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authorFlorian Weimer <fweimer@redhat.com>2017-01-24 18:32:30 +0100
committerFlorian Weimer <fweimer@redhat.com>2017-01-24 18:32:30 +0100
commitdefaba407d488d348eb1849cc9b57d2269e5cf9d (patch)
tree02d6304fe6aaa3c144b302963b70a39eb3824afb
parentfeb6d6b394bd0ebd74d3f4370394dfb94b1f011a (diff)
downloadtermbaud-fw/bug21041.tar.gz
termbaud-fw/bug21041.tar.xz
termbaud-fw/bug21041.zip
WIP delayed IFUNC relocationfw/bug21041
-rw-r--r--elf/Makefile2
-rw-r--r--elf/dl-ifunc.c192
-rw-r--r--elf/dl-ifunc.h88
-rw-r--r--elf/dl-open.c4
-rw-r--r--elf/rtld.c6
-rw-r--r--include/link.h6
-rw-r--r--sysdeps/x86_64/dl-ifunc-reloc.h91
-rw-r--r--sysdeps/x86_64/dl-machine.h26
8 files changed, 393 insertions, 22 deletions
diff --git a/elf/Makefile b/elf/Makefile
index c7a29693bd4..04c00133809 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -29,7 +29,7 @@ routines = $(all-dl-routines) dl-support dl-iteratephdr \
# The core dynamic linking functions are in libc for the static and
# profiled libraries.
dl-routines = $(addprefix dl-,load lookup object reloc deps hwcaps \
- runtime init fini debug misc \
+ runtime init fini debug misc ifunc \
version profile conflict tls origin scope \
execstack caller open close trampoline)
ifeq (yes,$(use-ldconfig))
diff --git a/elf/dl-ifunc.c b/elf/dl-ifunc.c
new file mode 100644
index 00000000000..96e4d077d81
--- /dev/null
+++ b/elf/dl-ifunc.c
@@ -0,0 +1,192 @@
+/* Delayed IFUNC processing.
+ Copyright (C) 2017 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/>. */
+
+#ifdef HAVE_IFUNC
+
+# include <dl-ifunc.h>
+# include <errno.h>
+# include <ldsodefs.h>
+# include <sys/mman.h>
+# include <unistd.h>
+
+/* Machine-specific definitions. */
+# include <dl-ifunc-reloc.h>
+
+/* This struct covers a whole page containing individual struct
+ dl_ifunc_relocation elements, which are allocated individually by
+ allocate_relocation below. */
+struct dl_ifunc_relocation_array
+{
+ struct dl_ifunc_relocation_array *next;
+ struct dl_ifunc_relocation data[];
+};
+
+/* Global list of allocated arrays of struct dl_ifunc_relocation
+ elements. */
+static struct dl_ifunc_relocation_array *array_list;
+
+/* Position of the next allocation in the current array used as the
+ source of struct dl_ifunc_relocation allocations. */
+static struct dl_ifunc_relocation *next_alloc;
+static unsigned int remaining_alloc;
+
+/* Allocate a new struct dl_ifunc_relocation_array object. Return the
+ first data object therein. Update array_list, next_alloc,
+ remaining_alloc. This function assumes taht remaining_alloc is
+ zero. */
+static struct dl_ifunc_relocation *
+allocate_array (void)
+{
+ size_t page_size = GLRO(dl_pagesize);
+ void *ptr = __mmap (NULL, page_size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (ptr == MAP_FAILED)
+ _dl_signal_error (ENOMEM, NULL, NULL,
+ "cannot allocate IFUNC resolver information");
+ struct dl_ifunc_relocation_array *new_head = ptr;
+ new_head->next = array_list;
+ array_list = new_head;
+ next_alloc = &new_head->data[1];
+ /* The function returns the first element of the new array. */
+ remaining_alloc
+ = (page_size - offsetof (struct dl_ifunc_relocation_array, data))
+ / sizeof (new_head->data[0]) - 1;
+ return &new_head->data[0];
+}
+
+/* Allocate whone struct dl_ifunc_relocation element from the active
+ array. Updated next_alloc, remaining_alloc, and potentially
+ array_list. */
+static struct dl_ifunc_relocation *
+allocate_ifunc (void)
+{
+ if (remaining_alloc == 0)
+ return allocate_array ();
+ --remaining_alloc;
+ return next_alloc++;
+}
+
+/* Deallocate the list of array allocations starting at
+ array_list. */
+static void
+free_allocations (void)
+{
+ size_t page_size = GLRO(dl_pagesize);
+ struct dl_ifunc_relocation_array *p = array_list;
+ while (p != NULL)
+ {
+ struct dl_ifunc_relocation_array *next = p->next;
+ munmap (p, page_size);
+ p = next;
+ }
+ /* Restart from scratch if _dl_ifunc_record_reloc is called
+ again. */
+ array_list = NULL;
+ next_alloc = NULL;
+ remaining_alloc = 0;
+}
+
+/* Process all delayed IFUNC resolutions for IFUNC_MAP alone. */
+static void
+apply_relocations (struct link_map *ifunc_map)
+{
+ if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS)
+ && ifunc_map->l_name != NULL)
+ _dl_debug_printf ("applying delayed IFUNC relocations against %s\n",
+ ifunc_map->l_name);
+
+ struct dl_ifunc_relocation *p = ifunc_map->l_ifunc_relocations;
+ unsigned int count = 0;
+ while (p != NULL)
+ {
+ if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS)
+ && ifunc_map->l_name != NULL)
+ {
+ if (p->ifunc_sym == NULL)
+ _dl_debug_printf ("processing relative IFUNC relocation for %s\n",
+ ifunc_map->l_name);
+ else
+ {
+ const char *strtab = (const char *) D_PTR (ifunc_map, l_info[DT_STRTAB]);
+ _dl_debug_printf ("binding IFUNC symbol %s in %s against %s\n",
+ strtab + p->ifunc_sym->st_name,
+ p->reloc_map->l_name, ifunc_map->l_name);
+ }
+ }
+ _dl_ifunc_process_relocation (p, ifunc_map);
+ p = p->next;
+ ++count;
+ }
+
+ if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS)
+ && ifunc_map->l_name != NULL)
+ _dl_debug_printf ("%u delayed IFUNC relocations performed against %s\n",
+ count, ifunc_map->l_name);
+
+ /* No deallocation takes place here. All allocated objects are
+ freed in bulk by a later call to free_allocations. */
+ ifunc_map->l_ifunc_relocations = NULL;
+}
+
+void internal_function
+_dl_ifunc_record_reloc (struct link_map *reloc_map,
+ const ElfW(Rela) *reloc,
+ ElfW(Addr) *reloc_addr,
+ struct link_map *ifunc_map,
+ const ElfW(Sym) *ifunc_sym)
+{
+ /* Add the delayed IFUNC relocation to the list for ifunc_map. */
+ struct dl_ifunc_relocation *ifunc = allocate_ifunc ();
+ *ifunc = (struct dl_ifunc_relocation)
+ {
+ .reloc_map = reloc_map,
+ .reloc = reloc,
+ .reloc_addr = reloc_addr,
+ .ifunc_sym = ifunc_sym,
+ .next = ifunc_map->l_ifunc_relocations,
+ };
+ ifunc_map->l_ifunc_relocations = ifunc;
+}
+
+void internal_function
+_dl_ifunc_apply_relocations (struct link_map *new)
+{
+ /* Traverse the search list in reverse order, in case an IFUNC
+ resolver calls into one its dependencies, and those dependency
+ needs IFUNC resolution as well. */
+ struct link_map **r_list = new->l_searchlist.r_list;
+ for (unsigned int i = new->l_searchlist.r_nlist; i-- > 0; )
+ {
+ struct link_map *l = r_list[i];
+ if (l->l_ifunc_relocations != NULL)
+ apply_relocations (l);
+ }
+ free_allocations ();
+}
+
+void internal_function
+_dl_ifunc_clear_relocations (struct link_map *map)
+{
+ Lmid_t nsid = map->l_ns;
+ struct link_namespaces *ns = &GL(dl_ns)[nsid];
+ for (struct link_map *l = ns->_ns_loaded; l != NULL; l = l->l_next)
+ l->l_ifunc_relocations = NULL;
+ free_allocations ();
+}
+
+#endif /* HAVE_IFUNC */
diff --git a/elf/dl-ifunc.h b/elf/dl-ifunc.h
new file mode 100644
index 00000000000..39a5c12c73f
--- /dev/null
+++ b/elf/dl-ifunc.h
@@ -0,0 +1,88 @@
+/* Private declarations for delayed IFUNC processing.
+ Copyright (C) 2017 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/>. */
+
+#ifndef DL_IFUNC_H
+#define DL_IFUNC_H
+
+#include <link.h>
+
+/* All functions declared in this file must be called while the global
+ rtld lock is acquired. */
+
+/* Apply all pending IFUNC relocations in the search scope of the new
+ link map. Deallocate all auxiliary allocations. */
+void _dl_ifunc_apply_relocations (struct link_map *new)
+ attribute_hidden internal_function;
+
+/* Clear all allocated delayed IFUNC relocations in the namespace of
+ the link map. Deallocate all auxiliary allocations. This function
+ is intended for clearing up after a dlopen failure. */
+void _dl_ifunc_clear_relocations (struct link_map *map)
+ attribute_hidden internal_function;
+
+/* The no-op implementatoin is only available if IFUNCs are
+ supported. */
+#ifdef HAVE_IFUNC
+
+/* Delayed IFUNC relocation. For each link map with a referenced
+ IFUNC symbol, a separate single-linked list of delayed IFUNC
+ relocations exists while the dynamic linker is running. */
+struct dl_ifunc_relocation
+{
+ /* Information about the relocation. */
+ struct link_map *reloc_map;
+ const ElfW(Rela) *reloc;
+ ElfW(Addr) *reloc_addr;
+
+ /* Information about the IFUNC resolver. The corresponding symbol
+ map is implied. */
+ const ElfW(Sym) *ifunc_sym;
+
+ /* Pointer to the next element in the list of IFUNC relocations for
+ the symbol map. */
+ struct dl_ifunc_relocation *next;
+};
+
+/* Record a delayed IFUNC relocation for IFUNC_SYM at *RELOC_ADDR.
+ The relocation is associated with IFUNC_MAP. Can raise an error
+ using _dl_signal_error. IFUNC_SYM can be NULL if the relocation is
+ a relative IFUNC relocation. */
+void _dl_ifunc_record_reloc (struct link_map *reloc_map,
+ const ElfW(Rela) *reloc,
+ ElfW(Addr) *reloc_addr,
+ struct link_map *ifunc_map,
+ const ElfW(Sym) *ifunc_sym)
+ attribute_hidden internal_function;
+
+#else /* !HAVE_IFUNC */
+
+/* Dummy implementations for targets without IFUNC support. */
+
+static inline void
+_dl_ifunc_apply_relocations (struct link_map *new)
+{
+}
+
+static inline void
+_dl_ifunc_clear_relocations (struct link_map *map)
+{
+}
+
+#endif /* !HAVE_IFUNC */
+
+#endif /* DL_IFUNC_H */
diff --git a/elf/dl-open.c b/elf/dl-open.c
index d238fb2cc52..e40fb3b7e8f 100644
--- a/elf/dl-open.c
+++ b/elf/dl-open.c
@@ -35,7 +35,7 @@
#include <atomic.h>
#include <dl-dst.h>
-
+#include <dl-ifunc.h>
extern int __libc_multiple_libcs; /* Defined in init-first.c. */
@@ -552,6 +552,7 @@ TLS generation counter wrapped! Please report this."));
}
}
+ _dl_ifunc_apply_relocations (new);
_dl_relocate_apply_relro (new);
/* Notify the debugger all new objects have been relocated. */
@@ -673,6 +674,7 @@ no more namespaces available for dlmopen()"));
if ((mode & __RTLD_AUDIT) == 0)
GL(dl_tls_dtv_gaps) = true;
+ _dl_ifunc_clear_relocations (args.map);
_dl_close_worker (args.map, true);
}
diff --git a/elf/rtld.c b/elf/rtld.c
index 16119e8c315..cb9d330d664 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -41,6 +41,7 @@
#include <tls.h>
#include <stap-probe.h>
#include <stackinfo.h>
+#include <dl-ifunc.h>
#include <assert.h>
@@ -2114,10 +2115,11 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n",
HP_TIMING_ACCUM_NT (relocate_time, add);
}
- /* Activate RELRO protection. In the prelink case, this was already
- done earlier. */
+ /* Perform delayed IFUNC relocations and activate RELRO protection.
+ In the prelink case, this was already done earlier. */
if (! prelinked)
{
+ _dl_ifunc_apply_relocations (main_map);
/* Make sure that this covers the dynamic linker as well.
TODO: rtld_multiple_ref is always true because libc.so needs
the dynamic linker internally. */
diff --git a/include/link.h b/include/link.h
index eeb5f4d53b4..a8d85c9f370 100644
--- a/include/link.h
+++ b/include/link.h
@@ -60,6 +60,7 @@ struct r_search_path_elem;
/* Forward declaration. */
struct link_map;
+struct dl_ifunc_relocation;
/* Structure to describe a single list of scope elements. The lookup
functions get passed an array of pointers to such structures. */
@@ -318,6 +319,11 @@ struct link_map
ElfW(Addr) l_relro_addr;
size_t l_relro_size;
+#ifdef HAVE_IFUNC
+ /* Deferred IFUNC relocations. Only used during relocation. */
+ struct dl_ifunc_relocation *l_ifunc_relocations;
+#endif
+
unsigned long long int l_serial;
/* Audit information. This array apparent must be the last in the
diff --git a/sysdeps/x86_64/dl-ifunc-reloc.h b/sysdeps/x86_64/dl-ifunc-reloc.h
new file mode 100644
index 00000000000..bf436bf71c7
--- /dev/null
+++ b/sysdeps/x86_64/dl-ifunc-reloc.h
@@ -0,0 +1,91 @@
+/* IFUNC relocation processing, x86-64 version.
+ Copyright (C) 2001-2017 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Andreas Jaeger <aj@suse.de>.
+
+ 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/>. */
+
+#ifndef DL_IFUNC_RELOC_H
+#define DL_IFUNC_RELOC_H
+
+static inline void
+_dl_ifunc_process_relocation (const struct dl_ifunc_relocation *ifunc,
+ struct link_map *sym_map)
+{
+ const ElfW(Rela) *reloc = ifunc->reloc;
+ const unsigned long int r_type = ELFW(R_TYPE) (reloc->r_info);
+ ElfW(Addr) *const reloc_addr = ifunc->reloc_addr;
+
+ /* Special case: A relative IFUNC relocation does not have an
+ associated symbol. */
+ if (r_type == R_X86_64_IRELATIVE)
+ {
+ ElfW(Addr) value = sym_map->l_addr + reloc->r_addend;
+ value = ((ElfW(Addr) (*) (void)) value) ();
+ *reloc_addr = value;
+ return;
+ }
+
+ ElfW(Addr) value = (ElfW(Addr)) sym_map->l_addr + ifunc->ifunc_sym->st_value;
+ value = ((ElfW(Addr) (*) (void)) value) ();
+
+ /* This switch statement needs to be kept in sync with the switch
+ statement in elf_machine_rela. */
+ switch (r_type)
+ {
+ case R_X86_64_GLOB_DAT:
+ case R_X86_64_JUMP_SLOT:
+ *reloc_addr = value + reloc->r_addend;
+ break;
+
+ case R_X86_64_64:
+ /* value + r_addend may be > 0xffffffff and R_X86_64_64
+ relocation updates the whole 64-bit entry. */
+ *(Elf64_Addr *) reloc_addr = (Elf64_Addr) value + reloc->r_addend;
+ break;
+ case R_X86_64_32:
+ value += reloc->r_addend;
+ *(unsigned int *) reloc_addr = value;
+
+ const char *fmt;
+ if (__glibc_unlikely (value > UINT_MAX))
+ {
+ const char *strtab;
+
+ fmt = "\
+%s: Symbol `%s' causes overflow in R_X86_64_32 relocation\n";
+ print_err:
+ strtab = (const char *) D_PTR (sym_map, l_info[DT_STRTAB]);
+
+ _dl_error_printf (fmt, RTLD_PROGNAME,
+ strtab + ifunc->ifunc_sym->st_name);
+ }
+ break;
+ case R_X86_64_PC32:
+ value += reloc->r_addend - (ElfW(Addr)) reloc_addr;
+ *(unsigned int *) reloc_addr = value;
+ if (__glibc_unlikely (value != (int) value))
+ {
+ fmt = "\
+%s: Symbol `%s' causes overflow in R_X86_64_PC32 relocation\n";
+ goto print_err;
+ }
+ break;
+ default:
+ _dl_reloc_bad_type (ifunc->reloc_map, r_type, 0);
+ }
+}
+
+#endif /* DL_IFUNC_RELOC_H */
diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
index 3e7ae22c67a..02b6703b2ea 100644
--- a/sysdeps/x86_64/dl-machine.h
+++ b/sysdeps/x86_64/dl-machine.h
@@ -27,6 +27,7 @@
#include <tls.h>
#include <dl-tlsdesc.h>
#include <cpu-features.c>
+#include <dl-ifunc.h>
/* Return nonzero iff ELF header is compatible with the running host. */
static inline int __attribute__ ((unused))
@@ -326,29 +327,20 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
ElfW(Addr) value = (sym == NULL ? 0
: (ElfW(Addr)) sym_map->l_addr + sym->st_value);
+# ifndef RTLD_BOOTSTRAP
if (sym != NULL
&& __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC,
0)
&& __builtin_expect (sym->st_shndx != SHN_UNDEF, 1)
&& __builtin_expect (!skip_ifunc, 1))
{
-# ifndef RTLD_BOOTSTRAP
- if (sym_map != map
- && sym_map->l_type != lt_executable
- && !sym_map->l_relocated)
- {
- const char *strtab
- = (const char *) D_PTR (map, l_info[DT_STRTAB]);
- _dl_fatal_printf ("\
-%s: Relink `%s' with `%s' for IFUNC symbol `%s'\n",
- RTLD_PROGNAME, map->l_name,
- sym_map->l_name,
- strtab + refsym->st_name);
- }
-# endif
- value = ((ElfW(Addr) (*) (void)) value) ();
+ _dl_ifunc_record_reloc (map, reloc, reloc_addr, sym_map, sym);
+ return;
}
+# endif /* !RTLD_BOOTSTRAP */
+ /* This switch statement needs to be kept in sync with the
+ switch statement in _dl_ifunc_process_relocation. */
switch (r_type)
{
# ifndef RTLD_BOOTSTRAP
@@ -528,9 +520,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
break;
# endif
case R_X86_64_IRELATIVE:
- value = map->l_addr + reloc->r_addend;
- value = ((ElfW(Addr) (*) (void)) value) ();
- *reloc_addr = value;
+ _dl_ifunc_record_reloc (map, reloc, reloc_addr, map, NULL);
break;
default:
_dl_reloc_bad_type (map, r_type, 0);