd section address range test. 3) dereference_module_function_descriptor() A function to call on modules' symbols that does modules' .opd section address range test. [1] https://marc.info/?l=linux-kernel&m=150472969730573 Link: http://lkml.kernel.org/r/20171109234830.5067-2-sergey.senozhatsky@gmail.com To: Fenghua Yu To: Benjamin Herrenschmidt To: Paul Mackerras To: Michael Ellerman To: James Bottomley Cc: Andrew Morton Cc: Jessica Yu Cc: Steven Rostedt Cc: linux-ia64@vger.kernel.org Cc: linux-parisc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky Tested-by: Tony Luck #ia64 Tested-by: Santosh Sivaraj #powerpc Tested-by: Helge Deller #parisc64 Signed-off-by: Petr Mladek --- include/linux/module.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/linux') diff --git a/include/linux/module.h b/include/linux/module.h index c69b49abe877..e6249795f9e2 100644 --- a/include/linux/module.h +++ b/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 -- cgit v1.2.3-59-g8ed1b From 04b8eb7a4ccd9ef9343e2720ccf2a5db8cfe2f67 Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Wed, 6 Dec 2017 13:36:49 +0900 Subject: symbol lookup: introduce dereference_symbol_descriptor() dereference_symbol_descriptor() invokes appropriate ARCH specific function descriptor dereference callbacks: - dereference_kernel_function_descriptor() if the pointer is a kernel symbol; - dereference_module_function_descriptor() if the pointer is a module symbol. This is the last step needed to make '%pS/%ps' smart enough to handle function descriptor dereference on affected ARCHs and to retire '%pF/%pf'. To refresh it: Some architectures (ia64, ppc64, parisc64) use an indirect pointer for C function pointers - the function pointer points to a function descriptor and we need to dereference it to get the actual function pointer. Function descriptors live in .opd elf section and all affected ARCHs (ia64, ppc64, parisc64) handle it properly for kernel and modules. So we, technically, can decide if the dereference is needed by simply looking at the pointer: if it belongs to .opd section then we need to dereference it. The kernel and modules have their own .opd sections, obviously, that's why we need to split dereference_function_descriptor() and use separate kernel and module dereference arch callbacks. Link: http://lkml.kernel.org/r/20171206043649.GB15885@jagdpanzerIV Cc: Fenghua Yu Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: James Bottomley Cc: Andrew Morton Cc: Jessica Yu Cc: Steven Rostedt Cc: linux-ia64@vger.kernel.org Cc: linux-parisc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky Tested-by: Tony Luck #ia64 Tested-by: Santosh Sivaraj #powerpc Tested-by: Helge Deller #parisc64 Signed-off-by: Petr Mladek --- Documentation/printk-formats.txt | 35 +++++++++----------------- include/linux/kallsyms.h | 54 ++++++++++++++++++++++++++++++++++++++++ kernel/kallsyms.c | 35 -------------------------- lib/vsprintf.c | 5 ++-- 4 files changed, 68 insertions(+), 61 deletions(-) (limited to 'include/linux') diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt index 361789df51ec..58c44cce90b6 100644 --- a/Documentation/printk-formats.txt +++ b/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 =============== diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h index 708f337d780b..e4f2e5a65f14 100644 --- a/include/linux/kallsyms.h +++ b/include/linux/kallsyms.h @@ -9,6 +9,10 @@ #include #include #include +#include +#include + +#include #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); diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 531ffa984bc2..0e4c0922908a 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -12,7 +12,6 @@ * compression (see scripts/kallsyms.c for a more complete description) */ #include -#include #include #include #include @@ -20,15 +19,12 @@ #include #include #include /* for cond_resched */ -#include #include #include #include #include #include -#include - /* * These will be re-linked against their real values * during the second link stage. @@ -52,37 +48,6 @@ extern const u16 kallsyms_token_index[] __weak; extern const unsigned long kallsyms_markers[] __weak; -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 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); -} - /* * Expand a compressed symbol data into the resulting uncompressed string, * if uncompressed string is too long (>= maxlen), it will be truncated, diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 1746bae94d41..16e2eefb0f79 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -40,7 +40,6 @@ #include "../mm/internal.h" /* For the trace_print_flags arrays */ #include /* for PAGE_SIZE */ -#include /* for dereference_function_descriptor() */ #include /* cpu_to_le16 */ #include @@ -1723,10 +1722,10 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, switch (*fmt) { case 'F': case 'f': - ptr = dereference_function_descriptor(ptr); - /* Fallthrough */ case 'S': case 's': + ptr = dereference_symbol_descriptor(ptr); + /* Fallthrough */ case 'B': return symbol_string(buf, end, ptr, spec, fmt); case 'R': -- cgit v1.2.3-59-g8ed1b From d2279c9d7f7db7f97567368bfc4539b3411adf8d Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Fri, 5 Jan 2018 19:25:38 +0900 Subject: kallsyms: remove print_symbol() function No more print_symbol()/__print_symbol() users left, remove these symbols. It was a very old API that encouraged people use continuous lines. It had been obsoleted by %pS format specifier in a normal printk() call. Link: http://lkml.kernel.org/r/20180105102538.GC471@jagdpanzerIV Cc: Andrew Morton Cc: Russell King Cc: Catalin Marinas Cc: Mark Salter Cc: Tony Luck Cc: David Howells Cc: Yoshinori Sato Cc: Guan Xuetao Cc: Borislav Petkov Cc: Greg Kroah-Hartman Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Vineet Gupta Cc: Fengguang Wu Cc: Steven Rostedt Cc: LKML Cc: linux-arm-kernel@lists.infradead.org Cc: linux-c6x-dev@linux-c6x.org Cc: linux-ia64@vger.kernel.org Cc: linux-am33-list@redhat.com Cc: linux-sh@vger.kernel.org Cc: linux-edac@vger.kernel.org Cc: x86@kernel.org Cc: linux-snps-arc@lists.infradead.org Cc: Sergey Senozhatsky Signed-off-by: Sergey Senozhatsky Suggested-by: Joe Perches [pmladek@suse.com: updated commit message] Signed-off-by: Petr Mladek --- Documentation/filesystems/sysfs.txt | 4 ++-- Documentation/translations/zh_CN/filesystems/sysfs.txt | 4 ++-- include/linux/kallsyms.h | 18 ------------------ kernel/kallsyms.c | 11 ----------- 4 files changed, 4 insertions(+), 33 deletions(-) (limited to 'include/linux') diff --git a/Documentation/filesystems/sysfs.txt b/Documentation/filesystems/sysfs.txt index 9a3658cc399e..a1426cabcef1 100644 --- a/Documentation/filesystems/sysfs.txt +++ b/Documentation/filesystems/sysfs.txt @@ -154,8 +154,8 @@ static ssize_t dev_attr_show(struct kobject *kobj, struct attribute *attr, if (dev_attr->show) ret = dev_attr->show(dev, dev_attr, buf); if (ret >= (ssize_t)PAGE_SIZE) { - print_symbol("dev_attr_show: %s returned bad count\n", - (unsigned long)dev_attr->show); + printk("dev_attr_show: %pS returned bad count\n", + dev_attr->show); } return ret; } diff --git a/Documentation/translations/zh_CN/filesystems/sysfs.txt b/Documentation/translations/zh_CN/filesystems/sysfs.txt index 7d3b05edb8ce..452271dda141 100644 --- a/Documentation/translations/zh_CN/filesystems/sysfs.txt +++ b/Documentation/translations/zh_CN/filesystems/sysfs.txt @@ -167,8 +167,8 @@ static ssize_t dev_attr_show(struct kobject *kobj, struct attribute *attr, if (dev_attr->show) ret = dev_attr->show(dev, dev_attr, buf); if (ret >= (ssize_t)PAGE_SIZE) { - print_symbol("dev_attr_show: %s returned bad count\n", - (unsigned long)dev_attr->show); + printk("dev_attr_show: %pS returned bad count\n", + dev_attr->show); } return ret; } diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h index 708f337d780b..c733941901b3 100644 --- a/include/linux/kallsyms.h +++ b/include/linux/kallsyms.h @@ -46,9 +46,6 @@ 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); @@ -118,23 +115,8 @@ 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/kernel/kallsyms.c b/kernel/kallsyms.c index 531ffa984bc2..32ba256f0092 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -464,17 +464,6 @@ int sprint_backtrace(char *buffer, unsigned long address) return __sprint_symbol(buffer, address, -1, 1); } -/* Look up a kernel symbol and print it to the kernel messages. */ -void __print_symbol(const char *fmt, unsigned long address) -{ - char buffer[KSYM_SYMBOL_LEN]; - - sprint_symbol(buffer, address); - - printk(fmt, buffer); -} -EXPORT_SYMBOL(__print_symbol); - /* To avoid using get_symbol_offset for every symbol, we carry prefix along. */ struct kallsym_iter { loff_t pos; -- cgit v1.2.3-59-g8ed1b