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

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: https://github.com/llvm/llvm-project/commit/381599f1fe973afad3094e55ec99b1620dba7d8c
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>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 202dbd17ad2ff455eb9fc214f7e4b1de967ea9e1..25ed6f1a7c7ae54cae3102c66257de598f04db3c 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -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

diff --git a/arch/arm/include/asm/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h
index 89697f2047159a11110c8cc4ed006cbb70b67a06..a54db342653ab0fcaa3a42ae4f7d4e8587e4c8ff 100644 (file)
--- a/arch/arm/include/asm/vmlinux.lds.h
+++ b/arch/arm/include/asm/vmlinux.lds.h
@@ -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);                                \

diff --git a/init/Kconfig b/init/Kconfig
index d0d021b3fa3b3da5576421b4e1c63baf6c8afc09..fc994f5cd5dba8d7a6c76c4d2b05ae110f27271e 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -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