linux-toradex.git/include/linux/module.h, branch v5.10-rc3

module: use hidden visibility for weak symbol references

2020-10-28T14:08:54+00:00

Geert reports that commit be2881824ae9eb92 ("arm64/build: Assert for
unwanted sections") results in build errors on arm64 for configurations
that have CONFIG_MODULES disabled.

The commit in question added ASSERT()s to the arm64 linker script to
ensure that linker generated sections such as .got.plt etc are empty,
but as it turns out, there are corner cases where the linker does emit
content into those sections. More specifically, weak references to
function symbols (which can remain unsatisfied, and can therefore not
be emitted as relative references) will be emitted as GOT and PLT
entries when linking the kernel in PIE mode (which is the case when
CONFIG_RELOCATABLE is enabled, which is on by default).

What happens is that code such as

	struct device *(*fn)(struct device *dev);
	struct device *iommu_device;

	fn = symbol_get(mdev_get_iommu_device);
	if (fn) {
		iommu_device = fn(dev);

essentially gets converted into the following when CONFIG_MODULES is off:

	struct device *iommu_device;

	if (&mdev_get_iommu_device) {
		iommu_device = mdev_get_iommu_device(dev);

where mdev_get_iommu_device is emitted as a weak symbol reference into
the object file. The first reference is decorated with an ordinary
ABS64 data relocation (which yields 0x0 if the reference remains
unsatisfied). However, the indirect call is turned into a direct call
covered by a R_AARCH64_CALL26 relocation, which is converted into a
call via a PLT entry taking the target address from the associated
GOT entry.

Given that such GOT and PLT entries are unnecessary for fully linked
binaries such as the kernel, let's give these weak symbol references
hidden visibility, so that the linker knows that the weak reference
via R_AARCH64_CALL26 can simply remain unsatisfied.

Signed-off-by: Ard Biesheuvel 
Tested-by: Geert Uytterhoeven 
Reviewed-by: Fangrui Song 
Acked-by: Jessica Yu 
Cc: Jessica Yu 
Cc: Kees Cook 
Cc: Geert Uytterhoeven 
Cc: Nick Desaulniers 
Link: https://lore.kernel.org/r/20201027151132.14066-1-ardb@kernel.org
Signed-off-by: Will Deacon

treewide: Convert macro and uses of section(foo) to section("foo")

2020-10-25T21:51:49+00:00

Use a more generic form for __section that requires quotes to avoid
complications with clang and gcc differences.

Remove the quote operator # from compiler_attributes.h __section macro.

Convert all unquoted __section(foo) uses to quoted __section("foo").
Also convert __attribute__((section("foo"))) uses to __section("foo")
even if the __attribute__ has multiple list entry forms.

Conversion done using the script at:

    https://lore.kernel.org/lkml/75393e5ddc272dc7403de74d645e6c6e0f4e70eb.camel@perches.com/2-convert_section.pl

Signed-off-by: Joe Perches 
Reviewed-by: Nick Desaulniers 
Reviewed-by: Miguel Ojeda 
Signed-off-by: Linus Torvalds

static_call: Add inline static call infrastructure

2020-09-01T07:58:04+00:00

Add infrastructure for an arch-specific CONFIG_HAVE_STATIC_CALL_INLINE
option, which is a faster version of CONFIG_HAVE_STATIC_CALL.  At
runtime, the static call sites are patched directly, rather than using
the out-of-line trampolines.

Compared to out-of-line static calls, the performance benefits are more
modest, but still measurable.  Steven Rostedt did some tracepoint
measurements:

  https://lkml.kernel.org/r/20181126155405.72b4f718@gandalf.local.home

This code is heavily inspired by the jump label code (aka "static
jumps"), as some of the concepts are very similar.

For more details, see the comments in include/linux/static_call.h.

[peterz: simplified interface; merged trampolines]

Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Reviewed-by: Steven Rostedt (VMware) 
Cc: Linus Torvalds 
Link: https://lore.kernel.org/r/20200818135804.684334440@infradead.org

modules: inherit TAINT_PROPRIETARY_MODULE

2020-08-05T08:31:28+00:00

If a TAINT_PROPRIETARY_MODULE exports symbol, inherit the taint flag
for all modules importing these symbols, and don't allow loading
symbols from TAINT_PROPRIETARY_MODULE modules if the module previously
imported gplonly symbols.  Add a anti-circumvention devices so people
don't accidentally get themselves into trouble this way.

Comment from Greg:
  "Ah, the proven-to-be-illegal "GPL Condom" defense :)"

[jeyu: pr_info -> pr_err and pr_warn as per discussion]
Link: http://lore.kernel.org/r/20200730162957.GA22469@lst.de
Acked-by: Daniel Vetter 
Reviewed-by: Greg Kroah-Hartman 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Jessica Yu

modules: return licensing information from find_symbol

2020-08-01T14:05:02+00:00

Report the GPLONLY status through a new argument.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Jessica Yu

modules: rename the licence field in struct symsearch to license

2020-08-01T14:05:02+00:00

Use the same spelling variant as the rest of the file.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Jessica Yu

modules: mark each_symbol_section static

2020-08-01T14:05:00+00:00

each_symbol_section is only used inside of module.c.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Jessica Yu

modules: mark find_symbol static

2020-08-01T14:04:59+00:00

find_symbol is only used in module.c.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Jessica Yu

modules: mark ref_module static

2020-08-01T14:04:55+00:00

ref_module isn't used anywhere outside of module.c.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Jessica Yu

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching

2020-06-04T18:13:03+00:00

Pull livepatching updates from Jiri Kosina:

 - simplifications and improvements for issues Peter Ziljstra found
   during his previous work on W^X cleanups.

   This allows us to remove livepatch arch-specific .klp.arch sections
   and add proper support for jump labels in patched code.

   Also, this patchset removes the last module_disable_ro() usage in the
   tree.

   Patches from Josh Poimboeuf and Peter Zijlstra

 - a few other minor cleanups

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching:
  MAINTAINERS: add lib/livepatch to LIVE PATCHING
  livepatch: add arch-specific headers to MAINTAINERS
  livepatch: Make klp_apply_object_relocs static
  MAINTAINERS: adjust to livepatch .klp.arch removal
  module: Make module_enable_ro() static again
  x86/module: Use text_mutex in apply_relocate_add()
  module: Remove module_disable_ro()
  livepatch: Remove module_disable_ro() usage
  x86/module: Use text_poke() for late relocations
  s390/module: Use s390_kernel_write() for late relocations
  s390: Change s390_kernel_write() return type to match memcpy()
  livepatch: Prevent module-specific KLP rela sections from referencing vmlinux symbols
  livepatch: Remove .klp.arch
  livepatch: Apply vmlinux-specific KLP relocations early
  livepatch: Disallow vmlinux.ko