/* ksym_mod.c - functions for building symbol lookup tables for klogd Copyright (c) 1995, 1996 Dr. G.W. Wettstein Copyright (c) 1996 Enjellic Systems Development This file is part of the sysklogd package, a kernel and system log daemon. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ /* * This file implements functions which are useful for building * a symbol lookup table based on the in kernel symbol table * maintained by the Linux kernel. * * Proper logging of kernel panics generated by loadable modules * tends to be difficult. Since the modules are loaded dynamically * their addresses are not known at kernel load time. A general * protection fault (Oops) cannot be properly deciphered with * classic methods using the static symbol map produced at link time. * * One solution to this problem is to have klogd attempt to translate * addresses from module when the fault occurs. By referencing the * the kernel symbol table proper resolution of these symbols is made * possible. * * At least that is the plan. * * Wed Aug 21 09:20:09 CDT 1996: Dr. Wettstein * The situation where no module support has been compiled into a * kernel is now detected. An informative message is output indicating * that the kernel has no loadable module support whenever kernel * module symbols are loaded. * * An informative message is printed indicating the number of kernel * modules and the number of symbols loaded from these modules. * * Sun Jun 15 16:23:29 MET DST 1997: Michael Alan Dorman * Some more glibc patches made by . * * Sat Jan 10 15:00:18 CET 1998: Martin Schulze * Fixed problem with klogd not being able to be built on a kernel * newer than 2.1.18. It was caused by modified structures * inside the kernel that were included. I have worked in a * patch from Alessandro Suardi . * * Sun Jan 25 20:57:34 CET 1998: Martin Schulze * Another patch for Linux/alpha by Christopher C Chimelis * . * * Thu Mar 19 23:39:29 CET 1998: Manuel Rodrigues * Changed lseek() to llseek() in order to support > 2GB address * space which provided by kernels > 2.1.70. * * Mon Apr 13 18:18:45 CEST 1998: Martin Schulze * Removed as it's no longer part of recent glibc * versions. Added prototyp for llseek() which has been * forgotton in from glibc. Added more log * information if problems occurred while reading a system map * file, by submission from Mark Simon Phillips . * * Sun Jan 3 18:38:03 CET 1999: Martin Schulze * Corrected return value of AddModule if /dev/kmem can't be * loaded. This will prevent klogd from segfaulting if /dev/kmem * is not available. Patch from Topi Miettinen . * * Tue Sep 12 23:11:13 CEST 2000: Martin Schulze * Changed llseek() to lseek64() in order to skip a libc warning. */ /* Includes. */ #include #include #include #include #include #include #include #if !defined(__GLIBC__) #include #include #include #else /* __GLIBC__ */ #include #include extern __off64_t lseek64 __P ((int __fd, __off64_t __offset, int __whence)); extern int get_kernel_syms __P ((struct kernel_sym *__table)); #endif /* __GLIBC__ */ #include #include #include #include "klogd.h" #include "ksyms.h" #if !defined(__GLIBC__) /* * The following bit uses some kernel/library magic to product what * looks like a function call to user level code. This function is * actually a system call in disguise. The purpose of the getsyms * call is to return a current copy of the in-kernel symbol table. */ #define __LIBRARY__ #include #define __NR_getsyms __NR_get_kernel_syms _syscall1(int, getsyms, struct kernel_sym *, syms); #undef __LIBRARY__ extern int getsyms(struct kernel_sym *); #else /* __GLIBC__ */ #define getsyms get_kernel_syms #endif /* __GLIBC__ */ /* Variables static to this module. */ struct sym_table { unsigned long value; char *name; }; struct Module { struct sym_table *sym_array; int num_syms; char *name; struct module module; #if LINUX_VERSION_CODE >= 0x20112 struct module_info module_info; #endif }; static int num_modules = 0; struct Module *sym_array_modules = (struct Module *) 0; static int have_modules = 0; #if defined(TEST) static int debugging = 1; #else extern int debugging; #endif /* Function prototypes. */ static void FreeModules(void); static int AddSymbol(struct Module *mp, unsigned long, char *); static int AddModule(unsigned long, char *); static int symsort(const void *, const void *); /************************************************************************** * Function: InitMsyms * * Purpose: This function is responsible for building a symbol * table which can be used to resolve addresses for * loadable modules. * * Arguements: Void * * Return: A boolean return value is assumed. * * A false value indicates that something went wrong. * * True if loading is successful. **************************************************************************/ extern int InitMsyms() { auto int rtn, tmp; auto struct kernel_sym *ksym_table, *p; /* Initialize the kernel module symbol table. */ FreeModules(); /* * The system call which returns the kernel symbol table has * essentialy two modes of operation. Called with a null pointer * the system call returns the number of symbols defined in the * the table. * * The second mode of operation is to pass a valid pointer to * the call which will then load the current symbol table into * the memory provided. * * Returning the symbol table is essentially an all or nothing * proposition so we need to pre-allocate enough memory for the * complete table regardless of how many symbols we need. * * Bummer. */ if ( (rtn = getsyms((struct kernel_sym *) 0)) < 0 ) { if ( errno == ENOSYS ) Syslog(LOG_INFO, "No module symbols loaded - " "kernel modules not enabled.\n"); else Syslog(LOG_ERR, "Error loading kernel symbols " \ "- %s\n", strerror(errno)); return(0); } if ( debugging ) fprintf(stderr, "Loading kernel module symbols - " "Size of table: %d\n", rtn); ksym_table = (struct kernel_sym *) malloc(rtn * \ sizeof(struct kernel_sym)); if ( ksym_table == (struct kernel_sym *) 0 ) { Syslog(LOG_WARNING, " Failed memory allocation for kernel " \ "symbol table.\n"); return(0); } if ( (rtn = getsyms(ksym_table)) < 0 ) { Syslog(LOG_WARNING, "Error reading kernel symbols - %s\n", \ strerror(errno)); return(0); } /* * Build a symbol table compatible with the other one used by * klogd. */ tmp = rtn; p = ksym_table; while ( tmp-- ) { if ( !AddModule(p->value, p->name) ) { Syslog(LOG_WARNING, "Error adding kernel module table " "entry.\n"); free(ksym_table); return(0); } ++p; } /* Sort the symbol tables in each module. */ for (rtn = tmp= 0; tmp < num_modules; ++tmp) { rtn += sym_array_modules[tmp].num_syms; if ( sym_array_modules[tmp].num_syms < 2 ) continue; qsort(sym_array_modules[tmp].sym_array, \ sym_array_modules[tmp].num_syms, \ sizeof(struct sym_table), symsort); } if ( rtn == 0 ) Syslog(LOG_INFO, "No module symbols loaded."); else Syslog(LOG_INFO, "Loaded %d %s from %d module%s", rtn, \ (rtn == 1) ? "symbol" : "symbols", \ num_modules, (num_modules == 1) ? "." : "s."); free(ksym_table); return(1); } static int symsort(p1, p2) const void *p1; const void *p2; { auto const struct sym_table *sym1 = p1, *sym2 = p2; if ( sym1->value < sym2->value ) return(-1); if ( sym1->value == sym2->value ) return(0); return(1); } /************************************************************************** * Function: FreeModules * * Purpose: This function is used to free all memory which has been * allocated for the modules and their symbols. * * Arguements: None specified. * * Return: void **************************************************************************/ static void FreeModules() { auto int nmods, nsyms; auto struct Module *mp; /* Check to see if the module symbol tables need to be cleared. */ have_modules = 0; if ( num_modules == 0 ) return; for (nmods= 0; nmods < num_modules; ++nmods) { mp = &sym_array_modules[nmods]; if ( mp->num_syms == 0 ) continue; for (nsyms= 0; nsyms < mp->num_syms; ++nsyms) free(mp->sym_array[nsyms].name); free(mp->sym_array); } free(sym_array_modules); sym_array_modules = (struct Module *) 0; num_modules = 0; return; } /************************************************************************** * Function: AddModule * * Purpose: This function is responsible for adding a module to * the list of currently loaded modules. * * Arguements: (unsigned long) address, (char *) symbol * * address:-> The address of the module. * * symbol:-> The name of the module. * * Return: int **************************************************************************/ static int AddModule(address, symbol) unsigned long address; char *symbol; { auto int memfd; auto struct Module *mp; /* Return if we have loaded the modules. */ if ( have_modules ) return(1); /* * The following section of code is responsible for determining * whether or not we are done reading the list of modules. */ if ( symbol[0] == '#' ) { if ( symbol[1] == '\0' ) { /* * A symbol which consists of a # sign only * signifies a a resident kernel segment. When we * hit one of these we are done reading the * module list. */ have_modules = 1; return(1); } /* Allocate space for the module. */ sym_array_modules = (struct Module *) \ realloc(sym_array_modules, \ (num_modules+1) * sizeof(struct Module)); if ( sym_array_modules == (struct Module *) 0 ) { Syslog(LOG_WARNING, "Cannot allocate Module array.\n"); return(0); } mp = &sym_array_modules[num_modules]; if ( (memfd = open("/dev/kmem", O_RDONLY)) < 0 ) { Syslog(LOG_WARNING, "Error opening /dev/kmem\n"); return(0); } if ( lseek64(memfd, address, SEEK_SET) < 0 ) { Syslog(LOG_WARNING, "Error seeking in /dev/kmem\n"); Syslog(LOG_WARNING, "Symbol %s, value %08x\n", symbol, address); return(0); } if ( read(memfd, \ (char *)&sym_array_modules[num_modules].module, \ sizeof(struct module)) < 0 ) { Syslog(LOG_WARNING, "Error reading module " "descriptor.\n"); return(0); } close(memfd); /* Save the module name. */ mp->name = (char *) malloc(strlen(&symbol[1]) + 1); if ( mp->name == (char *) 0 ) return(0); strcpy(mp->name, &symbol[1]); mp->num_syms = 0; mp->sym_array = (struct sym_table *) 0; ++num_modules; return(1); } else { if (num_modules > 0) mp = &sym_array_modules[num_modules - 1]; else mp = &sym_array_modules[0]; AddSymbol(mp, address, symbol); } return(1); } /************************************************************************** * Function: AddSymbol * * Purpose: This function is responsible for adding a symbol name * and its address to the symbol table. * * Arguements: (struct Module *) mp, (unsigned long) address, (char *) symbol * * mp:-> A pointer to the module which the symbol is * to be added to. * * address:-> The address of the symbol. * * symbol:-> The name of the symbol. * * Return: int * * A boolean value is assumed. True if the addition is * successful. False if not. **************************************************************************/ static int AddSymbol(mp, address, symbol) struct Module *mp; unsigned long address; char *symbol; { auto int tmp; /* Allocate space for the symbol table entry. */ mp->sym_array = (struct sym_table *) realloc(mp->sym_array, \ (mp->num_syms+1) * sizeof(struct sym_table)); if ( mp->sym_array == (struct sym_table *) 0 ) return(0); /* Then the space for the symbol. */ tmp = strlen(symbol); tmp += (strlen(mp->name) + 1); mp->sym_array[mp->num_syms].name = (char *) malloc(tmp + 1); if ( mp->sym_array[mp->num_syms].name == (char *) 0 ) return(0); memset(mp->sym_array[mp->num_syms].name, '\0', tmp + 1); /* Stuff interesting information into the module. */ mp->sym_array[mp->num_syms].value = address; strcpy(mp->sym_array[mp->num_syms].name, mp->name); strcat(mp->sym_array[mp->num_syms].name, ":"); strcat(mp->sym_array[mp->num_syms].name, symbol); ++mp->num_syms; return(1); } /************************************************************************** * Function: LookupModuleSymbol * * Purpose: Find the symbol which is related to the given address from * a kernel module. * * Arguements: (long int) value, (struct symbol *) sym * * value:-> The address to be located. * * sym:-> A pointer to a structure which will be * loaded with the symbol's parameters. * * Return: (char *) * * If a match cannot be found a diagnostic string is printed. * If a match is found the pointer to the symbolic name most * closely matching the address is returned. **************************************************************************/ extern char * LookupModuleSymbol(value, sym) unsigned long value; struct symbol *sym; { auto int nmod, nsym; auto struct sym_table *last; auto struct Module *mp; sym->size = 0; sym->offset = 0; if ( num_modules == 0 ) return((char *) 0); for(nmod= 0; nmod < num_modules; ++nmod) { mp = &sym_array_modules[nmod]; /* * Run through the list of symbols in this module and * see if the address can be resolved. */ for(nsym= 1, last = &mp->sym_array[0]; nsym < mp->num_syms; ++nsym) { if ( mp->sym_array[nsym].value > value ) { sym->offset = value - last->value; sym->size = mp->sym_array[nsym].value - \ last->value; return(last->name); } last = &mp->sym_array[nsym]; } /* * At this stage of the game we still cannot give up the * ghost. There is the possibility that the address is * from a module which has no symbols registered with * the kernel. The solution is to compare the address * against the starting address and extant of the module * If it is in this range we can at least return the * name of the module. */ #if LINUX_VERSION_CODE < 0x20112 if ( (void *) value >= mp->module.addr && (void *) value <= (mp->module.addr + \ mp->module.size * 4096) ) #else if ( value >= mp->module_info.addr && value <= (mp->module_info.addr + \ mp->module.size * 4096) ) #endif { /* * A special case needs to be checked for. The above * conditional tells us that we are within the * extant of this module but symbol lookup has * failed. * * We need to check to see if any symbols have * been defined in this module. If there have been * symbols defined the assumption must be made that * the faulting address lies somewhere beyond the * last symbol. About the only thing we can do * at this point is use an offset from this * symbol. */ if ( mp->num_syms > 0 ) { last = &mp->sym_array[mp->num_syms - 1]; #if LINUX_VERSION_CODE < 0x20112 sym->size = (int) mp->module.addr + \ (mp->module.size * 4096) - value; #else sym->size = (int) mp->module_info.addr + \ (mp->module.size * 4096) - value; #endif sym->offset = value - last->value; return(last->name); } /* * There were no symbols defined for this module. * Return the module name and the offset of the * faulting address in the module. */ sym->size = mp->module.size * 4096; #if LINUX_VERSION_CODE < 0x20112 sym->offset = (void *) value - mp->module.addr; #else sym->offset = value - mp->module_info.addr; #endif return(mp->name); } } /* It has been a hopeless exercise. */ return((char *) 0); } /* * Setting the -DTEST define enables the following code fragment to * be compiled. This produces a small standalone program which will * dump the current kernel symbol table. */ #if defined(TEST) #include extern int main(int, char **); int main(argc, argv) int argc; char *argv[]; { auto int lp, syms; if ( !InitMsyms() ) { fprintf(stderr, "Cannot load module symbols.\n"); return(1); } printf("Number of modules: %d\n\n", num_modules); for(lp= 0; lp < num_modules; ++lp) { printf("Module #%d = %s, Number of symbols = %d\n", lp + 1, \ sym_array_modules[lp].name, \ sym_array_modules[lp].num_syms); for (syms= 0; syms < sym_array_modules[lp].num_syms; ++syms) { printf("\tSymbol #%d\n", syms + 1); printf("\tName: %s\n", \ sym_array_modules[lp].sym_array[syms].name); printf("\tAddress: %lx\n\n", \ sym_array_modules[lp].sym_array[syms].value); } } FreeModules(); return(0); } extern void Syslog(int priority, char *fmt, ...) { va_list ap; va_start(ap, fmt); fprintf(stdout, "Pr: %d, ", priority); vfprintf(stdout, fmt, ap); va_end(ap); fputc('\n', stdout); return; } #endif