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ARM: 9443/1: Require linker to support KEEP within OVERLAY for DCE

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ld.lld prior to 21.0.0 does not support using the KEEP keyword within an
overlay description, which may be needed to avoid discarding necessary
sections within an overlay with '--gc-sections', which can be enabled
for the kernel via CONFIG_LD_DEAD_CODE_DATA_ELIMINATION.

Disallow CONFIG_LD_DEAD_CODE_DATA_ELIMINATION without support for KEEP
within OVERLAY and introduce a macro, OVERLAY_KEEP, that can be used to
conditionally add KEEP when it is properly supported to avoid breaking
old versions of ld.lld.

Cc: stable@vger.kernel.org
Link: 381599f1fe
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Nathan Chancellor 2025-03-20 22:33:49 +01:00 committed by Russell King (Oracle)
parent 9cac324d6f
commit e7607f7d6d
3 changed files with 12 additions and 1 deletions
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2
arch/arm/Kconfig
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@ -121,7 +121,7 @@ config ARM
select HAVE_KERNEL_XZ
select HAVE_KPROBES if !XIP_KERNEL && !CPU_ENDIAN_BE32 && !CPU_V7M
select HAVE_KRETPROBES if HAVE_KPROBES
select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if (LD_VERSION >= 23600 || LD_IS_LLD)
select HAVE_LD_DEAD_CODE_DATA_ELIMINATION if (LD_VERSION >= 23600 || LD_CAN_USE_KEEP_IN_OVERLAY)
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_NMI
select HAVE_OPTPROBES if !THUMB2_KERNEL

6
arch/arm/include/asm/vmlinux.lds.h
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@ -34,6 +34,12 @@
#define NOCROSSREFS
#endif
#ifdef CONFIG_LD_CAN_USE_KEEP_IN_OVERLAY
#define OVERLAY_KEEP(x) KEEP(x)
#else
#define OVERLAY_KEEP(x) x
#endif
/* Set start/end symbol names to the LMA for the section */
#define ARM_LMA(sym, section) \
sym##_start = LOADADDR(section); \

5
init/Kconfig
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@ -129,6 +129,11 @@ config CC_HAS_COUNTED_BY
# https://github.com/llvm/llvm-project/pull/112636
depends on !(CC_IS_CLANG && CLANG_VERSION < 190103)
config LD_CAN_USE_KEEP_IN_OVERLAY
# ld.lld prior to 21.0.0 did not support KEEP within an overlay description
# https://github.com/llvm/llvm-project/pull/130661
def_bool LD_IS_BFD || LLD_VERSION >= 210000
config RUSTC_HAS_COERCE_POINTEE
def_bool RUSTC_VERSION >= 108400