diff options
Diffstat (limited to 'src/backend/utils/fmgr/dfmgr.c')
| -rw-r--r-- | src/backend/utils/fmgr/dfmgr.c | 700 |
1 files changed, 700 insertions, 0 deletions
diff --git a/src/backend/utils/fmgr/dfmgr.c b/src/backend/utils/fmgr/dfmgr.c new file mode 100644 index 0000000..7f9ea97 --- /dev/null +++ b/src/backend/utils/fmgr/dfmgr.c @@ -0,0 +1,700 @@ +/*------------------------------------------------------------------------- + * + * dfmgr.c + * Dynamic function manager code. + * + * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * + * IDENTIFICATION + * src/backend/utils/fmgr/dfmgr.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include <sys/stat.h> + +#ifdef HAVE_DLOPEN +#include <dlfcn.h> + +/* + * On macOS, <dlfcn.h> insists on including <stdbool.h>. If we're not + * using stdbool, undef bool to undo the damage. + */ +#ifndef PG_USE_STDBOOL +#ifdef bool +#undef bool +#endif +#endif +#endif /* HAVE_DLOPEN */ + +#include "fmgr.h" +#include "lib/stringinfo.h" +#include "miscadmin.h" +#include "storage/shmem.h" +#include "utils/hsearch.h" + + +/* signature for PostgreSQL-specific library init function */ +typedef void (*PG_init_t) (void); + +/* hashtable entry for rendezvous variables */ +typedef struct +{ + char varName[NAMEDATALEN]; /* hash key (must be first) */ + void *varValue; +} rendezvousHashEntry; + +/* + * List of dynamically loaded files (kept in malloc'd memory). + */ + +typedef struct df_files +{ + struct df_files *next; /* List link */ + dev_t device; /* Device file is on */ +#ifndef WIN32 /* ensures we never again depend on this under + * win32 */ + ino_t inode; /* Inode number of file */ +#endif + void *handle; /* a handle for pg_dl* functions */ + char filename[FLEXIBLE_ARRAY_MEMBER]; /* Full pathname of file */ +} DynamicFileList; + +static DynamicFileList *file_list = NULL; +static DynamicFileList *file_tail = NULL; + +/* stat() call under Win32 returns an st_ino field, but it has no meaning */ +#ifndef WIN32 +#define SAME_INODE(A,B) ((A).st_ino == (B).inode && (A).st_dev == (B).device) +#else +#define SAME_INODE(A,B) false +#endif + +char *Dynamic_library_path; + +static void *internal_load_library(const char *libname); +static void incompatible_module_error(const char *libname, + const Pg_magic_struct *module_magic_data) pg_attribute_noreturn(); +static bool file_exists(const char *name); +static char *expand_dynamic_library_name(const char *name); +static void check_restricted_library_name(const char *name); +static char *substitute_libpath_macro(const char *name); +static char *find_in_dynamic_libpath(const char *basename); + +/* Magic structure that module needs to match to be accepted */ +static const Pg_magic_struct magic_data = PG_MODULE_MAGIC_DATA; + + +/* + * Load the specified dynamic-link library file, and look for a function + * named funcname in it. + * + * If the function is not found, we raise an error if signalNotFound is true, + * else return NULL. Note that errors in loading the library + * will provoke ereport() regardless of signalNotFound. + * + * If filehandle is not NULL, then *filehandle will be set to a handle + * identifying the library file. The filehandle can be used with + * lookup_external_function to lookup additional functions in the same file + * at less cost than repeating load_external_function. + */ +void * +load_external_function(const char *filename, const char *funcname, + bool signalNotFound, void **filehandle) +{ + char *fullname; + void *lib_handle; + void *retval; + + /* Expand the possibly-abbreviated filename to an exact path name */ + fullname = expand_dynamic_library_name(filename); + + /* Load the shared library, unless we already did */ + lib_handle = internal_load_library(fullname); + + /* Return handle if caller wants it */ + if (filehandle) + *filehandle = lib_handle; + + /* Look up the function within the library. */ + retval = dlsym(lib_handle, funcname); + + if (retval == NULL && signalNotFound) + ereport(ERROR, + (errcode(ERRCODE_UNDEFINED_FUNCTION), + errmsg("could not find function \"%s\" in file \"%s\"", + funcname, fullname))); + + pfree(fullname); + return retval; +} + +/* + * This function loads a shlib file without looking up any particular + * function in it. If the same shlib has previously been loaded, + * unload and reload it. + * + * When 'restricted' is true, only libraries in the presumed-secure + * directory $libdir/plugins may be referenced. + */ +void +load_file(const char *filename, bool restricted) +{ + char *fullname; + + /* Apply security restriction if requested */ + if (restricted) + check_restricted_library_name(filename); + + /* Expand the possibly-abbreviated filename to an exact path name */ + fullname = expand_dynamic_library_name(filename); + + /* Load the shared library */ + (void) internal_load_library(fullname); + + pfree(fullname); +} + +/* + * Lookup a function whose library file is already loaded. + * Return NULL if not found. + */ +void * +lookup_external_function(void *filehandle, const char *funcname) +{ + return dlsym(filehandle, funcname); +} + + +/* + * Load the specified dynamic-link library file, unless it already is + * loaded. Return the pg_dl* handle for the file. + * + * Note: libname is expected to be an exact name for the library file. + * + * NB: There is presently no way to unload a dynamically loaded file. We might + * add one someday if we can convince ourselves we have safe protocols for un- + * hooking from hook function pointers, releasing custom GUC variables, and + * perhaps other things that are definitely unsafe currently. + */ +static void * +internal_load_library(const char *libname) +{ + DynamicFileList *file_scanner; + PGModuleMagicFunction magic_func; + char *load_error; + struct stat stat_buf; + PG_init_t PG_init; + + /* + * Scan the list of loaded FILES to see if the file has been loaded. + */ + for (file_scanner = file_list; + file_scanner != NULL && + strcmp(libname, file_scanner->filename) != 0; + file_scanner = file_scanner->next) + ; + + if (file_scanner == NULL) + { + /* + * Check for same files - different paths (ie, symlink or link) + */ + if (stat(libname, &stat_buf) == -1) + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not access file \"%s\": %m", + libname))); + + for (file_scanner = file_list; + file_scanner != NULL && + !SAME_INODE(stat_buf, *file_scanner); + file_scanner = file_scanner->next) + ; + } + + if (file_scanner == NULL) + { + /* + * File not loaded yet. + */ + file_scanner = (DynamicFileList *) + malloc(offsetof(DynamicFileList, filename) + strlen(libname) + 1); + if (file_scanner == NULL) + ereport(ERROR, + (errcode(ERRCODE_OUT_OF_MEMORY), + errmsg("out of memory"))); + + MemSet(file_scanner, 0, offsetof(DynamicFileList, filename)); + strcpy(file_scanner->filename, libname); + file_scanner->device = stat_buf.st_dev; +#ifndef WIN32 + file_scanner->inode = stat_buf.st_ino; +#endif + file_scanner->next = NULL; + + file_scanner->handle = dlopen(file_scanner->filename, RTLD_NOW | RTLD_GLOBAL); + if (file_scanner->handle == NULL) + { + load_error = dlerror(); + free((char *) file_scanner); + /* errcode_for_file_access might not be appropriate here? */ + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not load library \"%s\": %s", + libname, load_error))); + } + + /* Check the magic function to determine compatibility */ + magic_func = (PGModuleMagicFunction) + dlsym(file_scanner->handle, PG_MAGIC_FUNCTION_NAME_STRING); + if (magic_func) + { + const Pg_magic_struct *magic_data_ptr = (*magic_func) (); + + if (magic_data_ptr->len != magic_data.len || + memcmp(magic_data_ptr, &magic_data, magic_data.len) != 0) + { + /* copy data block before unlinking library */ + Pg_magic_struct module_magic_data = *magic_data_ptr; + + /* try to close library */ + dlclose(file_scanner->handle); + free((char *) file_scanner); + + /* issue suitable complaint */ + incompatible_module_error(libname, &module_magic_data); + } + } + else + { + /* try to close library */ + dlclose(file_scanner->handle); + free((char *) file_scanner); + /* complain */ + ereport(ERROR, + (errmsg("incompatible library \"%s\": missing magic block", + libname), + errhint("Extension libraries are required to use the PG_MODULE_MAGIC macro."))); + } + + /* + * If the library has a _PG_init() function, call it. + */ + PG_init = (PG_init_t) dlsym(file_scanner->handle, "_PG_init"); + if (PG_init) + (*PG_init) (); + + /* OK to link it into list */ + if (file_list == NULL) + file_list = file_scanner; + else + file_tail->next = file_scanner; + file_tail = file_scanner; + } + + return file_scanner->handle; +} + +/* + * Report a suitable error for an incompatible magic block. + */ +static void +incompatible_module_error(const char *libname, + const Pg_magic_struct *module_magic_data) +{ + StringInfoData details; + + /* + * If the version doesn't match, just report that, because the rest of the + * block might not even have the fields we expect. + */ + if (magic_data.version != module_magic_data->version) + { + char library_version[32]; + + if (module_magic_data->version >= 1000) + snprintf(library_version, sizeof(library_version), "%d", + module_magic_data->version / 100); + else + snprintf(library_version, sizeof(library_version), "%d.%d", + module_magic_data->version / 100, + module_magic_data->version % 100); + ereport(ERROR, + (errmsg("incompatible library \"%s\": version mismatch", + libname), + errdetail("Server is version %d, library is version %s.", + magic_data.version / 100, library_version))); + } + + /* + * Similarly, if the ABI extra field doesn't match, error out. Other + * fields below might also mismatch, but that isn't useful information if + * you're using the wrong product altogether. + */ + if (strcmp(module_magic_data->abi_extra, magic_data.abi_extra) != 0) + { + ereport(ERROR, + (errmsg("incompatible library \"%s\": ABI mismatch", + libname), + errdetail("Server has ABI \"%s\", library has \"%s\".", + magic_data.abi_extra, + module_magic_data->abi_extra))); + } + + /* + * Otherwise, spell out which fields don't agree. + * + * XXX this code has to be adjusted any time the set of fields in a magic + * block change! + */ + initStringInfo(&details); + + if (module_magic_data->funcmaxargs != magic_data.funcmaxargs) + { + if (details.len) + appendStringInfoChar(&details, '\n'); + appendStringInfo(&details, + _("Server has FUNC_MAX_ARGS = %d, library has %d."), + magic_data.funcmaxargs, + module_magic_data->funcmaxargs); + } + if (module_magic_data->indexmaxkeys != magic_data.indexmaxkeys) + { + if (details.len) + appendStringInfoChar(&details, '\n'); + appendStringInfo(&details, + _("Server has INDEX_MAX_KEYS = %d, library has %d."), + magic_data.indexmaxkeys, + module_magic_data->indexmaxkeys); + } + if (module_magic_data->namedatalen != magic_data.namedatalen) + { + if (details.len) + appendStringInfoChar(&details, '\n'); + appendStringInfo(&details, + _("Server has NAMEDATALEN = %d, library has %d."), + magic_data.namedatalen, + module_magic_data->namedatalen); + } + if (module_magic_data->float8byval != magic_data.float8byval) + { + if (details.len) + appendStringInfoChar(&details, '\n'); + appendStringInfo(&details, + _("Server has FLOAT8PASSBYVAL = %s, library has %s."), + magic_data.float8byval ? "true" : "false", + module_magic_data->float8byval ? "true" : "false"); + } + + if (details.len == 0) + appendStringInfoString(&details, + _("Magic block has unexpected length or padding difference.")); + + ereport(ERROR, + (errmsg("incompatible library \"%s\": magic block mismatch", + libname), + errdetail_internal("%s", details.data))); +} + +static bool +file_exists(const char *name) +{ + struct stat st; + + AssertArg(name != NULL); + + if (stat(name, &st) == 0) + return !S_ISDIR(st.st_mode); + else if (!(errno == ENOENT || errno == ENOTDIR || errno == EACCES)) + ereport(ERROR, + (errcode_for_file_access(), + errmsg("could not access file \"%s\": %m", name))); + + return false; +} + + +/* + * If name contains a slash, check if the file exists, if so return + * the name. Else (no slash) try to expand using search path (see + * find_in_dynamic_libpath below); if that works, return the fully + * expanded file name. If the previous failed, append DLSUFFIX and + * try again. If all fails, just return the original name. + * + * The result will always be freshly palloc'd. + */ +static char * +expand_dynamic_library_name(const char *name) +{ + bool have_slash; + char *new; + char *full; + + AssertArg(name); + + have_slash = (first_dir_separator(name) != NULL); + + if (!have_slash) + { + full = find_in_dynamic_libpath(name); + if (full) + return full; + } + else + { + full = substitute_libpath_macro(name); + if (file_exists(full)) + return full; + pfree(full); + } + + new = psprintf("%s%s", name, DLSUFFIX); + + if (!have_slash) + { + full = find_in_dynamic_libpath(new); + pfree(new); + if (full) + return full; + } + else + { + full = substitute_libpath_macro(new); + pfree(new); + if (file_exists(full)) + return full; + pfree(full); + } + + /* + * If we can't find the file, just return the string as-is. The ensuing + * load attempt will fail and report a suitable message. + */ + return pstrdup(name); +} + +/* + * Check a restricted library name. It must begin with "$libdir/plugins/" + * and there must not be any directory separators after that (this is + * sufficient to prevent ".." style attacks). + */ +static void +check_restricted_library_name(const char *name) +{ + if (strncmp(name, "$libdir/plugins/", 16) != 0 || + first_dir_separator(name + 16) != NULL) + ereport(ERROR, + (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE), + errmsg("access to library \"%s\" is not allowed", + name))); +} + +/* + * Substitute for any macros appearing in the given string. + * Result is always freshly palloc'd. + */ +static char * +substitute_libpath_macro(const char *name) +{ + const char *sep_ptr; + + AssertArg(name != NULL); + + /* Currently, we only recognize $libdir at the start of the string */ + if (name[0] != '$') + return pstrdup(name); + + if ((sep_ptr = first_dir_separator(name)) == NULL) + sep_ptr = name + strlen(name); + + if (strlen("$libdir") != sep_ptr - name || + strncmp(name, "$libdir", strlen("$libdir")) != 0) + ereport(ERROR, + (errcode(ERRCODE_INVALID_NAME), + errmsg("invalid macro name in dynamic library path: %s", + name))); + + return psprintf("%s%s", pkglib_path, sep_ptr); +} + + +/* + * Search for a file called 'basename' in the colon-separated search + * path Dynamic_library_path. If the file is found, the full file name + * is returned in freshly palloc'd memory. If the file is not found, + * return NULL. + */ +static char * +find_in_dynamic_libpath(const char *basename) +{ + const char *p; + size_t baselen; + + AssertArg(basename != NULL); + AssertArg(first_dir_separator(basename) == NULL); + AssertState(Dynamic_library_path != NULL); + + p = Dynamic_library_path; + if (strlen(p) == 0) + return NULL; + + baselen = strlen(basename); + + for (;;) + { + size_t len; + char *piece; + char *mangled; + char *full; + + piece = first_path_var_separator(p); + if (piece == p) + ereport(ERROR, + (errcode(ERRCODE_INVALID_NAME), + errmsg("zero-length component in parameter \"dynamic_library_path\""))); + + if (piece == NULL) + len = strlen(p); + else + len = piece - p; + + piece = palloc(len + 1); + strlcpy(piece, p, len + 1); + + mangled = substitute_libpath_macro(piece); + pfree(piece); + + canonicalize_path(mangled); + + /* only absolute paths */ + if (!is_absolute_path(mangled)) + ereport(ERROR, + (errcode(ERRCODE_INVALID_NAME), + errmsg("component in parameter \"dynamic_library_path\" is not an absolute path"))); + + full = palloc(strlen(mangled) + 1 + baselen + 1); + sprintf(full, "%s/%s", mangled, basename); + pfree(mangled); + + elog(DEBUG3, "find_in_dynamic_libpath: trying \"%s\"", full); + + if (file_exists(full)) + return full; + + pfree(full); + + if (p[len] == '\0') + break; + else + p += len + 1; + } + + return NULL; +} + + +/* + * Find (or create) a rendezvous variable that one dynamically + * loaded library can use to meet up with another. + * + * On the first call of this function for a particular varName, + * a "rendezvous variable" is created with the given name. + * The value of the variable is a void pointer (initially set to NULL). + * Subsequent calls with the same varName just return the address of + * the existing variable. Once created, a rendezvous variable lasts + * for the life of the process. + * + * Dynamically loaded libraries can use rendezvous variables + * to find each other and share information: they just need to agree + * on the variable name and the data it will point to. + */ +void ** +find_rendezvous_variable(const char *varName) +{ + static HTAB *rendezvousHash = NULL; + + rendezvousHashEntry *hentry; + bool found; + + /* Create a hashtable if we haven't already done so in this process */ + if (rendezvousHash == NULL) + { + HASHCTL ctl; + + ctl.keysize = NAMEDATALEN; + ctl.entrysize = sizeof(rendezvousHashEntry); + rendezvousHash = hash_create("Rendezvous variable hash", + 16, + &ctl, + HASH_ELEM | HASH_STRINGS); + } + + /* Find or create the hashtable entry for this varName */ + hentry = (rendezvousHashEntry *) hash_search(rendezvousHash, + varName, + HASH_ENTER, + &found); + + /* Initialize to NULL if first time */ + if (!found) + hentry->varValue = NULL; + + return &hentry->varValue; +} + +/* + * Estimate the amount of space needed to serialize the list of libraries + * we have loaded. + */ +Size +EstimateLibraryStateSpace(void) +{ + DynamicFileList *file_scanner; + Size size = 1; + + for (file_scanner = file_list; + file_scanner != NULL; + file_scanner = file_scanner->next) + size = add_size(size, strlen(file_scanner->filename) + 1); + + return size; +} + +/* + * Serialize the list of libraries we have loaded to a chunk of memory. + */ +void +SerializeLibraryState(Size maxsize, char *start_address) +{ + DynamicFileList *file_scanner; + + for (file_scanner = file_list; + file_scanner != NULL; + file_scanner = file_scanner->next) + { + Size len; + + len = strlcpy(start_address, file_scanner->filename, maxsize) + 1; + Assert(len < maxsize); + maxsize -= len; + start_address += len; + } + start_address[0] = '\0'; +} + +/* + * Load every library the serializing backend had loaded. + */ +void +RestoreLibraryState(char *start_address) +{ + while (*start_address != '\0') + { + internal_load_library(start_address); + start_address += strlen(start_address) + 1; + } +} |