usr/src/lib/libdtrace/common/dlink_audit.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * This file and its contents are supplied under the terms of the
   5  * Common Development and Distribution License ("CDDL"), version 1.0.
   6  * You may only use this file in accordance with the terms of version
   7  * 1.0 of the CDDL.
   8  *
   9  * A full copy of the text of the CDDL should have accompanied this
  10  * source.  A copy of the CDDL is also available via the Internet at
  11  * http://www.illumos.org/license/CDDL.
  12  *
  13  * CDDL HEADER END
  14  */
  15
  16 /*
  17  * Copyright (c) 2012 by Delphix. All rights reserved.
  18  */
  19
  20 /*
  21  * This file implements an audit library that can be used to force the loading
  22  * of helper providers. The default disposition for a helper provider -- USDT
  23  * and ustack helpers -- is to load itself from it's containing object's .init
  24  * section. In cases where startup time is deemed critical, USDT authors can
  25  * use the -xlazyload option to dtrace(1M) to disable automatic loading (it's
  26  * difficult to make the case for the utility of this feature for anything
  27  * other than libc which, indeed, was the sole motivation). If a binary has
  28  * been compiled with automatic loading disabled, this audit library may be
  29  * used to force automatic loading:
  30  *
  31  *      LD_AUDIT_32=/usr/lib/dtrace/libdaudit.so
  32  *      LD_AUDIT_64=/usr/lib/dtrace/64/libdaudit.so
  33  */
  34
  35 #include <link.h>
  36 #include <stdio.h>
  37 #include <libproc.h>
  38 #include <strings.h>
  39
  40 #include <dlink.h>
  41
  42 typedef struct obj_list {
  43         struct obj_list *ol_next;
  44         char *ol_name;
  45         uintptr_t ol_addr;
  46         Lmid_t ol_lmid;
  47 } obj_list_t;
  48
  49 static obj_list_t *list;
  50
  51 #pragma init(dtrace_daudit_init)
  52 static void
  53 dtrace_daudit_init(void)
  54 {
  55         dtrace_link_init();
  56 }
  57
  58 /*ARGSUSED*/
  59 uint_t
  60 la_version(uint_t version)
  61 {
  62         return (LAV_CURRENT);
  63 }
  64
  65 /*
  66  * Record objects into our linked list as they're loaded.
  67  */
  68 /*ARGSUSED*/
  69 uint_t
  70 la_objopen(Link_map *lmp, Lmid_t lmid, uintptr_t *cookie)
  71 {
  72         obj_list_t *node;
  73
  74         /*
  75          * If we can't allocate the next node in our list, we'll try to emit a
  76          * message, but it's possible that might fail as well.
  77          */
  78         if ((node = malloc(sizeof (obj_list_t))) == NULL) {
  79                 dprintf(0, "libdaudit: failed to allocate");
  80                 return (0);
  81         }
  82         node->ol_next = list;
  83         node->ol_name = strdup(lmp->l_name);
  84         node->ol_addr = lmp->l_addr;
  85         node->ol_lmid = lmid;
  86         list = node;
  87
  88         return (0);
  89 }
  90
  91 /*
  92  * Once the link maps have reached a consistent state, process the list of
  93  * objects that were loaded. We need to use libproc to search for the
  94  * ___SUNW_dof symbol rather than dlsym(3C) since the symbol is not in the
  95  * dynamic (run-time) symbol table (though it is, of course, in the symtab).
  96  * Once we find it, we ioctl(2) it to the kernel just as we would have from
  97  * the .init section if automatic loading were enabled.
  98  */
  99 /*ARGSUSED*/
 100 void
 101 la_activity(uintptr_t *cookie, uint_t flags)
 102 {
 103         struct ps_prochandle *P;
 104         int err, ret;
 105         GElf_Sym sym;
 106
 107         if (flags != LA_ACT_CONSISTENT)
 108                 return;
 109
 110         while (list != NULL) {
 111                 obj_list_t *node = list;
 112                 char *name = node->ol_name;
 113
 114                 list = node->ol_next;
 115
 116                 P = Pgrab(getpid(), PGRAB_RDONLY, &err);
 117                 ret = Plookup_by_name(P, name, "___SUNW_dof", &sym);
 118                 Prelease(P, 0);
 119
 120                 if (ret == 0) {
 121                         dtrace_link_dof((void *)(uintptr_t)sym.st_value,
 122                             node->ol_lmid, node->ol_name, node->ol_addr);
 123                 }
 124
 125                 free(node->ol_name);
 126                 free(node);
 127         }
 128 }