Ard Biesheuvel 13150bc541 module: use hidden visibility for weak symbol references ... Geert reports that commit be2881824a ("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 <ardb@kernel.org> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Fangrui Song <maskray@google.com> Acked-by: Jessica Yu <jeyu@kernel.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Link: https://lore.kernel.org/r/20201027151132.14066-1-ardb@kernel.org Signed-off-by: Will Deacon <will@kernel.org>		2020-10-28 14:08:54 +00:00
..
acpi	pci-v5.10-changes	2020-10-22 12:41:00 -07:00
asm-generic	treewide: Convert macro and uses of __section(foo) to __section("foo")	2020-10-25 14:51:49 -07:00
clocksource
crypto	X.509: Fix modular build of public_key_sm2	2020-10-08 16:39:14 +11:00
drm	sound updates for 5.10	2020-10-15 11:07:44 -07:00
dt-bindings	ARM: Devicetree updates	2020-10-24 10:44:18 -07:00
keys
kunit	treewide: Convert macro and uses of __section(foo) to __section("foo")	2020-10-25 14:51:49 -07:00
kvm	ARM:	2020-10-23 11:17:56 -07:00
linux	module: use hidden visibility for weak symbol references	2020-10-28 14:08:54 +00:00
math-emu
media	ARM: SoC platform updates	2020-10-24 10:33:08 -07:00
memory
misc
net	Fixes for 5.10-rc1 from the networking tree:	2020-10-23 12:05:49 -07:00
pcmcia
ras	mm,hwpoison: introduce MF_MSG_UNSPLIT_THP	2020-10-16 11:11:17 -07:00
rdma	RDMA: Explicitly pass in the dma_device to ib_register_device	2020-10-16 13:53:46 -03:00
scsi	SCSI misc on 20201023	2020-10-23 16:19:02 -07:00
soc	ARM: SoC-related driver updates	2020-10-24 10:39:22 -07:00
sound	ASoC: Updates for v5.10	2020-10-12 16:08:57 +02:00
target
trace	treewide: Convert macro and uses of __section(foo) to __section("foo")	2020-10-25 14:51:49 -07:00
uapi	A single fix to compute the field offset of the SNOOPX bit in the data	2020-10-25 11:22:59 -07:00
vdso
video
xen	xen: branch for v5.10-rc1c	2020-10-25 10:55:35 -07:00