diff options
| author | Ard Biesheuvel <ardb@kernel.org> | 2025-03-11 12:06:19 +0100 |
|---|---|---|
| committer | Masahiro Yamada <masahiroy@kernel.org> | 2025-03-17 00:29:50 +0900 |
| commit | 9b400d17259b70d1d68585028e96b30152d0796a (patch) | |
| tree | dd967c6890ffd783ee65b3b3b749c0122bb514f0 | |
| parent | e22bbb8e97846bfb5a6942a2322f0237ff13df0f (diff) | |
kbuild: Introduce Kconfig symbol for linking vmlinux with relocations
Some architectures build vmlinux with static relocations preserved, but
strip them again from the final vmlinux image. Arch specific tools
consume these static relocations in order to construct relocation tables
for KASLR.
The fact that vmlinux is created, consumed and subsequently updated goes
against the typical, declarative paradigm used by Make, which is based
on rules and dependencies. So as a first step towards cleaning this up,
introduce a Kconfig symbol to declare that the arch wants to consume the
static relocations emitted into vmlinux. This will be wired up further
in subsequent patches.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
| -rw-r--r-- | Makefile | 4 | ||||
| -rw-r--r-- | arch/Kconfig | 7 | ||||
| -rw-r--r-- | arch/mips/Kconfig | 1 | ||||
| -rw-r--r-- | arch/mips/Makefile | 4 | ||||
| -rw-r--r-- | arch/riscv/Kconfig | 1 | ||||
| -rw-r--r-- | arch/riscv/Makefile | 2 | ||||
| -rw-r--r-- | arch/s390/Kconfig | 1 | ||||
| -rw-r--r-- | arch/s390/Makefile | 2 | ||||
| -rw-r--r-- | arch/x86/Kconfig | 1 | ||||
| -rw-r--r-- | arch/x86/Makefile | 6 |
10 files changed, 17 insertions, 12 deletions
@@ -1120,6 +1120,10 @@ ifdef CONFIG_LD_ORPHAN_WARN LDFLAGS_vmlinux += --orphan-handling=$(CONFIG_LD_ORPHAN_WARN_LEVEL) endif +ifneq ($(CONFIG_ARCH_VMLINUX_NEEDS_RELOCS),) +LDFLAGS_vmlinux += --emit-relocs --discard-none +endif + # Align the bit size of userspace programs with the kernel KBUILD_USERCFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS)) KBUILD_USERLDFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS)) diff --git a/arch/Kconfig b/arch/Kconfig index b8a4ff365582..101a13fcde8e 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1695,6 +1695,13 @@ config ARCH_HAS_KERNEL_FPU_SUPPORT Architectures that select this option can run floating-point code in the kernel, as described in Documentation/core-api/floating-point.rst. +config ARCH_VMLINUX_NEEDS_RELOCS + bool + help + Whether the architecture needs vmlinux to be built with static + relocations preserved. This is used by some architectures to + construct bespoke relocation tables for KASLR. + source "kernel/gcov/Kconfig" source "scripts/gcc-plugins/Kconfig" diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 1924f2d83932..5aedbd7afadb 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -2617,6 +2617,7 @@ config RELOCATABLE CPU_MIPS32_R6 || CPU_MIPS64_R6 || \ CPU_P5600 || CAVIUM_OCTEON_SOC || \ CPU_LOONGSON64 + select ARCH_VMLINUX_NEEDS_RELOCS help This builds a kernel image that retains relocation information so it can be loaded someplace besides the default 1MB. diff --git a/arch/mips/Makefile b/arch/mips/Makefile index be8cb44a89fd..d9057e29bc62 100644 --- a/arch/mips/Makefile +++ b/arch/mips/Makefile @@ -100,10 +100,6 @@ LDFLAGS_vmlinux += -G 0 -static -n -nostdlib KBUILD_AFLAGS_MODULE += -mlong-calls KBUILD_CFLAGS_MODULE += -mlong-calls -ifeq ($(CONFIG_RELOCATABLE),y) -LDFLAGS_vmlinux += --emit-relocs -endif - cflags-y += -ffreestanding cflags-$(CONFIG_CPU_BIG_ENDIAN) += -EB diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 7612c52e9b1e..6f5800114416 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -1077,6 +1077,7 @@ config RELOCATABLE bool "Build a relocatable kernel" depends on MMU && 64BIT && !XIP_KERNEL select MODULE_SECTIONS if MODULES + select ARCH_VMLINUX_NEEDS_RELOCS help This builds a kernel as a Position Independent Executable (PIE), which retains all relocation metadata required to relocate the diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index 13fbc0f94238..6ef0d10e0c50 100644 --- a/arch/riscv/Makefile +++ b/arch/riscv/Makefile @@ -8,7 +8,7 @@ LDFLAGS_vmlinux := -z norelro ifeq ($(CONFIG_RELOCATABLE),y) - LDFLAGS_vmlinux += -shared -Bsymbolic -z notext --emit-relocs + LDFLAGS_vmlinux += -shared -Bsymbolic -z notext KBUILD_CFLAGS += -fPIE endif ifeq ($(CONFIG_DYNAMIC_FTRACE),y) diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 9c9ec08d78c7..ea67b7317138 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -630,6 +630,7 @@ endchoice config RELOCATABLE def_bool y + select ARCH_VMLINUX_NEEDS_RELOCS help This builds a kernel image that retains relocation information so it can be loaded at an arbitrary address. diff --git a/arch/s390/Makefile b/arch/s390/Makefile index 5fae311203c2..d5f4be440879 100644 --- a/arch/s390/Makefile +++ b/arch/s390/Makefile @@ -15,7 +15,7 @@ KBUILD_CFLAGS_MODULE += -fPIC KBUILD_AFLAGS += -m64 KBUILD_CFLAGS += -m64 KBUILD_CFLAGS += -fPIC -LDFLAGS_vmlinux := -no-pie --emit-relocs --discard-none +LDFLAGS_vmlinux := -no-pie extra_tools := relocs aflags_dwarf := -Wa,-gdwarf-2 KBUILD_AFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -D__ASSEMBLY__ diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 0e27ebd7e36a..57fc0e7635c9 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2200,6 +2200,7 @@ config RANDOMIZE_BASE config X86_NEED_RELOCS def_bool y depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE) + select ARCH_VMLINUX_NEEDS_RELOCS config PHYSICAL_ALIGN hex "Alignment value to which kernel should be aligned" diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 5b773b34768d..f65ed6dcd6fb 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -251,12 +251,6 @@ endif KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE) -ifdef CONFIG_X86_NEED_RELOCS -LDFLAGS_vmlinux := --emit-relocs --discard-none -else -LDFLAGS_vmlinux := -endif - # # The 64-bit kernel must be aligned to 2MB. Pass -z max-page-size=0x200000 to # the linker to force 2MB page size regardless of the default page size used |