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-rw-r--r--elf/dl-map-segments.h153
1 files changed, 153 insertions, 0 deletions
diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h
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+/* Map in a shared object's segments. Generic version.
+ Copyright (C) 1995-2014 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <dl-load.h>
+
+/* This implementation assumes (as does the corresponding implementation
+ of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects
+ are always laid out with all segments contiguous (or with gaps
+ between them small enough that it's preferable to reserve all whole
+ pages inside the gaps with PROT_NONE mappings rather than permitting
+ other use of those parts of the address space). */
+
+static __always_inline const char *
+_dl_map_segments (struct link_map *l, int fd,
+ const ElfW(Ehdr) *header, int type,
+ const struct loadcmd loadcmds[], size_t nloadcmds,
+ const size_t maplength, bool has_holes,
+ struct link_map *loader)
+{
+ const struct loadcmd *c = loadcmds;
+
+ if (__glibc_likely (type == ET_DYN))
+ {
+ /* This is a position-independent shared object. We can let the
+ kernel map it anywhere it likes, but we must have space for all
+ the segments in their specified positions relative to the first.
+ So we map the first segment without MAP_FIXED, but with its
+ extent increased to cover all the segments. Then we remove
+ access from excess portion, and there is known sufficient space
+ there to remap from the later segments.
+
+ As a refinement, sometimes we have an address that we would
+ prefer to map such objects at; but this is only a preference,
+ the OS can do whatever it likes. */
+ ElfW(Addr) mappref
+ = (ELF_PREFERRED_ADDRESS (loader, maplength,
+ c->mapstart & GLRO(dl_use_load_bias))
+ - MAP_BASE_ADDR (l));
+
+ /* Remember which part of the address space this object uses. */
+ l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength,
+ c->prot,
+ MAP_COPY|MAP_FILE,
+ fd, c->mapoff);
+ if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED))
+ return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
+
+ l->l_map_end = l->l_map_start + maplength;
+ l->l_addr = l->l_map_start - c->mapstart;
+
+ if (has_holes)
+ /* Change protection on the excess portion to disallow all access;
+ the portions we do not remap later will be inaccessible as if
+ unallocated. Then jump into the normal segment-mapping loop to
+ handle the portion of the segment past the end of the file
+ mapping. */
+ __mprotect ((caddr_t) (l->l_addr + c->mapend),
+ loadcmds[nloadcmds - 1].mapstart - c->mapend,
+ PROT_NONE);
+
+ l->l_contiguous = 1;
+
+ goto postmap;
+ }
+
+ /* Remember which part of the address space this object uses. */
+ l->l_map_start = c->mapstart + l->l_addr;
+ l->l_map_end = l->l_map_start + maplength;
+ l->l_contiguous = !has_holes;
+
+ while (c < &loadcmds[nloadcmds])
+ {
+ if (c->mapend > c->mapstart
+ /* Map the segment contents from the file. */
+ && (__mmap ((void *) (l->l_addr + c->mapstart),
+ c->mapend - c->mapstart, c->prot,
+ MAP_FIXED|MAP_COPY|MAP_FILE,
+ fd, c->mapoff)
+ == MAP_FAILED))
+ return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT;
+
+ postmap:
+ _dl_postprocess_loadcmd (l, header, c);
+
+ if (c->allocend > c->dataend)
+ {
+ /* Extra zero pages should appear at the end of this segment,
+ after the data mapped from the file. */
+ ElfW(Addr) zero, zeroend, zeropage;
+
+ zero = l->l_addr + c->dataend;
+ zeroend = l->l_addr + c->allocend;
+ zeropage = ((zero + GLRO(dl_pagesize) - 1)
+ & ~(GLRO(dl_pagesize) - 1));
+
+ if (zeroend < zeropage)
+ /* All the extra data is in the last page of the segment.
+ We can just zero it. */
+ zeropage = zeroend;
+
+ if (zeropage > zero)
+ {
+ /* Zero the final part of the last page of the segment. */
+ if (__glibc_unlikely ((c->prot & PROT_WRITE) == 0))
+ {
+ /* Dag nab it. */
+ if (__mprotect ((caddr_t) (zero
+ & ~(GLRO(dl_pagesize) - 1)),
+ GLRO(dl_pagesize), c->prot|PROT_WRITE) < 0)
+ return DL_MAP_SEGMENTS_ERROR_MPROTECT;
+ }
+ memset ((void *) zero, '\0', zeropage - zero);
+ if (__glibc_unlikely ((c->prot & PROT_WRITE) == 0))
+ __mprotect ((caddr_t) (zero & ~(GLRO(dl_pagesize) - 1)),
+ GLRO(dl_pagesize), c->prot);
+ }
+
+ if (zeroend > zeropage)
+ {
+ /* Map the remaining zero pages in from the zero fill FD. */
+ caddr_t mapat;
+ mapat = __mmap ((caddr_t) zeropage, zeroend - zeropage,
+ c->prot, MAP_ANON|MAP_PRIVATE|MAP_FIXED,
+ -1, 0);
+ if (__glibc_unlikely (mapat == MAP_FAILED))
+ return DL_MAP_SEGMENTS_ERROR_MAP_ZERO_FILL;
+ }
+ }
+
+ ++c;
+ }
+
+ /* Notify ELF_PREFERRED_ADDRESS that we have to load this one
+ fixed. */
+ ELF_FIXED_ADDRESS (loader, c->mapstart);
+
+ return NULL;
+}