Adjusting the start of the relro segment in order to make it end
exactly on a page boundary runs into difficulties when sections in the
relro segment are aligned; Adjusting the start by (next_page - end)
sometimes results in more than that adjustment occurring at the end,
overrunning the page boundary. So when that occurs we try a new lower
start position by masking the adjusted start with the maximum section
alignment. However, we didn't consider that this masked start address
may in fact be before the initial relro base, which is silly since
that can only increase padding at the relro end.
I've also moved some calculations closer to where they are used, and
comments closer to the relevant statements.
* ldlang.c (lang_size_sections): When alignment of sections
results in relro base adjustment being too large, don't go lower
than the initial value.
* ldexp.c (fold_binary <DATA_SEGMENT_RELRO_END>): Comment.
* scripttempl/elf.sc (DATA_SEGMENT_ALIGN): Omit SEGMENT_SIZE
alignment when SEGMENT_SIZE is the same as MAXPAGESIZE.
Now that all targets have been converted to nrun, we can finally punt
this old inconsistent interface.
A few stray references to the old run were sprinkled about; clean them
up in the process.
We leave behind the run(1) man page mostly so that we get it updated for
the new nrun interface.
Older compilers that warn wrongly will just need -Wno-error. No way
am I going to init every single field, then have to edit this code
whenever bfd_link_hash_entry changes. Another option, making the
struct static, isn't very nice since it means larger binaries and
worse code.
* emultempl/elf32.em (gld${EMULATION_NAME}_before_allocation): Don't
init ehdr_start_save.
The ehdr_start_save variable does not need to be initialized. However,
not initializing it will trigger a compiler warning when using older
versions of GCC. Self-assignment unfortunately doesn't work for Clang
as Clang has a warning similar to -Winit-self as part of -Wall.
* emultempl/elf32.em (gld*_before_allocation): Zero-initialize
the ehdr_start_save variable.
This patch, as the subject says, extends GDB so that it is able to use
the contents of the file /proc/PID/coredump_filter when generating a
corefile. This file contains a bit mask that is a representation of
the different types of memory mappings in the Linux kernel; the user
can choose to dump or not dump a certain type of memory mapping by
enabling/disabling the respective bit in the bit mask. Currently,
here is what is supported:
bit 0 Dump anonymous private mappings.
bit 1 Dump anonymous shared mappings.
bit 2 Dump file-backed private mappings.
bit 3 Dump file-backed shared mappings.
bit 4 (since Linux 2.6.24)
Dump ELF headers.
bit 5 (since Linux 2.6.28)
Dump private huge pages.
bit 6 (since Linux 2.6.28)
Dump shared huge pages.
(This table has been taken from core(5), but you can also read about it
on Documentation/filesystems/proc.txt inside the Linux kernel source
tree).
The default value for this file, used by the Linux kernel, is 0x33,
which means that bits 0, 1, 4 and 5 are enabled. This is also the
default for GDB implemented in this patch, FWIW.
Well, reading the file is obviously trivial. The hard part, mind you,
is how to determine the types of the memory mappings. For that, I
extended the code of gdb/linux-tdep.c:linux_find_memory_regions_full and
made it rely *much more* on the information gathered from
/proc/<PID>/smaps. This file contains a "verbose dump" of the
inferior's memory mappings, and we were not using as much information as
we could from it. If you want to read more about this file, take a look
at the proc(5) manpage (I will also write a blog post soon about
everything I had to learn to get this patch done, and when I it is ready
I will post it here).
With Oleg Nesterov's help, we could improve the current algorithm for
determining whether a memory mapping is anonymous/file-backed,
private/shared. GDB now also respects the MADV_DONTDUMP flag and does
not dump the memory mapping marked as so, and will always dump
"[vsyscall]" or "[vdso]" mappings (just like the Linux kernel).
In a nutshell, what the new code is doing is:
- If the mapping is associated to a file whose name ends with
" (deleted)", or if the file is "/dev/zero", or if it is "/SYSV%08x"
(shared memory), or if there is no file associated with it, or if
the AnonHugePages: or the Anonymous: fields in the /proc/PID/smaps
have contents, then GDB considers this mapping to be anonymous.
There is a special case in this, though: if the memory mapping is a
file-backed one, but *also* contains "Anonymous:" or
"AnonHugePages:" pages, then GDB considers this mapping to be *both*
anonymous and file-backed, just like the Linux kernel does. What
that means is simple: this mapping will be dumped if the user
requested anonymous mappings *or* if the user requested file-backed
mappings to be present in the corefile.
It is worth mentioning that, from all those checks described above,
the most fragile is the one to see if the file name ends with
" (deleted)". This does not necessarily mean that the mapping is
anonymous, because the deleted file associated with the mapping may
have been a hard link to another file, for example. The Linux
kernel checks to see if "i_nlink == 0", but GDB cannot easily do
this check (as it has been discussed, GDB would need to run as root,
and would need to check the contents of the /proc/PID/map_files/
directory in order to determine whether the deleted was a hardlink
or not). Therefore, we made a compromise here, and we assume that
if the file name ends with " (deleted)", then the mapping is indeed
anonymous. FWIW, this is something the Linux kernel could do
better: expose this information in a more direct way.
- If we see the flag "sh" in the VmFlags: field (in /proc/PID/smaps),
then certainly the memory mapping is shared (VM_SHARED). If we have
access to the VmFlags, and we don't see the "sh" there, then
certainly the mapping is private. However, older Linux kernels (see
the code for more details) do not have the VmFlags field; in that
case, we use another heuristic: if we see 'p' in the permission
flags, then we assume that the mapping is private, even though the
presence of the 's' flag there would mean VM_MAYSHARE, which means
the mapping could still be private. This should work OK enough,
however.
Finally, it is worth mentioning that I added a new command, 'set
use-coredump-filter on/off'. When it is 'on', it will read the
coredump_filter' file (if it exists) and use its value; otherwise, it
will use the default value mentioned above (0x33) to decide which memory
mappings to dump.
gdb/ChangeLog:
2015-03-31 Sergio Durigan Junior <sergiodj@redhat.com>
Jan Kratochvil <jan.kratochvil@redhat.com>
Oleg Nesterov <oleg@redhat.com>
PR corefiles/16092
* linux-tdep.c: Include 'gdbcmd.h' and 'gdb_regex.h'.
New enum identifying the various options of the coredump_filter
file.
(struct smaps_vmflags): New struct.
(use_coredump_filter): New variable.
(decode_vmflags): New function.
(mapping_is_anonymous_p): Likewise.
(dump_mapping_p): Likewise.
(linux_find_memory_regions_full): New variables
'coredumpfilter_name', 'coredumpfilterdata', 'pid', 'filterflags'.
Removed variable 'modified'. Read /proc/<PID>/smaps file; improve
parsing of its information. Implement memory mapping filtering
based on its contents.
(show_use_coredump_filter): New function.
(_initialize_linux_tdep): New command 'set use-coredump-filter'.
* NEWS: Mention the possibility of using the
'/proc/PID/coredump_filter' file when generating a corefile.
Mention new command 'set use-coredump-filter'.
gdb/doc/ChangeLog:
2015-03-31 Sergio Durigan Junior <sergiodj@redhat.com>
PR corefiles/16092
* gdb.texinfo (gcore): Mention new command 'set
use-coredump-filter'.
(set use-coredump-filter): Document new command.
gdb/testsuite/ChangeLog:
2015-03-31 Sergio Durigan Junior <sergiodj@redhat.com>
PR corefiles/16092
* gdb.base/coredump-filter.c: New file.
* gdb.base/coredump-filter.exp: Likewise.
When loading a corefile that has some inaccessible memory region(s),
GDB complains about it:
(gdb) core /my/corefile
[New LWP 28468]
Cannot access memory at address 0x355fc21148
Cannot access memory at address 0x355fc21140
(gdb)
However, despite not seeing the message "Core was generated by...", it
is still possible to inspect the corefile using regular GDB commands.
The reason for that is because read_memory_unsigned_integer throws an
exception when it cannot read the memory region, but
solib_svr4_r_ldsomap was not catching it. The fix is to catch the
exception and act accordingly.
Tested on Fedora 20 x86_64, no regressions found.
gdb/ChangeLog:
2015-03-31 Sergio Durigan Junior <sergiodj@redhat.com>
* solib-svr4.c (solib_svr4_r_ldsomap): Catch possible exception by
read_memory_unsigned_integer.
This patch adds cpu information on linux based on /proc/cpuinfo as :
cpus Listing of all cpus/cores on the system
This patch also reorders the info os commands so that they are listed
in alphabetical order.
gdb/ChangeLog:
* NEWS: Mention info os cpus support.
* gdb/nat/linux-osdata.c (linux_xfer_osdata_cpus): New function.
(struct osdata_type): Add cpus entry, reorder the entries in
alphabetical order.
gdb/doc/ChangeLog:
* gdb.texinfo (Operating System Auxiliary Information): Add info os cpus
documentation, reorder the info os entries in alphabetical order.
This allows triplets where the vendor is not set.
gdb/ChangeLog:
2015-03-31 Matthias Klose <doko@ubuntu.com>
* compile/compile.c (compile_to_object): Allow triplets with or
without vendor set.
With newer versions of gcc (5.x), the extern inline we're using with the
cgen-{mem,ops} modules no longer work. Since this code really wants the
gnu inline semantics, use that attribute explicitly.
Also Change _TLS_MODULE_BASE_. Always let it point to the start
of TLS segment.
2015-03-28 Jing Yu <jingyu@google.com>
* aarch64-reloc.def: New TLSLD_ADD_DTPREL_HI12,
TLSLD_ADD_DTPREL_LO12_NC.
* aarch64.cc (Target_aarch64::define_tls_base_symbol): Always
let _TLS_MODULE_BASE_ point to the start of tls segment.
(Target_aarch64::optimize_tls_reloc): Add cases for
R_AARCH64_TLSLD_ADD_DTPREL_HI12 and
R_AARCH64_TLSLD_ADD_DTPREL_LO12_NC.
(Target_aarch64::Scan::local): Likewise.
(Target_aarch64::Scan::global): Likewise.
(Target_aarch64::Relocate::relocate): Likewise.
(Target_aarch64::Relocate::relocate_tls): Likewise. And remove
subtracting tls segment size from symbol value for
TLSLD_*_DTPREL relocations.
A lot of cpu state is stored in global variables, as is memory handling.
The sim_size support needs unwinding at some point. But at least this
is an improvement on the status quo.
In preparation for converting to nrun, call the common functions that
are needed. This doesn't produce any new warnings, and the generated
code should be the same.
gdb/ChangeLog:
* remote.c (remote_mourn_1): Remove function. Update all callers
to use remote_mourn.
(extended_remote_mourn_1): Remove function. Update all callers
to use extended_remote_mourn.
(extended_remote_attach_1): Remove function. Update all callers
to use extended_remote_attach.
Since .rela.plt/rel.plt section may contain relocations against .got.plt
section, we set sh_info for .rela.plt/rel.plt section to .got.plt section
index if target has .got.plt section.
bfd/
PR ld/18169
* elf-bfd.h (elf_backend_data): Add get_reloc_section.
(_bfd_elf_get_reloc_section): New.
* elf.c (_bfd_elf_get_reloc_section): Likewise.
(assign_section_numbers): Call get_reloc_section to look up the
section the relocs apply.
* elfxx-target.h (elf_backend_get_reloc_section): Likewise.
(elfNN_bed): Initialize get_reloc_section with
elf_backend_get_reloc_section.
ld/testsuite/
PR ld/18169
* ld-elf/linkinfo1a.d: Updated.
* ld-elf/linkinfo1b.d: Likewise.
A lot of cpu state is stored in global variables, as is memory handling.
The sim_size support needs unwinding at some point. But at least this
is an improvement on the status quo.
In preparation for converting to nrun, call the common functions that
are needed. This doesn't produce any new warnings, and the generated
code should be the same.
Looks like historical restructuring in this dir lost the d10v-elf subdir
and no one noticed in the meantime. Re-add it to the testsuite.
There are some failures, but better some tests get run than none at all.
