When reserving copy relocation space for a shared symbol, scan the DSO's
program headers to see if the symbol is in a read-only segment. If so,
reserve space for that symbol in a new synthetic section named .bss.rel.ro
which will be covered by the relro program header.

This fixes the security issue disclosed on the binutils mailing list at:
https://sourceware.org/ml/libc-alpha/2016-12/msg00914.html

Differential Revision: https://reviews.llvm.org/D28272

llvm-svn: 291524

This is in preparation for my next change, which will introduce a relro
nobits section. That requires that relro sections appear at the end of the
progbits part of the r/w segment so that the relro nobits section can appear
contiguously.

Because of the amount of churn required in the test suite, I'm making this
change separately.

llvm-svn: 291523

This patch enables something like "-o /dev/null".
Previouly, it failed because such files cannot be renamed.

Differential Revision: https://reviews.llvm.org/D28010

llvm-svn: 291496

The glibc dynamic loader rounds the size down, so without this the loader
will fail to change the memory protection for the last page.

Differential Revision: https://reviews.llvm.org/D28267

llvm-svn: 290986

llvm-svn: 290932

llvm-svn: 290510

DefinedSynthetic is not created for a real ELF object, so it doesn't
have to be a template function. It has a virtual st_value, which is
either 32 bit or 64 bit, but we can simply use 64 bit.

llvm-svn: 290241

llvm-svn: 290215

That was requested by Mark Kettenis in llvm-dev:

"It is the intention that .openbsd.randomdata sections are made
read-only after initialization. The native (ld.bfd based) OpenBSD
toolchain accomplishes this by including .openbsd.randomdata into the
PT_GNU_RELRO segment."

He suggested code change, I added testcase.

Differential revision: https://reviews.llvm.org/D27974

llvm-svn: 290174

That variable was of type DenseMap<StringRef, unsigned>, but the
unsigned numbers needed to be monotonicly increasing numbers because
the implementation that used the variable depended on that fact.
That was an implementation detail and shouldn't have leaked into Config.

This patch simplifies its type to std::vector<StringRef>.

llvm-svn: 290151

This handles all the corner cases if setting a section address:

- If the address is too low, we cannot allocate the program headers.
- If the load address is lowered, we have to do that before finalize

This also shares some code with the linker script since it was already
hitting similar cases.

This is used by the freebsd boot loader. It is not clear if we need to
support this with a non binary output, but it is not as bad as I was
expecting.

llvm-svn: 290136

--retain-symbols-file=filename
Retain only the symbols listed in the file filename, discarding all others. 
filename is simply a flat file, with one symbol name per line. This option 
is especially useful in environments (such as VxWorks) where a large global 
symbol table is accumulated gradually, to conserve run-time memory.

Note: though documentation says "--retain-symbols-file does not discard 
undefined symbols, or symbols needed for relocations.", both bfd and gold 
do that, and this patch too, like testcase show.

Differential revision: https://reviews.llvm.org/D27716

llvm-svn: 290122

llvm-svn: 290115

Use of CachedHashStringRef makes sense only when we reuse hash values.
Sprinkling it to all DenseMap has no benefits and just complicates data types.
Basically we shouldn't use CachedHashStringRef unless there is a strong
reason to to do so.

llvm-svn: 290076

I thought for a while about how to remove it, but it looks like we
can just copy the file for now. Of course I'm not happy about that,
but it's just less than 50 lines of code, and we already have
duplicate code in Error.h and some other places. I want to solve
them all at once later.

Differential Revision: https://reviews.llvm.org/D27819

llvm-svn: 290062

llvm-svn: 289471

llvm-svn: 289084

This change introduces new synthetic sections IpltSection, IgotPltSection
that represent the ifunc entries that would previously have been put in
the PltSection and the GotPltSection. The separation makes sure that
the R_*_IRELATIVE relocations are placed after the non R_*_IRELATIVE
relocations, which permits ifunc resolvers to know that the .got.plt
slots will be initialized prior to the resolver being called.

A secondary benefit is that for ARM we can move the IgotPltSection and its
dynamic relocations to the .got and .rel.dyn as the ARM glibc expects all
the R_*_IRELATIVE relocations to be in the .rel.dyn

Differential revision: https://reviews.llvm.org/D27406

llvm-svn: 289045

These MIPS specific symbols should be global because in general they can
have an arbitrary value. By default this value is a fixed offset from .got
section.

This patch adds more checks to the mips-gp-local.s test case but marks
it as XFAIL because LLD does not allow redefinition of absolute symbols
value by a linker script. This should be fixed by D27276.

Differential revision: https://reviews.llvm.org/D27524

llvm-svn: 289025

Thanks to George Rimar for pointing it out.

llvm-svn: 289020

llvm-svn: 288971

Found by inspection.

llvm-svn: 288970

Config->WarnMissingEntry is a single-purpose boolean variable, and
I think it's easier to understand than Config->HasEntry.

llvm-svn: 288883

This patch is to parse the entry symbol name lazily.

llvm-svn: 288882

Shared libraries should have entry set following the same rules as for
regular binaries. The only difference is that in case the default entry
point (_start or __start) isn't found (unless it was set explicitly), we
shouldn't give a warning as in case of regular binaries.

Differential Revision: https://reviews.llvm.org/D27497

llvm-svn: 288878

If we do, the freebsd dynamic linker tries to call mmap with a size 0,
which fails.

It is hard to avoid creating them when linker scripts are used, so we
just delete empty PT_LOADs at the end.

llvm-svn: 288808

That patch broke build.

llvm-svn: 288708

llvm-svn: 288707

On Linux (and probably on other Unix-like systems), unlink(2) is
noticeably slow. It takes 250 milliseconds to remove a 1 GB file
on ext4 filesystem on my machine, whether the file is on SSD or
on a spinning disk.

To create a new result file, we remove existing file first. So, if
you repeatedly link a 1 GB program in a regular compile-link-debug
cycle, every cycle wastes 250 milliseconds only to remove a file.

Since LLD can link a 1 GB in about 5 seconds, that waste actually
matters.

This patch defines `unlinkAsync` function. The function spawns a
background thread to call unlink. The calling thread returns
almost immediately.

Differential Revision: https://reviews.llvm.org/D27295

llvm-svn: 288680

Binary output feature is a bit confuzing. bfd and gold output differs a lot sometimes,
though it is important for FreeBSD mbr loaders.

Patch change the way how we compute file offsets for binary output.
This fixes PR31196.

Previously offsets were calculated basing on offsets and addresses of sections
from the same loads:
if (Sec == First)
  return alignTo(Off, Target->MaxPageSize, Sec->Addr);
return First->Offset + Sec->Addr - First->Addr;

bfd assigns offsets for each section to VA - MinVA:
https://github.com/redox-os/binutils-gdb/blob/master/bfd/binary.c#L27
https://github.com/redox-os/binutils-gdb/blob/master/bfd/binary.c#L255 
(LMA == VA usually)

This patch for now just stops creating phdrs for binary output. 
An effect from this that no any additional calculation for offset is performed:

uintX_t getFileAlignment(uintX_t Off, OutputSectionBase *Sec) {
OutputSectionBase *First = Sec->FirstInPtLoad;
// If the section is not in a PT_LOAD, we have no other constraint.
if (!First)
  return Off; //**First is always null, condition always happens**

That is enough now with combination of another patch to generate output
that is similar to what bfd produce for mbr loader.

Differential revision: https://reviews.llvm.org/D27341

llvm-svn: 288580

This change continues what was started by D27040
Now all allocatable synthetics should be available from script side.

Differential revision: https://reviews.llvm.org/D27131

llvm-svn: 288150

-N (-omagic)
  Set the text and data sections to be readable and writable. 
  Also, do not page-align the data segment.

Differential revision: https://reviews.llvm.org/D26888

llvm-svn: 288123

Differential revision: https://reviews.llvm.org/D27097

llvm-svn: 288114

That unifies handling cases when we have SECTIONS and when
-no-rosegment is given in compareSectionsNonScript()

Now Config->SingleRoRx is used for check, testcase is provided.

llvm-svn: 288022

--no-rosegment: Do not put read-only non-executable sections in their own segment

Differential revision: https://reviews.llvm.org/D26889

llvm-svn: 288020

Unfortunatelly PT_ARM_EXIDX is special. There is no way to create it
from linker scripts, so we have to create it even if PHDRS is used.

This matches bfd and is required for the lld output to survive bfd's strip.

llvm-svn: 288012

This is important for cases like:

  .sdata        : {
    *(.got.plt .got)
...
  }

That was not supported before as there was no way to get access to 
synthetic sections from script.

More details on review page.

Differential revision: https://reviews.llvm.org/D27040

llvm-svn: 287913

    
The .ARM.exidx table has an entry for each function with the first entry
giving the start address of the function, the table is sorted in ascending
order of function address. Given a PC value, the unwinder will search the
table for the entry that contains the PC value.
    
If the table entry happens to be the last, the range of the addresses that
the final unwinding table describes will extend to the end of the address
space. To prevent an incorrect address outside the address range of the
program matching the last entry we follow ld.bfd's example and add a
sentinel EXIDX_CANTUNWIND entry at the end of the table. This gives the
final real table entry an upper bound.
    
In addition the llvm libunwind unwinder currently depends on the presence
of a sentinel entry (PR31091).

Differential revision: https://reviews.llvm.org/D26977

llvm-svn: 287869

HasError was always true if ErrorCount > 0, so we can use ErrorCount instead.

llvm-svn: 287849

Previously, if a symbol specified by -e or ENTRY() is not found,
we didn't set entry point address. That is incompatible with GNU
because GNU linkers set the first address of .text to entry.
This patch implement that behavior.

llvm-svn: 287836