From 7c936d8bcf8105518a924d335658ae2cee8bcbc3 Mon Sep 17 00:00:00 2001 From: Arvind Sankar Date: Tue, 14 Jul 2020 20:41:33 -0400 Subject: [PATCH] FROMLIST: x86/boot: Check that there are no run-time relocations Add a linker script check that there are no run-time relocations, and remove the old one that tries to check via looking for specially-named sections in the object files. Drop the tests for -fPIE compiler option and -pie linker option, as they are available in all supported gcc and binutils versions (as well as clang and lld). Reviewed-by: Kees Cook Reviewed-by: Ard Biesheuvel Reviewed-by: Fangrui Song Signed-off-by: Arvind Sankar Link: https://lore.kernel.org/lkml/20200629140928.858507-8-nivedita@alum.mit.edu Bug: 167402429 Signed-off-by: Alistair Delva Change-Id: I13a1e5a3292e3b4fb054e1489f269964a31428e9 --- arch/x86/boot/compressed/Makefile | 26 ++------------------------ arch/x86/boot/compressed/vmlinux.lds.S | 8 ++++++++ 2 files changed, 10 insertions(+), 24 deletions(-) diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 2c5afeeade46..c7e9adbf7573 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -52,7 +52,7 @@ UBSAN_SANITIZE :=n KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE) # Compressed kernel should be built as PIE since it may be loaded at any # address by the bootloader. -LDFLAGS_vmlinux := $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker) +LDFLAGS_vmlinux := -pie $(call ld-option, --no-dynamic-linker) LDFLAGS_vmlinux += -T hostprogs := mkpiggy @@ -87,30 +87,8 @@ vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o efi-obj-$(CONFIG_EFI_STUB) = $(objtree)/drivers/firmware/efi/libstub/lib.a -# The compressed kernel is built with -fPIC/-fPIE so that a boot loader -# can place it anywhere in memory and it will still run. However, since -# it is executed as-is without any ELF relocation processing performed -# (and has already had all relocation sections stripped from the binary), -# none of the code can use data relocations (e.g. static assignments of -# pointer values), since they will be meaningless at runtime. This check -# will refuse to link the vmlinux if any of these relocations are found. -quiet_cmd_check_data_rel = DATAREL $@ -define cmd_check_data_rel - for obj in $(filter %.o,$^); do \ - $(READELF) -S $$obj | grep -qF .rel.local && { \ - echo "error: $$obj has data relocations!" >&2; \ - exit 1; \ - } || true; \ - done -endef - -# We need to run two commands under "if_changed", so merge them into a -# single invocation. -quiet_cmd_check-and-link-vmlinux = LD $@ - cmd_check-and-link-vmlinux = $(cmd_check_data_rel); $(cmd_ld) - $(obj)/vmlinux: $(vmlinux-objs-y) $(efi-obj-y) FORCE - $(call if_changed,check-and-link-vmlinux) + $(call if_changed,ld) OBJCOPYFLAGS_vmlinux.bin := -R .comment -S $(obj)/vmlinux.bin: vmlinux FORCE diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S index a4a4a59a2628..29df99b6cc64 100644 --- a/arch/x86/boot/compressed/vmlinux.lds.S +++ b/arch/x86/boot/compressed/vmlinux.lds.S @@ -42,6 +42,12 @@ SECTIONS *(.rodata.*) _erodata = . ; } + .rel.dyn : { + *(.rel.*) + } + .rela.dyn : { + *(.rela.*) + } .got : { *(.got) } @@ -85,3 +91,5 @@ ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected GOT/PLT en #else ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0xc, "Unexpected GOT/PLT entries detected!") #endif + +ASSERT(SIZEOF(.rel.dyn) == 0 && SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations detected!")