Unverified Commit 310c33dc authored by Palmer Dabbelt's avatar Palmer Dabbelt
Browse files

Merge patch series "Introduce 64b relocatable kernel" 

Alexandre Ghiti <alexghiti@rivosinc.com> says:

After multiple attempts, this patchset is now based on the fact that the
64b kernel mapping was moved outside the linear mapping.

The first patch allows to build relocatable kernels but is not selected
by default. That patch is a requirement for KASLR.
The second and third patches take advantage of an already existing powerpc
script that checks relocations at compile-time, and uses it for riscv.

* b4-shazam-merge:
  riscv: Use --emit-relocs in order to move .rela.dyn in init
  riscv: Check relocations at compile time
  powerpc: Move script to check relocations at compile time in scripts/
  riscv: Introduce CONFIG_RELOCATABLE
  riscv: Move .rela.dyn outside of init to avoid empty relocations
  riscv: Prepare EFI header for relocatable kernels

Link: https://lore.kernel.org/r/20230329045329.64565-1-alexghiti@rivosinc.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parents 2667e367 559d1e45

arch/powerpc/tools/relocs_check.sh

+2 −16
Original line number Diff line number Diff line
@@ -15,21 +15,8 @@ if [ $# -lt 3 ]; then 
	exit 1

fi



# Have Kbuild supply the path to objdump and nm so we handle cross compilation.

objdump="$1"

nm="$2"

vmlinux="$3"



# Remove from the bad relocations those that match an undefined weak symbol

# which will result in an absolute relocation to 0.

# Weak unresolved symbols are of that form in nm output:

# "                  w _binary__btf_vmlinux_bin_end"

undef_weak_symbols=$($nm "$vmlinux" | awk '$1 ~ /w/ { print $2 }')



bad_relocs=$(

$objdump -R "$vmlinux" |

	# Only look at relocation lines.

	grep -E '\<R_' |

${srctree}/scripts/relocs_check.sh "$@" |

	# These relocations are okay

	# On PPC64:

	#	R_PPC64_RELATIVE, R_PPC64_NONE
@@ -44,8 +31,7 @@ R_PPC_ADDR16_LO 
R_PPC_ADDR16_HI

R_PPC_ADDR16_HA

R_PPC_RELATIVE

R_PPC_NONE' |

	([ "$undef_weak_symbols" ] && grep -F -w -v "$undef_weak_symbols" || cat)

R_PPC_NONE'

)



if [ -z "$bad_relocs" ]; then

arch/riscv/Kconfig

+14 −0
Original line number Diff line number Diff line
@@ -603,6 +603,20 @@ config COMPAT 


	  If you want to execute 32-bit userspace applications, say Y.



config RELOCATABLE

	bool "Build a relocatable kernel"

	depends on MMU && 64BIT && !XIP_KERNEL

	help

          This builds a kernel as a Position Independent Executable (PIE),

          which retains all relocation metadata required to relocate the

          kernel binary at runtime to a different virtual address than the

          address it was linked at.

          Since RISCV uses the RELA relocation format, this requires a

          relocation pass at runtime even if the kernel is loaded at the

          same address it was linked at.



          If unsure, say N.



endmenu # "Kernel features"



menu "Boot options"

arch/riscv/Makefile

+5 −2
Original line number Diff line number Diff line
@@ -7,9 +7,12 @@ 
#



OBJCOPYFLAGS    := -O binary

LDFLAGS_vmlinux :=

ifeq ($(CONFIG_RELOCATABLE),y)

	LDFLAGS_vmlinux += -shared -Bsymbolic -z notext -z norelro --emit-relocs

	KBUILD_CFLAGS += -fPIE

endif

ifeq ($(CONFIG_DYNAMIC_FTRACE),y)

	LDFLAGS_vmlinux := --no-relax

	LDFLAGS_vmlinux += --no-relax

	KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY

ifeq ($(CONFIG_RISCV_ISA_C),y)

	CC_FLAGS_FTRACE := -fpatchable-function-entry=4

arch/riscv/Makefile.postlink

0 → 100644
+49 −0
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0

# ===========================================================================

# Post-link riscv pass

# ===========================================================================

#

# Check that vmlinux relocations look sane



PHONY := __archpost

__archpost:



-include include/config/auto.conf

include $(srctree)/scripts/Kbuild.include



quiet_cmd_relocs_check = CHKREL  $@

cmd_relocs_check = 							\

	$(CONFIG_SHELL) $(srctree)/arch/riscv/tools/relocs_check.sh "$(OBJDUMP)" "$(NM)" "$@"



ifdef CONFIG_RELOCATABLE

quiet_cmd_cp_vmlinux_relocs = CPREL   vmlinux.relocs

cmd_cp_vmlinux_relocs = cp vmlinux vmlinux.relocs



quiet_cmd_relocs_strip = STRIPREL $@

cmd_relocs_strip = $(OBJCOPY)   --remove-section='.rel.*'       \

                                --remove-section='.rel__*'      \

                                --remove-section='.rela.*'      \

                                --remove-section='.rela__*' $@

endif



# `@true` prevents complaint when there is nothing to be done



vmlinux: FORCE

	@true

ifdef CONFIG_RELOCATABLE

	$(call if_changed,relocs_check)

	$(call if_changed,cp_vmlinux_relocs)

	$(call if_changed,relocs_strip)

endif



%.ko: FORCE

	@true



clean:

	@true



PHONY += FORCE clean



FORCE:



.PHONY: $(PHONY)

arch/riscv/boot/Makefile

+7 −0
Original line number Diff line number Diff line
@@ -33,7 +33,14 @@ $(obj)/xipImage: vmlinux FORCE 


endif



ifdef CONFIG_RELOCATABLE

vmlinux.relocs: vmlinux

	@ (! [ -f vmlinux.relocs ] && echo "vmlinux.relocs can't be found, please remove vmlinux and try again") || true



$(obj)/Image: vmlinux.relocs FORCE

else

$(obj)/Image: vmlinux FORCE

endif

	$(call if_changed,objcopy)



$(obj)/Image.gz: $(obj)/Image FORCE