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The original discussion was here, https://github.com/riscv/riscv-elf-psabi-doc/issues/184 After discussing with Kito Cheng, I think the addends of %pcrel_hi and %pcrel_lo are both allowed in GNU toolchain. However, both of the them mean the offset of symbols, rather than the pc address. But the addends of %got_pcrel_hi and it's %pcrel_lo do not look reasonable. I believe gcc won't generate the got patterns with addends, so linker should report dangerous relocation errors, in case the assembly code use them. Another issue was here, https://sourceware.org/pipermail/binutils/2021-June/116983.html At the beginnig, I suppose %pcrel_hi and %pcrel_lo are valid only when they are in the same input section. But Jim Wilson points out that gcc may generate %hi and %lo in the different input sections, when -freorder-blocks-and-partition option is used. So that a memory references for a loop may have the %hi outside the loop, but the %lo remain in the loop. However, it is hard to create the testcases, to see if %pcrel_hi and %pcrel_lo have the same behavior. Unfortunately, I notice that the current pcrel resolver cannot work for the above case. For now we build a hash table for pcrel at the start of riscv_elf_relocate_section, and then free the hash at the end. But riscv_elf_relocate_section only handles an input section at a time, so that means we can only resolve the %pcrel_hi and %pcrel_lo which are in the same input section. Otherwise, like the above case, we will report "%pcrel_lo missing matching %pcrel_hi" for them. I have no plan to improve this in the short-term, so maybe we can wait until someone meets the problem before we deal with it. bfd/ * elfnn-riscv.c (riscv_pcrel_hi_reloc): Added field to store the original relocation type, in case the type is converted to R_RISCV_HI20. (riscv_pcrel_lo_reloc): Removed unused name field. (riscv_pcrel_relocs): Added comments. (riscv_zero_pcrel_hi_reloc): Removed unused input_bfd. (riscv_record_pcrel_hi_reloc): Updated. (riscv_record_pcrel_lo_reloc): Likewise. (riscv_resolve_pcrel_lo_relocs): Likewise. Check the original type of auipc, to make sure the %pcrel_lo without any addends. Otherwise, report dangerous relocation error. (riscv_elf_relocate_section): Updated above functions are changed. For R_RISCV_GOT_HI20, report dangerous relocation error when addend isn't zero. ld/ * testsuite/ld-riscv-elf/ld-riscv-elf.exp: Updated. * testsuite/ld-riscv-elf/pcrel-lo-addend-3a.d: New testcase. * testsuite/ld-riscv-elf/pcrel-lo-addend-3a.s: Likewise. * testsuite/ld-riscv-elf/pcrel-lo-addend-3b.d: New testcase. Should report error since the %pcrel_lo with addend refers to %got_pcrel_hi. * testsuite/ld-riscv-elf/pcrel-lo-addend-3b.s: Likewise. * testsuite/ld-riscv-elf/pcrel-lo-addend-3c.d: New testcase. Should report error since the %got_pcrel_hi with addend. * testsuite/ld-riscv-elf/pcrel-lo-addend-3c.s: Likewise. * testsuite/ld-riscv-elf/pcrel-lo-addend-3.ld: Likewise. |
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README for LD
This is the GNU linker. It is distributed with other "binary
utilities" which should be in ../binutils. See ../binutils/README for
more general notes, including where to send bug reports.
There are many features of the linker:
* The linker uses a Binary File Descriptor library (../bfd)
that it uses to read and write object files. This helps
insulate the linker itself from the format of object files.
* The linker supports a number of different object file
formats. It can even handle multiple formats at once:
Read two input formats and write a third.
* The linker can be configured for cross-linking.
* The linker supports a control language.
* There is a user manual (ld.texi), as well as the
beginnings of an internals manual (ldint.texi).
Installation
============
See ../binutils/README.
If you want to make a cross-linker, you may want to specify
a different search path of -lfoo libraries than the default.
You can do this by setting the LIB_PATH variable in ./Makefile
or using the --with-lib-path configure switch.
To build just the linker, make the target all-ld from the top level
directory (one directory above this one).
Porting to a new target
=======================
See the ldint.texi manual.
Reporting bugs etc
===========================
See ../binutils/README.
Known problems
==============
The Solaris linker normally exports all dynamic symbols from an
executable. The GNU linker does not do this by default. This is
because the GNU linker tries to present the same interface for all
similar targets (in this case, all native ELF targets). This does not
matter for normal programs, but it can make a difference for programs
which try to dlopen an executable, such as PERL or Tcl. You can make
the GNU linker export all dynamic symbols with the -E or
--export-dynamic command line option.
HP/UX 9.01 has a shell bug that causes the linker scripts to be
generated incorrectly. The symptom of this appears to be "fatal error
- scanner input buffer overflow" error messages. There are various
workarounds to this:
* Build and install bash, and build with "make SHELL=bash".
* Update to a version of HP/UX with a working shell (e.g., 9.05).
* Replace "(. ${srcdir}/scripttempl/${SCRIPT_NAME}.sc)" in
genscripts.sh with "sh ${srcdir}..." (no parens) and make sure the
emulparams script used exports any shell variables it sets.
Copyright (C) 2012-2021 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.