This is needed to support debugging dlopened shared libraries in static
PIE.
[BZ #23206]
* elf/dl-reloc-static-pie.c (_dl_relocate_static_pie): Initialize
_r_debug and update DT_DEBUG for debugger.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
alloca for it may cause stack overflow. If the note is larger than
__MAX_ALLOCA_CUTOFF, use dynamically allocated memory to read it in.
2018-05-05 Paul Pluzhnikov <ppluzhnikov@google.com>
[BZ #20419]
* elf/dl-load.c (open_verify): Fix stack overflow.
* elf/Makefile (tst-big-note): New test.
* elf/tst-big-note-lib.S: New.
* elf/tst-big-note.c: New.
Do not relocate absolute symbols by the base address. Such symbols have
SHN_ABS as the section index and their value is not supposed to be
affected by relocation as per the ELF gABI[1]:
"SHN_ABS
The symbol has an absolute value that will not change because of
relocation."
The reason for our non-conformance here seems to be an old SysV linker
bug causing symbols like _DYNAMIC to be incorrectly emitted as absolute
symbols[2]. However in a previous discussion it was pointed that this
is seriously flawed by preventing the lone purpose of the existence of
absolute symbols from being used[3]:
"On the contrary, the only interpretation that makes sense to me is that
it will not change because of relocation at link time or at load time.
Absolute symbols, from the days of the earliest linking loaders, have
been used to represent addresses that are outside the address space of
the module (e.g., memory-mapped addresses or kernel gateway pages).
They've even been used to represent true symbolic constants (e.g.,
system entry point numbers, sizes, version numbers). There's no other
way to represent a true absolute symbol, while the meaning you seek is
easily represented by giving the symbol a non-negative st_shndx value."
and we ought to stop supporting our current broken interpretation.
Update processing for dladdr(3) and dladdr1(3) so that SHN_ABS symbols
are ignored, because under the corrected interpretation they do not
represent addresses within a mapped file and therefore are not supposed
to be considered.
References:
[1] "System V Application Binary Interface - DRAFT - 19 October 2010",
The SCO Group, Section "Symbol Table",
<http://www.sco.com/developers/gabi/2012-12-31/ch4.symtab.html>
[2] Alan Modra, "Absolute symbols"
<https://sourceware.org/ml/binutils/2012-05/msg00019.html>
[3] Cary Coutant, "Re: Absolute symbols"
<https://sourceware.org/ml/binutils/2012-05/msg00020.html>
[BZ #19818]
* sysdeps/generic/ldsodefs.h (SYMBOL_ADDRESS): Handle SHN_ABS
symbols.
* elf/dl-addr.c (determine_info): Ignore SHN_ABS symbols.
* elf/tst-absolute-sym.c: New file.
* elf/tst-absolute-sym-lib.c: New file.
* elf/tst-absolute-sym-lib.lds: New file.
* elf/Makefile (tests): Add `tst-absolute-sym'.
(modules-names): Add `tst-absolute-sym-lib'.
(LDLIBS-tst-absolute-sym-lib.so): New variable.
($(objpfx)tst-absolute-sym-lib.so): New dependency.
($(objpfx)tst-absolute-sym): New dependency.
Wrap symbol address run-time calculation into a macro and use it
throughout, replacing inline calculations.
There are a couple of variants, most of them different in a functionally
insignificant way. Most calculations are right following RESOLVE_MAP,
at which point either the map or the symbol returned can be checked for
validity as the macro sets either both or neither. In some places both
the symbol and the map has to be checked however.
My initial implementation therefore always checked both, however that
resulted in code larger by as much as 0.3%, as many places know from
elsewhere that no check is needed. I have decided the size growth was
unacceptable.
Having looked closer I realized that it's the map that is the culprit.
Therefore I have modified LOOKUP_VALUE_ADDRESS to accept an additional
boolean argument telling it to access the map without checking it for
validity. This in turn has brought quite nice results, with new code
actually being smaller for i686, and MIPS o32, n32 and little-endian n64
targets, unchanged in size for x86-64 and, unusually, marginally larger
for big-endian MIPS n64, as follows:
i686:
text data bss dec hex filename
152255 4052 192 156499 26353 ld-2.27.9000-base.so
152159 4052 192 156403 262f3 ld-2.27.9000-elf-symbol-value.so
MIPS/o32/el:
text data bss dec hex filename
142906 4396 260 147562 2406a ld-2.27.9000-base.so
142890 4396 260 147546 2405a ld-2.27.9000-elf-symbol-value.so
MIPS/n32/el:
text data bss dec hex filename
142267 4404 260 146931 23df3 ld-2.27.9000-base.so
142171 4404 260 146835 23d93 ld-2.27.9000-elf-symbol-value.so
MIPS/n64/el:
text data bss dec hex filename
149835 7376 408 157619 267b3 ld-2.27.9000-base.so
149787 7376 408 157571 26783 ld-2.27.9000-elf-symbol-value.so
MIPS/o32/eb:
text data bss dec hex filename
142870 4396 260 147526 24046 ld-2.27.9000-base.so
142854 4396 260 147510 24036 ld-2.27.9000-elf-symbol-value.so
MIPS/n32/eb:
text data bss dec hex filename
142019 4404 260 146683 23cfb ld-2.27.9000-base.so
141923 4404 260 146587 23c9b ld-2.27.9000-elf-symbol-value.so
MIPS/n64/eb:
text data bss dec hex filename
149763 7376 408 157547 2676b ld-2.27.9000-base.so
149779 7376 408 157563 2677b ld-2.27.9000-elf-symbol-value.so
x86-64:
text data bss dec hex filename
148462 6452 400 155314 25eb2 ld-2.27.9000-base.so
148462 6452 400 155314 25eb2 ld-2.27.9000-elf-symbol-value.so
[BZ #19818]
* sysdeps/generic/ldsodefs.h (LOOKUP_VALUE_ADDRESS): Add `set'
parameter.
(SYMBOL_ADDRESS): New macro.
[!ELF_FUNCTION_PTR_IS_SPECIAL] (DL_SYMBOL_ADDRESS): Use
SYMBOL_ADDRESS for symbol address calculation.
* elf/dl-runtime.c (_dl_fixup): Likewise.
(_dl_profile_fixup): Likewise.
* elf/dl-symaddr.c (_dl_symbol_address): Likewise.
* elf/rtld.c (dl_main): Likewise.
* sysdeps/aarch64/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/alpha/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/arm/dl-machine.h (elf_machine_rel): Likewise.
(elf_machine_rela): Likewise.
* sysdeps/hppa/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/hppa/dl-symaddr.c (_dl_symbol_address): Likewise.
* sysdeps/i386/dl-machine.h (elf_machine_rel): Likewise.
(elf_machine_rela): Likewise.
* sysdeps/ia64/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/m68k/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/microblaze/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/mips/dl-machine.h (ELF_MACHINE_BEFORE_RTLD_RELOC):
Likewise.
(elf_machine_reloc): Likewise.
(elf_machine_got_rel): Likewise.
* sysdeps/mips/dl-trampoline.c (__dl_runtime_resolve): Likewise.
* sysdeps/nios2/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/powerpc/powerpc32/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/powerpc/powerpc64/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/riscv/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/s390/s390-32/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/s390/s390-64/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/sh/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/sparc/sparc32/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/sparc/sparc64/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/tile/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/x86_64/dl-machine.h (elf_machine_rela): Likewise.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
When $(tests-execstack-$(have-z-execstack)) is added to tests before
it is defined, it is empty. This patch adds it to tests after it is
defined.
[BZ #22998]
* elf/Makefile (tests): Add $(tests-execstack-$(have-z-execstack))
after it is defined.
As requested in bug 20079, this patch adds SHT_X86_64_UNWIND (a
standard value from the x86_64 ABI) to elf.h.
Tested for x86_64.
[BZ #20079]
* elf/elf.h (SHT_X86_64_UNWIND): New macro.
If the system crashes before the file data has been written to disk, the
file system recovery upon the next mount may restore a partially
rewritten temporary file under the non-temporary (final) name (after the
rename operation).
This looks like a post-exploitation hardening measure: If an attacker is
able to redirect execution flow, they could use that to load a DSO which
contains additional code (or perhaps make the stack executable).
However, the checks are not in the correct place to be effective: If
they are performed before the critical operation, an attacker with
sufficient control over execution flow could simply jump directly to
the code which performs the operation, bypassing the check. The check
would have to be executed unconditionally after the operation and
terminate the process in case a caller violation was detected.
Furthermore, in _dl_check_caller, there was a fallback reading global
writable data (GL(dl_rtld_map).l_map_start and
GL(dl_rtld_map).l_text_end), which could conceivably be targeted by an
attacker to disable the check, too.
Other critical functions (such as system) remain completely
unprotected, so the value of these additional checks does not appear
that large. Therefore this commit removes this functionality.
Linux 4.15 adds NT_S390_RI_CB to linux/elf.h (and NT_ARM_SVE, which we
already have in glibc). This shows up that various other ELF note
values from linux/elf.h are missing from glibc's elf.h.
This patch adds the missing values that are relevant to glibc
architectures. As elf.h is a general description of the ELF format,
not necessarily limited to glibc configurations, there's an argument
for having the remaining NT_* values that Linux uses for non-glibc
architectures in glibc's elf.h as well, but this patch does not add
them.
Adding the NT_PRFPREG name is bug 14890. That bug also requests
making the NT_FPREGSET name obsolete. Given that elf.h is not just
for Linux but can describe ELF for other operating systems, I don't
think that a change of name in the Linux kernel is sufficient
justification for declaring the other name obsolete; there can be
multiple names for the same note value, even with incompatible
semantics, if those reflect variants of the ELF format in actual use.
For example, FreeBSD appears still to have the name NT_FPREGSET
<https://github.com/freebsd/freebsd/blob/master/sys/sys/elf_common.h>
(note: I haven't checked whether the FreeBSD kernel actually generates
such notes or whether this is actually an other-OS definition present
in FreeBSD's header).
[BZ #14890]
* elf/elf.h (NT_PRFPREG): New macro.
(NT_S390_VXRS_LOW): Likewise.
(NT_S390_VXRS_HIGH): Likewise.
(NT_S390_GS_CB): Likewise.
(NT_S390_GS_BC): Likewise.
(NT_S390_RI_CB): Likewise.
The only differences in ld.so are line numbers for asserts.
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
* elf/dl-addr.c (determine_info): Use ADDRIDX with DT_GNU_HASH.
* elf/dl-lookup.c (_dl_setup_hash): Likewise.
* elf/get-dynamic-info.h (elf_get_dynamic_info): Likewise.
The RISC-V port defines ELF flags that enforce compatibility between
various objects. This adds the shared support necessary for these
flags.
2018-01-25 Palmer Dabbelt <palmer@sifive.com>
* elf/cache.c (print_entry): Add FLAG_RISCV_FLOAT_ABI_SOFT and
FLAG_RISCV_FLOAT_ABI_DOUBLE.
* elf/elf.h (EF_RISCV_RVC): New define.
(EF_RISCV_FLOAT_ABI): Likewise.
(EF_RISCV_FLOAT_ABI_SOFT): Likewise.
(EF_RISCV_FLOAT_ABI_SINGLE): Likewise.
(EF_RISCV_FLOAT_ABI_DOUBLE): Likewise.
(EF_RISCV_FLOAT_ABI_QUAD): Likewise.
* sysdeps/generic/ldconfig.h (FLAG_RISCV_FLOAT_ABI_SOFT): New
define.
(FLAG_RISCV_FLOAT_ABI_DOUBLE): Likewise.
This patch synchronizes DF_1_* flags with binutils
and ensures that all DF_1_* flags defined in binutil's
include/elf/common.h are also defined glibc's elf/elf.h.
This is a user visible change since elf/elf.h is installed
by default as /usr/include/elf.h.
Signed-off-by: Carlos O'Donell <carlos@redhat.com>
This commit adds a new _dl_open_hook entry for dlvsym and implements the
function using the existing dl_lookup_symbol_x function supplied by the
dynamic loader.
A new hook variable, _dl_open_hook2, is introduced, which should make
this change suitable for backporting: For old statically linked
binaries, __libc_dlvsym will always return NULL.
The fillin_rpath function in elf/dl-load.c loops over each RPATH or
RUNPATH tokens and interprets empty tokens as the current directory
("./"). In practice the check for empty token is done *after* the
dynamic string token expansion. The expansion process can return an
empty string for the $ORIGIN token if __libc_enable_secure is set
or if the path of the binary can not be determined (/proc not mounted).
Fix that by moving the check for empty tokens before the dynamic string
token expansion. In addition, check for NULL pointer or empty strings
return by expand_dynamic_string_token.
The above changes highlighted a bug in decompose_rpath, an empty array
is represented by the first element being NULL at the fillin_rpath
level, but by using a -1 pointer in decompose_rpath and other functions.
Changelog:
[BZ #22625]
* elf/dl-load.c (fillin_rpath): Check for empty tokens before dynamic
string token expansion. Check for NULL pointer or empty string possibly
returned by expand_dynamic_string_token.
(decompose_rpath): Check for empty path after dynamic string
token expansion.
is_path argument is no longer used and could be safely removed.
* elf/dl-dst.h (DL_DST_COUNT): Remove is_path argument, all callers
updated.
* elf/dl-load.c (is_dst, _dl_dst_count, _dl_dst_substitute,
expand_dynamic_string_token): Likewise.
* sysdeps/generic/ldsodefs.h (_dl_dst_count, _dl_dst_substitute): Remove
is_path argument.
is_dst is called either by _dl_dst_count or by _dl_dst_substitute.
_dl_dst_count is called by DL_DST_COUNT only.
DL_DST_COUNT is called either by expand_dst with is_path == 0
or by expand_dynamic_string_token.
_dl_dst_substitute is called either from expand_dst with is_path == 0
or from expand_dynamic_string_token.
The latter function is called either from _dl_map_object with is_path == 0
or from fillin_rpath with is_path == 1 and name containing no ':'.
In any case (is_path && name[i] == ':') is always false and all code
depending on it can be safely removed.
* elf/dl-load.c (is_dst): Remove checks that is_path is set and name
contains ':', and all code depending on these checks.
There are just two users of _dl_dst_substitute: one is expand_dst that
sets is_path argument to 0, another one is expand_dynamic_string_token.
The latter function also has just two users: one is _dl_map_object that
sets is_path argument to 0, another one is fillin_rpath that sets
is_path argument to 1 and name argument contains no ':'.
In any case (is_path && name[i] == ':') is always false and all code
depending on it can be safely removed.
* elf/dl-load.c (_dl_dst_substitute): Remove checks that is_path
is set and name contains ':', and all code depending on these checks.
There are just two users of fillin_rpath: one is decompose_rpath that
sets check_trusted argument to 0, another one is _dl_init_paths that
sets check_trusted argument to __libc_enable_secure and invokes
fillin_rpath only when LD_LIBRARY_PATH is non-empty.
Starting with commit
glibc-2.25.90-512-gf6110a8fee2ca36f8e2d2abecf3cba9fa7b8ea7d,
LD_LIBRARY_PATH is ignored for __libc_enable_secure executables,
so check_trusted argument of fillin_rpath is always zero.
* elf/dl-load.c (is_trusted_path): Remove.
(fillin_rpath): Remove check_trusted argument and its use,
all callers changed.
After
commit 9d7a3741c9
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Fri Dec 15 16:59:33 2017 -0800
Add --enable-static-pie configure option to build static PIE [BZ #19574]
and
commit 00c714df39
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Mon Dec 18 12:24:26 2017 -0800
Pass -no-pie to GCC only if GCC defaults to PIE [BZ #22614]
$(no-pie-ldflag) is no longer effective since no-pie-ldflag is defined
to -no-pie only if GCC defaults to PIE. When --enable-static-pie is
used to configure glibc build and GCC doesn't default to PIE. no-pie-ldflag
is undefined and these tests:
elf/Makefile:LDFLAGS-tst-dlopen-aout = $(no-pie-ldflag)
elf/Makefile:LDFLAGS-tst-prelink = $(no-pie-ldflag)
elf/Makefile:LDFLAGS-tst-main1 = $(no-pie-ldflag)
gmon/Makefile:LDFLAGS-tst-gmon := $(no-pie-ldflag)
may fail to link. This patch replaces "-pie" with
$(if $($(@F)-no-pie),$(no-pie-ldflag),-pie)
and repleces
LDFLAGS-* = $(no-pie-ldflag)
with
tst-*-no-pie = yes
so that tst-dlopen-aout, tst-prelink, tst-main1 and tst-gmon are always
built as non-PIE, with and without --enable-static-pie, regardless if
GCC defaults to PIE or non-PIE.
Tested with build-many-glibcs.py without --enable-static-pie as well as
with --enable-static-pie for x86_64, x32 and i686.
[BZ #22630]
* Makeconfig (link-pie-before-libc): Replace -pie with
$(if $($(@F)-no-pie),$(no-pie-ldflag),-pie).
* elf/Makefile (LDFLAGS-tst-dlopen-aout): Removed.
(tst-dlopen-aout-no-pie): New.
(LDFLAGS-tst-prelink): Removed.
(tst-prelink-no-pie): New.
(LDFLAGS-tst-main1): Removed.
(tst-main1-no-pie): New.
* gmon/Makefile (LDFLAGS-tst-gmon): Removed.
(tst-gmon-no-pie): New.
GLRO (_rtld_global_ro) is read-only after initialization and can
therefore not be patched at run time, unlike the hook table addresses
and their contents, so this is a desirable hardening feature.
The hooks are only needed if ld.so has not been initialized, and this
happens only after static dlopen (dlmopen uses a single ld.so object
across all namespaces).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Starting with commit
glibc-2.18.90-470-g2a939a7e6d81f109d49306bc2e10b4ac9ceed8f9 that
introduced substitution of dynamic string tokens in fillin_rpath,
_dl_init_paths invokes _dl_dst_substitute for $LD_LIBRARY_PATH twice:
the first time it's called directly, the second time the result
is passed on to fillin_rpath which calls expand_dynamic_string_token
which in turn calls _dl_dst_substitute, leading to the following
behaviour:
$ mkdir -p /tmp/'$ORIGIN' && cd /tmp/'$ORIGIN' &&
echo 'int main(){}' |gcc -xc - &&
strace -qq -E LD_LIBRARY_PATH='$ORIGIN' -e /open ./a.out
open("/tmp//tmp/$ORIGIN/tls/x86_64/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/tmp//tmp/$ORIGIN/tls/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/tmp//tmp/$ORIGIN/x86_64/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/tmp//tmp/$ORIGIN/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
open("/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
Fix this by removing the direct _dl_dst_substitute invocation.
* elf/dl-load.c (_dl_init_paths): Remove _dl_dst_substitute preparatory
code and invocation.
ldconfig supports `include' directives and use the glob function to
process them. The glob function sort entries according to the LC_COLLATE
category. When using a standard "include /etc/ld.so.conf.d/*.conf" entry
in /etc/ld.so.conf, the order therefore depends on the locale used to
run ldconfig. A few examples of locale specific order that might be
disturbing in that context compared to the C locale:
- The cs_CZ and sk_SK locales sort the digits after the letters.
- The et_EE locale sorts the 'z' between 's' and 't'.
This patch fixes that by setting LC_COLLATE to C in order to process
files in deterministic order, independently of the locale used to launch
ldconfig.
NOTE: This should NOT be backported to older release branches.
Changelog:
[BZ #22505]
* elf/ldconfig.c (main): Call setlocale to force LC_COLLATE to C.
The test tst-leaks1 exercises calling dlopen with a $ORIGIN DST.
This results in a theoretical leak e.g.
Memory not freed:
-----------------
Address Size Caller
0x0000000001d766c0 0x21 at 0x7fb1bd8bf4ab
Or as seen via valgrind:
==27582== 33 bytes in 1 blocks are still reachable in loss record 1 of 1
==27582== at 0x4C2CB6B: malloc (vg_replace_malloc.c:299)
==27582== by 0x40124AA: _dl_get_origin (dl-origin.c:50)
==27582== by 0x4007DB9: expand_dynamic_string_token (dl-load.c:382)
==27582== by 0x400899C: _dl_map_object (dl-load.c:2160)
==27582== by 0x4013020: dl_open_worker (dl-open.c:224)
==27582== by 0x5166F9B: _dl_catch_exception (dl-error-skeleton.c:198)
==27582== by 0x4012BD9: _dl_open (dl-open.c:594)
==27582== by 0x4E39EF5: dlopen_doit (dlopen.c:66)
==27582== by 0x5166F9B: _dl_catch_exception (dl-error-skeleton.c:198)
==27582== by 0x516700E: _dl_catch_error (dl-error-skeleton.c:217)
==27582== by 0x4E3A514: _dlerror_run (dlerror.c:162)
==27582== by 0x4E39F70: dlopen@@GLIBC_2.2.5 (dlopen.c:87)
There is no real leak.
The calling link map (the executable's link map) has it's l_origin
expanded for future use as part of _dl_get_origin, and that results
in the main executable link map having a N-byte allocation for
l->l_origin that is never freed since the executable's link map is
just a part of the process.
To take this into account we do one dlopen with $ORIGIN before
calling mtrace to force the initialization of the executable link
map.
Signed-off-by: Carlos O'Donell <carlos@redhat.com>
Static PIE extends address space layout randomization to static
executables. It provides additional security hardening benefits at
the cost of some memory and performance.
Dynamic linker, ld.so, is a standalone program which can be loaded at
any address. This patch adds a configure option, --enable-static-pie,
to embed the part of ld.so in static executable to create static position
independent executable (static PIE). A static PIE is similar to static
executable, but can be loaded at any address without help from a dynamic
linker. When --enable-static-pie is used to configure glibc, libc.a is
built as PIE and all static executables, including tests, are built as
static PIE. The resulting libc.a can be used together with GCC 8 or
above to build static PIE with the compiler option, -static-pie. But
GCC 8 isn't required to build glibc with --enable-static-pie. Only GCC
with PIE support is needed. When an older GCC is used to build glibc
with --enable-static-pie, proper input files are passed to linker to
create static executables as static PIE, together with "-z text" to
prevent dynamic relocations in read-only segments, which are not allowed
in static PIE.
The following changes are made for static PIE:
1. Add a new function, _dl_relocate_static_pie, to:
a. Get the run-time load address.
b. Read the dynamic section.
c. Perform dynamic relocations.
Dynamic linker also performs these steps. But static PIE doesn't load
any shared objects.
2. Call _dl_relocate_static_pie at entrance of LIBC_START_MAIN in
libc.a. crt1.o, which is used to create dynamic and non-PIE static
executables, is updated to include a dummy _dl_relocate_static_pie.
rcrt1.o is added to create static PIE, which will link in the real
_dl_relocate_static_pie. grcrt1.o is also added to create static PIE
with -pg. GCC 8 has been updated to support rcrt1.o and grcrt1.o for
static PIE.
Static PIE can work on all architectures which support PIE, provided:
1. Target must support accessing of local functions without dynamic
relocations, which is needed in start.S to call __libc_start_main with
function addresses of __libc_csu_init, __libc_csu_fini and main. All
functions in static PIE are local functions. If PIE start.S can't reach
main () defined in a shared object, the code sequence:
pass address of local_main to __libc_start_main
...
local_main:
tail call to main via PLT
can be used.
2. start.S is updated to check PIC instead SHARED for PIC code path and
avoid dynamic relocation, when PIC is defined and SHARED isn't defined,
to support static PIE.
3. All assembly codes are updated check PIC instead SHARED for PIC code
path to avoid dynamic relocations in read-only sections.
4. All assembly codes are updated check SHARED instead PIC for static
symbol name.
5. elf_machine_load_address in dl-machine.h are updated to support static
PIE.
6. __brk works without TLS nor dynamic relocations in read-only section
so that it can be used by __libc_setup_tls to initializes TLS in static
PIE.
NB: When glibc is built with GCC defaulted to PIE, libc.a is compiled
with -fPIE, regardless if --enable-static-pie is used to configure glibc.
When glibc is configured with --enable-static-pie, libc.a is compiled
with -fPIE, regardless whether GCC defaults to PIE or not. The same
libc.a can be used to build both static executable and static PIE.
There is no need for separate PIE copy of libc.a.
On x86-64, the normal static sln:
text data bss dec hex filename
625425 8284 5456 639165 9c0bd elf/sln
the static PIE sln:
text data bss dec hex filename
657626 20636 5392 683654 a6e86 elf/sln
The code size is increased by 5% and the binary size is increased by 7%.
Linker requirements to build glibc with --enable-static-pie:
1. Linker supports --no-dynamic-linker to remove PT_INTERP segment from
static PIE.
2. Linker can create working static PIE. The x86-64 linker needs the
fix for
https://sourceware.org/bugzilla/show_bug.cgi?id=21782
The i386 linker needs to be able to convert "movl main@GOT(%ebx), %eax"
to "leal main@GOTOFF(%ebx), %eax" if main is defined locally.
Binutils 2.29 or above are OK for i686 and x86-64. But linker status for
other targets need to be verified.
3. Linker should resolve undefined weak symbols to 0 in static PIE:
https://sourceware.org/bugzilla/show_bug.cgi?id=22269
4. Many ELF backend linkers incorrectly check bfd_link_pic for TLS
relocations, which should check bfd_link_executable instead:
https://sourceware.org/bugzilla/show_bug.cgi?id=22263
Tested on aarch64, i686 and x86-64.
Using GCC 7 and binutils master branch, build-many-glibcs.py with
--enable-static-pie with all patches for static PIE applied have the
following build successes:
PASS: glibcs-aarch64_be-linux-gnu build
PASS: glibcs-aarch64-linux-gnu build
PASS: glibcs-armeb-linux-gnueabi-be8 build
PASS: glibcs-armeb-linux-gnueabi build
PASS: glibcs-armeb-linux-gnueabihf-be8 build
PASS: glibcs-armeb-linux-gnueabihf build
PASS: glibcs-arm-linux-gnueabi build
PASS: glibcs-arm-linux-gnueabihf build
PASS: glibcs-arm-linux-gnueabihf-v7a build
PASS: glibcs-arm-linux-gnueabihf-v7a-disable-multi-arch build
PASS: glibcs-m68k-linux-gnu build
PASS: glibcs-microblazeel-linux-gnu build
PASS: glibcs-microblaze-linux-gnu build
PASS: glibcs-mips64el-linux-gnu-n32 build
PASS: glibcs-mips64el-linux-gnu-n32-nan2008 build
PASS: glibcs-mips64el-linux-gnu-n32-nan2008-soft build
PASS: glibcs-mips64el-linux-gnu-n32-soft build
PASS: glibcs-mips64el-linux-gnu-n64 build
PASS: glibcs-mips64el-linux-gnu-n64-nan2008 build
PASS: glibcs-mips64el-linux-gnu-n64-nan2008-soft build
PASS: glibcs-mips64el-linux-gnu-n64-soft build
PASS: glibcs-mips64-linux-gnu-n32 build
PASS: glibcs-mips64-linux-gnu-n32-nan2008 build
PASS: glibcs-mips64-linux-gnu-n32-nan2008-soft build
PASS: glibcs-mips64-linux-gnu-n32-soft build
PASS: glibcs-mips64-linux-gnu-n64 build
PASS: glibcs-mips64-linux-gnu-n64-nan2008 build
PASS: glibcs-mips64-linux-gnu-n64-nan2008-soft build
PASS: glibcs-mips64-linux-gnu-n64-soft build
PASS: glibcs-mipsel-linux-gnu build
PASS: glibcs-mipsel-linux-gnu-nan2008 build
PASS: glibcs-mipsel-linux-gnu-nan2008-soft build
PASS: glibcs-mipsel-linux-gnu-soft build
PASS: glibcs-mips-linux-gnu build
PASS: glibcs-mips-linux-gnu-nan2008 build
PASS: glibcs-mips-linux-gnu-nan2008-soft build
PASS: glibcs-mips-linux-gnu-soft build
PASS: glibcs-nios2-linux-gnu build
PASS: glibcs-powerpc64le-linux-gnu build
PASS: glibcs-powerpc64-linux-gnu build
PASS: glibcs-tilegxbe-linux-gnu-32 build
PASS: glibcs-tilegxbe-linux-gnu build
PASS: glibcs-tilegx-linux-gnu-32 build
PASS: glibcs-tilegx-linux-gnu build
PASS: glibcs-tilepro-linux-gnu build
and the following build failures:
FAIL: glibcs-alpha-linux-gnu build
elf/sln is failed to link due to:
assertion fail bfd/elf64-alpha.c:4125
This is caused by linker bug and/or non-PIC code in PIE libc.a.
FAIL: glibcs-hppa-linux-gnu build
elf/sln is failed to link due to:
collect2: fatal error: ld terminated with signal 11 [Segmentation fault]
https://sourceware.org/bugzilla/show_bug.cgi?id=22537
FAIL: glibcs-ia64-linux-gnu build
elf/sln is failed to link due to:
collect2: fatal error: ld terminated with signal 11 [Segmentation fault]
FAIL: glibcs-powerpc-linux-gnu build
FAIL: glibcs-powerpc-linux-gnu-soft build
FAIL: glibcs-powerpc-linux-gnuspe build
FAIL: glibcs-powerpc-linux-gnuspe-e500v1 build
elf/sln is failed to link due to:
ld: read-only segment has dynamic relocations.
This is caused by linker bug and/or non-PIC code in PIE libc.a. See:
https://sourceware.org/bugzilla/show_bug.cgi?id=22264
FAIL: glibcs-powerpc-linux-gnu-power4 build
elf/sln is failed to link due to:
findlocale.c:96:(.text+0x22c): @local call to ifunc memchr
This is caused by linker bug and/or non-PIC code in PIE libc.a.
FAIL: glibcs-s390-linux-gnu build
elf/sln is failed to link due to:
collect2: fatal error: ld terminated with signal 11 [Segmentation fault], core dumped
assertion fail bfd/elflink.c:14299
This is caused by linker bug and/or non-PIC code in PIE libc.a.
FAIL: glibcs-sh3eb-linux-gnu build
FAIL: glibcs-sh3-linux-gnu build
FAIL: glibcs-sh4eb-linux-gnu build
FAIL: glibcs-sh4eb-linux-gnu-soft build
FAIL: glibcs-sh4-linux-gnu build
FAIL: glibcs-sh4-linux-gnu-soft build
elf/sln is failed to link due to:
ld: read-only segment has dynamic relocations.
This is caused by linker bug and/or non-PIC code in PIE libc.a. See:
https://sourceware.org/bugzilla/show_bug.cgi?id=22263
Also TLS code sequence in SH assembly syscalls in glibc doesn't match TLS
code sequence expected by ld:
https://sourceware.org/bugzilla/show_bug.cgi?id=22270
FAIL: glibcs-sparc64-linux-gnu build
FAIL: glibcs-sparcv9-linux-gnu build
FAIL: glibcs-tilegxbe-linux-gnu build
FAIL: glibcs-tilegxbe-linux-gnu-32 build
FAIL: glibcs-tilegx-linux-gnu build
FAIL: glibcs-tilegx-linux-gnu-32 build
FAIL: glibcs-tilepro-linux-gnu build
elf/sln is failed to link due to:
ld: read-only segment has dynamic relocations.
This is caused by linker bug and/or non-PIC code in PIE libc.a. See:
https://sourceware.org/bugzilla/show_bug.cgi?id=22263
[BZ #19574]
* INSTALL: Regenerated.
* Makeconfig (real-static-start-installed-name): New.
(pic-default): Updated for --enable-static-pie.
(pie-default): New for --enable-static-pie.
(default-pie-ldflag): Likewise.
(+link-static-before-libc): Replace $(DEFAULT-LDFLAGS-$(@F))
with $(if $($(@F)-no-pie),$(no-pie-ldflag),$(default-pie-ldflag)).
Replace $(static-start-installed-name) with
$(real-static-start-installed-name).
(+prectorT): Updated for --enable-static-pie.
(+postctorT): Likewise.
(CFLAGS-.o): Add $(pie-default).
(CFLAGS-.op): Likewise.
* NEWS: Mention --enable-static-pie.
* config.h.in (ENABLE_STATIC_PIE): New.
* configure.ac (--enable-static-pie): New configure option.
(have-no-dynamic-linker): New LIBC_CONFIG_VAR.
(have-static-pie): Likewise.
Enable static PIE if linker supports --no-dynamic-linker.
(ENABLE_STATIC_PIE): New AC_DEFINE.
(enable-static-pie): New LIBC_CONFIG_VAR.
* configure: Regenerated.
* csu/Makefile (omit-deps): Add r$(start-installed-name) and
gr$(start-installed-name) for --enable-static-pie.
(extra-objs): Likewise.
(install-lib): Likewise.
(extra-objs): Add static-reloc.o and static-reloc.os
($(objpfx)$(start-installed-name)): Also depend on
$(objpfx)static-reloc.o.
($(objpfx)r$(start-installed-name)): New.
($(objpfx)g$(start-installed-name)): Also depend on
$(objpfx)static-reloc.os.
($(objpfx)gr$(start-installed-name)): New.
* csu/libc-start.c (LIBC_START_MAIN): Call _dl_relocate_static_pie
in libc.a.
* csu/libc-tls.c (__libc_setup_tls): Add main_map->l_addr to
initimage.
* csu/static-reloc.c: New file.
* elf/Makefile (routines): Add dl-reloc-static-pie.
(elide-routines.os): Likewise.
(DEFAULT-LDFLAGS-tst-tls1-static-non-pie): Removed.
(tst-tls1-static-non-pie-no-pie): New.
* elf/dl-reloc-static-pie.c: New file.
* elf/dl-support.c (_dl_get_dl_main_map): New function.
* elf/dynamic-link.h (ELF_DURING_STARTUP): Also check
STATIC_PIE_BOOTSTRAP.
* elf/get-dynamic-info.h (elf_get_dynamic_info): Likewise.
* gmon/Makefile (tests): Add tst-gmon-static-pie.
(tests-static): Likewise.
(DEFAULT-LDFLAGS-tst-gmon-static): Removed.
(tst-gmon-static-no-pie): New.
(CFLAGS-tst-gmon-static-pie.c): Likewise.
(CRT-tst-gmon-static-pie): Likewise.
(tst-gmon-static-pie-ENV): Likewise.
(tests-special): Likewise.
($(objpfx)tst-gmon-static-pie.out): Likewise.
(clean-tst-gmon-static-pie-data): Likewise.
($(objpfx)tst-gmon-static-pie-gprof.out): Likewise.
* gmon/tst-gmon-static-pie.c: New file.
* manual/install.texi: Document --enable-static-pie.
* sysdeps/generic/ldsodefs.h (_dl_relocate_static_pie): New.
(_dl_get_dl_main_map): Likewise.
* sysdeps/i386/configure.ac: Check if linker supports static PIE.
* sysdeps/x86_64/configure.ac: Likewise.
* sysdeps/i386/configure: Regenerated.
* sysdeps/x86_64/configure: Likewise.
* sysdeps/mips/Makefile (ASFLAGS-.o): Add $(pie-default).
(ASFLAGS-.op): Likewise.
SXID_ERASE is implicit for all environment variables. Avoid
mentioning it in the tunables list; that way only the ones with
SXID_IGNORE remain prominent and mentioned. TODO: we need to audit
each of those cases and drop them to SXID_ERASE wherever possible.
A glibc master build with --enable-nss-crypt using the NSS
crypto libraries fails during make check with the following error:
<command-line>:0:0: error: "USE_CRYPT" redefined [-Werror]
<command-line>:0:0: note: this is the location of the previous
definition
This is caused by commit 36975e8e7e
by H.J. Lu which replaces all = with +=. The fix is to undefine
USE_CRYPT before defining it to zero.
Committed as an obvious fix. Fixes the build issue on x86_64 with
no regressions.
Signed-off-by: Carlos O'Donell <carlos@redhat.com>
This patch adds several new tunables to control the behavior of
elision on supported platforms[1]. Since elision now depends
on tunables, we should always *compile* with elision enabled,
and leave the code disabled, but available for runtime
selection. This gives us *much* better compile-time testing of
the existing code to avoid bit-rot[2].
Tested on ppc, ppc64, ppc64le, s390x and x86_64.
[1] This part of the patch was initially proposed by
Paul Murphy but was "staled" because the framework have changed
since the patch was originally proposed:
https://patchwork.sourceware.org/patch/10342/
[2] This part of the patch was inititally proposed as a RFC by
Carlos O'Donnell. Make sense to me integrate this on the patch:
https://sourceware.org/ml/libc-alpha/2017-05/msg00335.html
* elf/dl-tunables.list: Add elision parameters.
* manual/tunables.texi: Add entries about elision tunable.
* sysdeps/unix/sysv/linux/powerpc/elision-conf.c:
Add callback functions to dynamically enable/disable elision.
Add multiple callbacks functions to set elision parameters.
Deleted __libc_enable_secure check.
* sysdeps/unix/sysv/linux/s390/elision-conf.c: Likewise.
* sysdeps/unix/sysv/linux/x86/elision-conf.c: Likewise.
* configure: Regenerated.
* configure.ac: Option enable_lock_elision was deleted.
* config.h.in: ENABLE_LOCK_ELISION flag was deleted.
* config.make.in: Remove references to enable_lock_elision.
* manual/install.texi: Elision configure option was removed.
* INSTALL: Regenerated to remove enable_lock_elision.
* nptl/Makefile:
Disable elision so it can verify error case for destroying a mutex.
* sysdeps/powerpc/nptl/elide.h:
Cleanup ENABLE_LOCK_ELISION check.
Deleted macros for the case when ENABLE_LOCK_ELISION was not defined.
* sysdeps/s390/configure: Regenerated.
* sysdeps/s390/configure.ac: Remove references to enable_lock_elision..
* nptl/tst-mutex8.c:
Deleted all #ifndef ENABLE_LOCK_ELISION from the test.
* sysdeps/powerpc/powerpc32/sysdep.h:
Deleted all ENABLE_LOCK_ELISION checks.
* sysdeps/powerpc/powerpc64/sysdep.h: Likewise.
* sysdeps/powerpc/sysdep.h: Likewise.
* sysdeps/s390/nptl/bits/pthreadtypes-arch.h: Likewise.
* sysdeps/unix/sysv/linux/powerpc/force-elision.h: Likewise.
* sysdeps/unix/sysv/linux/s390/elision-conf.h: Likewise.
* sysdeps/unix/sysv/linux/s390/force-elision.h: Likewise.
* sysdeps/unix/sysv/linux/s390/lowlevellock.h: Likewise.
* sysdeps/unix/sysv/linux/s390/Makefile: Remove references to
enable-lock-elision.
Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
A note header has 3 4-bytes fields, followed by note name and note
descriptor. According to gABI, in a note entry, the note name field,
not note name size, is padded for the note descriptor. And the note
descriptor field, not note descriptor size, is padded for the next
note entry. Notes are aligned to 4 bytes in 32-bit objects and 8 bytes
in 64-bit objects.
For all GNU notes, the name is "GNU" which is 4 bytes. They have the
same format in the first 16 bytes in both 32-bit and 64-bit objects.
They differ by note descriptor size and note type. So far, .note.ABI-tag
and .note.gnu.build-id notes are always aligned to 4 bytes. The exsting
codes compute the note size by aligning the note name size and note
descriptor size to 4 bytes. It happens to produce the same value as
the actual note size by luck since the name size is 4 and offset of the
note descriptor is 16. But it will produce the wrong size when note
alignment is 8 bytes in 64-bit objects.
This patch defines ELF_NOTE_DESC_OFFSET and ELF_NOTE_NEXT_OFFSET to
properly compute offsets of note descriptor and next note. It uses
alignment of PT_NOTE segment to support both 4-byte and 8-byte note
alignments in 64-bit objects. To handle PT_NOTE segments with
incorrect alignment, which may lead to an infinite loop, if segment
alignment is less than 4, we treate alignment as 4 bytes since some
note segments have 0 or 1 byte alignment.
[BZ #22370]
* elf/dl-hwcaps.c (ROUND): Removed.
(_dl_important_hwcaps): Replace ROUND with ELF_NOTE_DESC_OFFSET
and ELF_NOTE_NEXT_OFFSET.
* elf/dl-load.c (ROUND): Removed.
(open_verify): Replace ROUND with ELF_NOTE_NEXT_OFFSET.
* elf/readelflib.c (ROUND): Removed.
(process_elf_file): Replace ROUND with ELF_NOTE_NEXT_OFFSET.
* include/elf.h [!_ISOMAC]: Include <libc-pointer-arith.h>.
[!_ISOMAC] (ELF_NOTE_DESC_OFFSET): New.
[!_ISOMAC] (ELF_NOTE_NEXT_OFFSET): Likewise.
Combine the four places where link maps are sorted into a single function.
This also moves the logic to skip the first map (representing the main
binary) to the callers.
To support Intel Control-flow Enforcement Technology (CET) run-time
control:
1. An architecture specific field in the writable ld.so namespace is
needed to indicate if CET features are enabled at run-time.
2. An architecture specific field in struct link_map is needed if
CET features are enabled in an ELF module.
This patch adds dl-procruntime.c to the writable ld.so namespace and
link_map.h to struct link_map.
Tested with build-many-glibcs.py.
* elf/dl-support.c: Include <dl-procruntime.c>.
* include/link.h: Include <link_map.h>.
* sysdeps/generic/dl-procruntime.c: New file.
* sysdeps/generic/link_map.h: Likewise.
* sysdeps/generic/ldsodefs.h: Include <dl-procruntime.c> in
the writable ld.so namespace.
These static functions are not needed if a target does not do lazy
tlsdesc initialization.
* elf/tlsdeschtab.h (_dl_tls_resolve_early_return_p): Mark unused.
(_dl_tlsdesc_wake_up_held_fixups): Likewise.
Use $(LDFLAGS-$(@F)) with tst-tls1-static-non-pie may not be sufficient
when static PIE is built by default. Use $(DEFAULT-LDFLAGS-$(@F)) in
+link-static-before-libc to make sure that tst-tls1-static-non-pie is
always built as non-PIE static executable and make sure that crt1.o is
used with tst-tls1-static-non-pie.
* Makeconfig (+link-static-before-libc): Use
$(DEFAULT-LDFLAGS-$(@F)).
* elf/Makefile (CRT-tst-tls1-static-non-pie): New.
(LDFLAGS-tst-tls1-static-non-pie): Renamed to ...
(DEFAULT-LDFLAGS-tst-tls1-static-non-pie): This.
Verify that crt1.o can be used with main () in a shared object.
* elf/Makefile (tests): Add tst-main1.
(modules-names): Add tst-main1mod.
($(objpfx)tst-main1): New.
(CRT-tst-main1): Likewise.
(LDFLAGS-tst-main1): Likewise.
(LDLIBS-tst-main1): Likewise.
(tst-main1mod.so-no-z-defs): Likewise.
* elf/tst-main1.c: New file.
* elf/tst-main1mod.c: Likewise.
(&_dl_main_map) is used instead of (&bootstrap_map) to bootstrap static
PIE. Define BOOTSTRAP_MAP with (&_dl_main_map) to avoid hardcode to
(&bootstrap_map).
* elf/rtld.c (BOOTSTRAP_MAP): New.
(RESOLVE_MAP): Replace (&bootstrap_map) with BOOTSTRAP_MAP.
* sysdeps/hppa/dl-machine.h (ELF_MACHINE_BEFORE_RTLD_RELOC):
Likewise.
* sysdeps/ia64/dl-machine.h (ELF_MACHINE_BEFORE_RTLD_RELOC):
Likewise.
* sysdeps/mips/dl-machine.h (ELF_MACHINE_BEFORE_RTLD_RELOC):
Likewise.
__dl_iterate_phdr is hidden and should be accessed directly within
libc.so and libc.a without using GOT nor PLT.
[BZ #18822]
* elf/dl-iteratephdr.c (hidden_proto (__dl_iterate_phdr)): Moved
to ...
* include/link.h (hidden_proto (__dl_iterate_phdr)): Here.
tst-tls1-static-non-pie is built with $(no-pie-ldflag) to make it a
non-PIE static executable, regardless if --enable-static-pie is used
to configure glibc.
* elf/Makefile (tests-static-internal): Add
tst-tls1-static-non-pie.
(LDFLAGS-tst-tls1-static-non-pie): New.
* elf/tst-tls1-static-non-pie.c: New file.
