runtime/sym.c - systemtap

Functions defined

Macros defined

Source code

/* -*- linux-c -*-
 * Symbolic Lookup Functions
 * Copyright (C) 2005-2014 Red Hat Inc.
 * Copyright (C) 2006 Intel Corporation.
 *
 * This file is part of systemtap, and is free software.  You can
 * redistribute it and/or modify it under the terms of the GNU General
 * Public License (GPL); either version 2, or (at your option) any
 * later version.
 */

#ifndef _STP_SYM_C_
‌#define _STP_SYM_C_

#include "sym.h"
#include "vma.c"
#include "stp_string.c"
#include <asm/unaligned.h>
#include <asm/uaccess.h>
#include <linux/list.h>
#include <linux/module.h>
#ifdef STAPCONF_PROBE_KERNEL
#include <linux/uaccess.h>
#endif

/* Returns absolute address of offset into kernel module/section.
   Returns zero when module and section couldn't be found
   (aren't in memory yet). */
‌static unsigned long _stp_kmodule_relocate(const char *module,
                       const char *section,
                       unsigned long offset)
{
  unsigned i, j;

  dbug_sym(1, "%s, %s, %lx\n", module, section, offset);

  /* absolute, unrelocated address */
  if (!module || !strcmp(section, "")
      ||_stp_num_modules == 0) {
    return offset;
  }

  for (i = 0; i < _stp_num_modules; i++) {
    struct _stp_module *m = _stp_modules[i];
    if (strcmp(module, m->name)) /* duplication apprx. not possible for kernel */
      continue;

    for (j = 0; j < m->num_sections; j++) {
      struct _stp_section *s = &m->sections[j];
      if (!strcmp(section, s->name)) {
    /* mod and sec name match. tsk should match dynamic/static. */
    if (s->static_addr != 0) {
      unsigned long addr = offset + s->static_addr;
      dbug_sym(1, "address=%lx\n", addr);
      return addr;
    } else {
      /* static section, not in memory yet? */
      dbug_sym(1, "section %s, not in memory yet?", s->name);
      return 0;
    }
      }
    }
  }

  return 0;
}

‌static unsigned long _stp_umodule_relocate(const char *path,
                       unsigned long offset,
                       struct task_struct *tsk)
{
  unsigned i;
  unsigned long vm_start = 0;

  dbug_sym(1, "[%d] %s, %lx\n", tsk->pid, path, offset);

  for (i = 0; i < _stp_num_modules; i++) {
    struct _stp_module *m = _stp_modules[i];

    if (strcmp(path, m->path)
        || m->num_sections != 1)
      continue;

    if (!strcmp(m->sections[0].name, ".absolute"))
      return offset;
    if (strcmp(m->sections[0].name, ".dynamic"))
      continue;

    if (stap_find_vma_map_info_user(tsk->group_leader, m,
                    &vm_start, NULL, NULL) == 0) {
      offset += vm_start;
      dbug_sym(1, "address=%lx\n", offset);
      return offset;
    }
  }

  return 0;
}

/* Return (kernel) module owner and, if sec != NULL, fills in closest
   section of the address if found, return NULL otherwise. */
‌static struct _stp_module *_stp_kmod_sec_lookup(unsigned long addr,
                        struct _stp_section **sec)
{
  unsigned midx = 0;

  for (midx = 0; midx < _stp_num_modules; midx++)
    {
      unsigned secidx;
      for (secidx = 0; secidx < _stp_modules[midx]->num_sections; secidx++)
    {
      unsigned long sec_addr;
      unsigned long sec_size;
      sec_addr = _stp_modules[midx]->sections[secidx].static_addr;
      sec_size = _stp_modules[midx]->sections[secidx].size;
      if (addr >= sec_addr && addr < sec_addr + sec_size)
            {
          if (sec)
        *sec = & _stp_modules[midx]->sections[secidx];
          return _stp_modules[midx];
        }
    }
      }
  return NULL;
}

/* Return (user) module in which the the given addr falls.  Returns
   NULL when no module can be found that contains the addr.  Fills in
   vm_start (addr where module is mapped in) and (base) name of module
   when given.  Note that user modules always have exactly one section
   (.dynamic or .absolute). */
‌static struct _stp_module *_stp_umod_lookup(unsigned long addr,
                        struct task_struct *task,
                        const char **name,
                        unsigned long *vm_start,
                        unsigned long *vm_end)
{
  void *user = NULL;
#ifdef CONFIG_COMPAT
        /* Handle 32bit signed values in 64bit longs, chop off top bits. */
        if (test_tsk_thread_flag(task, TIF_32BIT))
          addr &= ((compat_ulong_t) ~0);
#endif
  if (stap_find_vma_map_info(task->group_leader, addr,
                 vm_start, vm_end, name, &user) == 0)
    if (user != NULL)
      {
    struct _stp_module *m = (struct _stp_module *)user;
    dbug_sym(1, "found module %s at 0x%lx\n", m->path,
         vm_start ? *vm_start : 0);
    return m;
      }
  return NULL;
}

‌static const char *_stp_kallsyms_lookup(unsigned long addr,
                                        unsigned long *symbolsize,
                                        unsigned long *offset,
                                        const char **modname,
                                        /* char ** secname? */
                    struct task_struct *task)
{
    struct _stp_module *m = NULL;
    struct _stp_section *sec = NULL;
    struct _stp_symbol *s = NULL;
    unsigned end, begin = 0;
    unsigned long rel_addr = 0;

    if (addr == 0)
      return NULL;

    if (task)
      {
        unsigned long vm_start = 0;
        unsigned long vm_end = 0;
#ifdef CONFIG_COMPAT
        /* Handle 32bit signed values in 64bit longs, chop off top bits.
           _stp_umod_lookup does the same, but we need it here for the
           binary search on addr below. */
        if (test_tsk_thread_flag(task, TIF_32BIT))
          addr &= ((compat_ulong_t) ~0);
#endif
        m = _stp_umod_lookup(addr, task, modname, &vm_start, &vm_end);
        if (m)
          {
        sec = &m->sections[0];
        /* XXX .absolute sections really shouldn't be here... */
        if (strcmp(".dynamic", m->sections[0].name) == 0)
          rel_addr = addr - vm_start;
        else
          rel_addr = addr;
          }
        if (modname && *modname)
          {
        /* In case no symbol is found, fill in based on module. */
        if (offset)
          *offset = addr - vm_start;
        if (symbolsize)
          *symbolsize = vm_end - vm_start;
          }
      }
    else
      {
        m = _stp_kmod_sec_lookup(addr, &sec);
        if (m)
          {
            rel_addr = addr - sec->static_addr;
        if (modname)
          *modname = m->name;
          }
      }

        if (unlikely (m == NULL || sec == NULL))
          return NULL;

        /* NB: relativize the address to the section. */
        addr = rel_addr;
    end = sec->num_symbols;

    /* binary search for symbols within the module */
    do {
        unsigned mid = (begin + end) / 2;
        if (addr < sec->symbols[mid].addr)
            end = mid;
        else
            begin = mid;
    } while (begin + 1 < end);
    /* result index in $begin */

    s = & sec->symbols[begin];
    if (likely(addr >= s->addr)) {
        if (offset)
            *offset = addr - s->addr;
                /* We could also pass sec->name here. */
        if (symbolsize) {
            if ((begin + 1) < sec->num_symbols)
                *symbolsize = sec->symbols[begin + 1].addr - s->addr;
            else
                *symbolsize = 0;
            // NB: This is only a heuristic.  Sometimes there are large
            // gaps between text areas of modules.
        }
        return s->symbol;
    }
    return NULL;
}

‌static int _stp_build_id_check (struct _stp_module *m,
                unsigned long notes_addr,
                struct task_struct *tsk)
{
  int j;

  for (j = 0; j < m->build_id_len; j++) {
    /* Use set_fs / get_user to access conceivably invalid addresses.
     * If loc2c-runtime.h were more easily usable, a deref() loop
     * could do it too. */
    mm_segment_t oldfs = get_fs();
    int rc;
    unsigned char theory, practice = 0;

#ifdef STAPCONF_PROBE_KERNEL
    if (!tsk) {
      theory = m->build_id_bits[j];
      set_fs(KERNEL_DS);
      rc = probe_kernel_read(&practice, (void*)(notes_addr + j), 1);
    }
    else
#endif
    {
      theory = m->build_id_bits[j];
      set_fs (tsk ? USER_DS : KERNEL_DS);

      /*
       * Why check CONFIG_UTRACE here? If we're using real in-kernel
       * utrace, we can always just call get_user() (since we're
       * either reading kernel memory or tsk == current).
       *
       * Since we're only reading here, we can call
       * __access_process_vm_noflush(), which only calls things that
       * are exported.
       */
#ifdef CONFIG_UTRACE
      rc = get_user(practice, ((unsigned char*)(void*)(notes_addr + j)));
#else
      if (!tsk || tsk == current) {
    rc = get_user(practice, ((unsigned char*)(void*)(notes_addr + j)));
      }
      else {
    rc = (__access_process_vm_noflush(tsk, (notes_addr + j), &practice,
                      1, 0) != 1);
      }
#endif
    }
    set_fs(oldfs);

    if (rc || (theory != practice)) {
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,27)
      _stp_error ("Build-id mismatch [man error::buildid]: \"%s\" byte %d (0x%02x vs 0x%02x) address %#lx rc %d\n",
          m->path, j, theory, practice, notes_addr, rc);
      return 1;
#else
      /* This branch is a surrogate for kernels affected by Fedora bug
       * #465873. */
      _stp_warn (KERN_WARNING
         "Build-id mismatch [man error::buildid]: \"%s\" byte %d (0x%02x vs 0x%02x) rc %d\n",
         m->path, j, theory, practice, rc);
#endif
      break;
    } /* end mismatch */
  } /* end per-byte check loop */
  return 0;
}


/* Validate all-modules + kernel based on build-id (if present).
*  The completed case is the following combination:
*       Debuginfo          Module                     Kernel
*                X                X
*     has build-id/not    unloaded              has build-id/not
*                loaded && (has build-id/not)
*
*  NB: build-id exists only if ld>=2.18 and kernel>= 2.6.23
*/
‌static int _stp_module_check(void)
{
  struct _stp_module *m = NULL;
  unsigned long notes_addr, base_addr;
  unsigned i,j;
  int rc = 0;

#ifdef STP_NO_BUILDID_CHECK
  return 0;
#endif

  for (i = 0; i < _stp_num_modules; i++)
    {
      m = _stp_modules[i];

      if (m->build_id_len > 0 && m->notes_sect != 0) {
          dbug_sym(1, "build-id validation [%s]\n", m->name); /* kernel only */

          /* skip userspace program */
          if (m->name[0] != '/') continue;

          /* notes end address */
          if (!strcmp(m->name, "kernel")) {
              notes_addr = _stp_kmodule_relocate("kernel",
                  "_stext", m->build_id_offset);
              base_addr = _stp_kmodule_relocate("kernel",
                  "_stext", 0);
          } else {
              notes_addr = m->notes_sect + m->build_id_offset;
              base_addr = m->notes_sect;
          }

          if (notes_addr <= base_addr) { /* shouldn't happen */
              _stp_warn ("build-id address %lx <= base %lx\n",
                  notes_addr, base_addr);
              continue;
          }

          rc |=  _stp_build_id_check (m, notes_addr, NULL);
      } /* end checking */
    } /* end loop */

  return rc;
}



/* Iterate over _stp_modules, looking for a kernel module of given
   name.  Run build-id checking for it.  Return 0 on ok. */
‌static int _stp_kmodule_check (const char *name)
{
  struct _stp_module *m = NULL;
  unsigned long notes_addr, base_addr;
  unsigned i,j;

#ifdef STP_NO_BUILDID_CHECK
  return 0;
#endif

  WARN_ON(!name || name[0]=='/'); // non-userspace only

  for (i = 0; i < _stp_num_modules; i++)
    {
      m = _stp_modules[i];

      /* PR16406 must be unique kernel module name (non-/-prefixed path) */
      if (strcmp (name, m->name)) continue;

      if (m->build_id_len > 0 && m->notes_sect != 0) {
          dbug_sym(1, "build-id validation [%s]\n", m->name);

          /* notes end address */
          notes_addr = m->notes_sect + m->build_id_offset;
          base_addr = m->notes_sect;

          if (notes_addr <= base_addr) { /* shouldn't happen */
              _stp_warn ("build-id address %lx < base %lx\n",
                  notes_addr, base_addr);
              continue;
          }
          return _stp_build_id_check (m, notes_addr, NULL);
      } /* end checking */
    } /* end loop */

  return 0; /* not found */
}



/* Validate user module based on build-id (if present) */
‌static int _stp_usermodule_check(struct task_struct *tsk, const char *path_name, unsigned long addr)
{
  struct _stp_module *m = NULL;
  unsigned long notes_addr;
  unsigned i, j;
  unsigned char practice_id_bits[MAXSTRINGLEN];
  unsigned long vm_end = 0;

#ifdef STP_NO_BUILDID_CHECK
  return 0;
#endif

  WARN_ON(!path_name || path_name[0]!='/'); // user-space only

  for (i = 0; i < _stp_num_modules; i++)
    {
      m = _stp_modules[i];

      /* PR16406 must be unique userspace name (/-prefixed path); it's also in m->name */
      if (strcmp(path_name, m->path) != 0) continue;

      if (m->build_id_len > 0) {
    int ret, build_id_len;

    notes_addr = addr + m->build_id_offset /* + m->module_base */;

        dbug_sym(1, "build-id validation [%d %s] address=%#lx build_id_offset=%#lx\n",
                 tsk->pid, m->path, addr, m->build_id_offset);

    if (notes_addr <= addr) {
      _stp_warn ("build-id address %lx < base %lx\n", notes_addr, addr);
      continue;
    }
    return _stp_build_id_check (m, notes_addr, tsk);
      }
    }

  return 0; /* not found */
}


/** Prints an address based on the _STP_SYM flags.
 * @param address The address to lookup.
 * @param task The address to lookup (if NULL lookup kernel/module address).
 * @note Symbolic lookups should not normally be done within
 * a probe because it is too time-consuming. Use at module exit time. */
‌static int _stp_snprint_addr(char *str, size_t len, unsigned long address,
                 int flags, struct task_struct *task)
{
  const char *modname = NULL;
  const char *name = NULL;
  unsigned long offset = 0, size = 0;
  char *exstr, *poststr, *prestr;

  prestr = (flags & _STP_SYM_PRE_SPACE) ? " " : "";
  exstr = (((flags & _STP_SYM_INEXACT) && (flags & _STP_SYM_SYMBOL))
       ? " (inexact)" : "");
  if (flags & _STP_SYM_POST_SPACE)
    poststr = " ";
  else if (flags & _STP_SYM_NEWLINE)
    poststr = "\n";
  else
    poststr = "";

  if (flags & (_STP_SYM_SYMBOL | _STP_SYM_MODULE)) {
    name = _stp_kallsyms_lookup(address, &size, &offset, &modname, task);
    if (name && name[0] == '.')
      name++;
  }

  if (modname && (flags & _STP_SYM_MODULE_BASENAME)) {
     char *slash = strrchr (modname, '/');
     if (slash)
        modname = slash+1;
  }

  if (name && (flags & _STP_SYM_SYMBOL)) {
    if ((flags & _STP_SYM_MODULE) && modname && *modname) {
      if (flags & _STP_SYM_OFFSET) {
    if (flags & _STP_SYM_SIZE) {
      /* symbol, module, offset and size. */
      if (flags & _STP_SYM_HEX_SYMBOL)
        return _stp_snprintf(str, len, "%s%p : %s+%#lx/%#lx [%s]%s%s",
                 prestr, (int64_t) address,
                 name, offset, size, modname,
                 exstr, poststr);
      else
        return _stp_snprintf(str, len, "%s%s+%#lx/%#lx [%s]%s%s",
                 prestr, name, offset, size,
                 modname, exstr, poststr);
    } else {
      /* symbol, module, offset. */
      if (flags & _STP_SYM_HEX_SYMBOL)
        return _stp_snprintf(str, len, "%s%p : %s+%#lx [%s]%s%s",
                 prestr, (int64_t) address,
                 name, offset, modname,
                 exstr, poststr);
      else
        return _stp_snprintf(str, len, "%s%s+%#lx [%s]%s%s",
                 prestr, name, offset,
                 modname, exstr, poststr);
    }
      } else {
    /* symbol plus module */
    if (flags & _STP_SYM_HEX_SYMBOL)
      return _stp_snprintf(str, len, "%s%p : %s [%s]%s%s", prestr,
                   (int64_t) address, name, modname,
                   exstr, poststr);
    else
      return _stp_snprintf(str, len, "%s%s [%s]%s%s", prestr, name,
                   modname, exstr, poststr);
      }
    } else if (flags & _STP_SYM_OFFSET) {
      if (flags & _STP_SYM_SIZE) {
    /* symbol name, offset + size, no module name */
    if (flags & _STP_SYM_HEX_SYMBOL)
      return _stp_snprintf(str, len, "%s%p : %s+%#lx/%#lx%s%s", prestr,
                   (int64_t) address, name, offset,
                   size, exstr, poststr);
    else
      return _stp_snprintf(str, len, "%s%s+%#lx/%#lx%s%s", prestr, name,
                   offset, size, exstr, poststr);
      } else {
    /* symbol name, offset, no module name */
    if (flags & _STP_SYM_HEX_SYMBOL)
      return _stp_snprintf(str, len, "%s%p : %s+%#lx%s%s", prestr,
                   (int64_t) address, name, offset,
                   exstr, poststr);
    else
      return _stp_snprintf(str, len, "%s%s+%#lx%s%s", prestr, name,
                   offset, exstr, poststr);
      }
    } else {
      /* symbol name only */
      if (flags & _STP_SYM_HEX_SYMBOL)
    return _stp_snprintf(str, len, "%s%p : %s%s%s", prestr,
                 (int64_t) address, name, exstr, poststr);
      else
    return _stp_snprintf(str, len, "%s%s%s%s", prestr, name,
                 exstr, poststr);
    }
  } else {
    /* no symbol name */
    if (modname && *modname && (flags & _STP_SYM_MODULE)) {
      if (flags & _STP_SYM_OFFSET) {
        if (flags & _STP_SYM_SIZE) {
          /* hex address, module name, offset + size */
          return _stp_snprintf(str, len, "%s%p [%s+%#lx/%#lx]%s%s", prestr,
                   (int64_t) address, modname, offset,
                   size, exstr, poststr);
        } else {
          /* hex address, module name, offset */
      return _stp_snprintf(str, len, "%s%p [%s+%#lx]%s%s", prestr,
                   (int64_t) address, modname, offset,
                   exstr, poststr);
        }
      } else {
    /* hex address, module name */
        return _stp_snprintf(str, len, "%s%p [%s]%s%s", prestr,
                 (int64_t) address, modname, exstr, poststr);
      }
#ifdef STAPCONF_MODULE_TEXT_ADDRESS
    } if ((flags & _STP_SYM_MODULE) && ! task) {
      /* No symbol, nor module name, but user really wants one, do one
     last try. */
      struct module *ko;
      preempt_disable();
      ko = __module_text_address (address);
      if (ko && ko->name)
    {
      /* hex address, module name */
      int ret = _stp_snprintf(str, len, "%s%p [%s]%s%s", prestr,
                  (int64_t) address, ko->name, exstr, poststr);
      preempt_enable_no_resched();
      return ret;
        }
      preempt_enable_no_resched();
      /* no names, hex only */
      return _stp_snprintf(str, len, "%s%p%s%s", prestr,
               (int64_t) address, exstr, poststr);
#endif
    } else {
      /* no names, hex only */
      return _stp_snprintf(str, len, "%s%p%s%s", prestr,
               (int64_t) address, exstr, poststr);
    }
  }
}

‌static void _stp_print_addr(unsigned long address, int flags,
                struct task_struct *task)
{
  _stp_snprint_addr(NULL, 0, address, flags, task);
}

/** @} */



/* Update the given module/section's offset value.  Assume that there
   is no need for locking or for super performance.  NB: this is only
   for kernel modules, which exist singly at run time.  User-space
   modules (executables, shared libraries) exist at different
   addresses in different processes, so are tracked in the
   _stp_tf_vma_map. */
‌static void _stp_kmodule_update_address(const char* module,
                                        const char* reloc, /* NULL="all" */
                                        unsigned long address)
{
  unsigned mi, si;
  for (mi=0; mi<_stp_num_modules; mi++)
    {
      const char *note_sectname = ".note.gnu.build-id";
      if (strcmp (_stp_modules[mi]->name, module))
        continue;

      if (reloc && !strcmp (note_sectname, reloc)) {
        dbug_sym(1, "module %s special section %s address %#lx\n",
                 _stp_modules[mi]->name,
                 note_sectname,
                 address);
        _stp_modules[mi]->notes_sect = address;   /* cache this particular address  */
      }

      for (si=0; si<_stp_modules[mi]->num_sections; si++)
        {
          if (reloc && strcmp (_stp_modules[mi]->sections[si].name, reloc))
            continue;
          else
            {
              dbug_sym(1, "module %s section %s address %#lx\n",
                       _stp_modules[mi]->name,
                       _stp_modules[mi]->sections[si].name,
                       address);
              _stp_modules[mi]->sections[si].static_addr = address;

              if (reloc) break;
              else continue; /* wildcarded - will have more hits */
            }
        } /* loop over sections */
    } /* loop over modules */
}


#ifndef STAPCONF_KALLSYMS
‌unsigned long kallsyms_lookup_name (const char *name)
{
        /* NB: PR14804: don't use _stp_error here.  It's called too
           early for the actual message buffer goo to be allocated. */
        /* Don't even printk.  A user can't do anything about it. */
        /* printk (KERN_ERR "kallsyms_lookup_name unavailable for %s\n", name); */
        return 0;
}
#endif



#endif /* _STP_SYM_C_ */