linux-stable.git/arch/arm64/kernel/module.lds, branch linux-4.9.y Linux kernel stable tree arm64: module: remove (NOLOAD) from linker script 2022-04-20T07:06:44+00:00 Fangrui Song maskray@google.com 2022-02-18T08:12:09+00:00 51ea21bbb41fffdeaa2c70679461a3bb256109e3 commit 4013e26670c590944abdab56c4fa797527b74325 upstream. On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually inappropriate for .plt and .text.* sections which are always SHT_PROGBITS. In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway and (NOLOAD) will be essentially ignored. In ld.lld, since https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to customize the output section type"), ld.lld will report a `section type mismatch` error. Just remove (NOLOAD) to fix the error. [1] https://lld.llvm.org/ELF/linker_script.html As of today, "The section should be marked as not loadable" on https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is outdated for ELF. Tested-by: Nathan Chancellor <nathan@kernel.org> Reported-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Fangrui Song <maskray@google.com> Acked-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20220218081209.354383-1-maskray@google.com Signed-off-by: Will Deacon <will@kernel.org> [nathan: Fix conflicts due to lack of 596b0474d3d9, be0f272bfc83, and 24af6c4e4e0f] Signed-off-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 4013e26670c590944abdab56c4fa797527b74325 upstream.

On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
inappropriate for .plt and .text.* sections which are always
SHT_PROGBITS.

In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
and (NOLOAD) will be essentially ignored. In ld.lld, since
https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
customize the output section type"), ld.lld will report a `section type
mismatch` error. Just remove (NOLOAD) to fix the error.

[1] https://lld.llvm.org/ELF/linker_script.html As of today, "The
section should be marked as not loadable" on
https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is
outdated for ELF.

Tested-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Fangrui Song <maskray@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220218081209.354383-1-maskray@google.com
Signed-off-by: Will Deacon <will@kernel.org>
[nathan: Fix conflicts due to lack of 596b0474d3d9, be0f272bfc83, and 24af6c4e4e0f]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arm64: add support for module PLTs 2016-02-24T14:57:24+00:00 Ard Biesheuvel ard.biesheuvel@linaro.org 2015-11-24T11:37:35+00:00 fd045f6cd98ec4953147b318418bd45e441e52a3 This adds support for emitting PLTs at module load time for relative branches that are out of range. This is a prerequisite for KASLR, which may place the kernel and the modules anywhere in the vmalloc area, making it more likely that branch target offsets exceed the maximum range of +/- 128 MB. In this version, I removed the distinction between relocations against .init executable sections and ordinary executable sections. The reason is that it is hardly worth the trouble, given that .init.text usually does not contain that many far branches, and this version now only reserves PLT entry space for jump and call relocations against undefined symbols (since symbols defined in the same module can be assumed to be within +/- 128 MB) For example, the mac80211.ko module (which is fairly sizable at ~400 KB) built with -mcmodel=large gives the following relocation counts: relocs branches unique !local .text 3925 3347 518 219 .init.text 11 8 7 1 .exit.text 4 4 4 1 .text.unlikely 81 67 36 17 ('unique' means branches to unique type/symbol/addend combos, of which !local is the subset referring to undefined symbols) IOW, we are only emitting a single PLT entry for the .init sections, and we are better off just adding it to the core PLT section instead. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> 
This adds support for emitting PLTs at module load time for relative
branches that are out of range. This is a prerequisite for KASLR, which
may place the kernel and the modules anywhere in the vmalloc area,
making it more likely that branch target offsets exceed the maximum
range of +/- 128 MB.

In this version, I removed the distinction between relocations against
.init executable sections and ordinary executable sections. The reason
is that it is hardly worth the trouble, given that .init.text usually
does not contain that many far branches, and this version now only
reserves PLT entry space for jump and call relocations against undefined
symbols (since symbols defined in the same module can be assumed to be
within +/- 128 MB)

For example, the mac80211.ko module (which is fairly sizable at ~400 KB)
built with -mcmodel=large gives the following relocation counts:

                    relocs    branches   unique     !local
  .text              3925       3347       518        219
  .init.text           11          8         7          1
  .exit.text            4          4         4          1
  .text.unlikely       81         67        36         17

('unique' means branches to unique type/symbol/addend combos, of which
!local is the subset referring to undefined symbols)

IOW, we are only emitting a single PLT entry for the .init sections, and
we are better off just adding it to the core PLT section instead.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>