diff mbox series

[RFC,5/5] x86: Build the core kernel with position independent codegen

Message ID 20240122090851.851120-12-ardb+git@google.com (mailing list archive)
State RFC
Headers show
Series x86: Build the core kernel using PIC codegen | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-VM_Test-3 success Logs for Validate matrix.py
bpf/vmtest-bpf-next-VM_Test-0 success Logs for Lint
bpf/vmtest-bpf-next-VM_Test-12 success Logs for s390x-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-4 success Logs for aarch64-gcc / build / build for aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-2 success Logs for Unittests
bpf/vmtest-bpf-next-VM_Test-10 success Logs for aarch64-gcc / veristat
bpf/vmtest-bpf-next-VM_Test-5 success Logs for aarch64-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-1 success Logs for ShellCheck
bpf/vmtest-bpf-next-VM_Test-6 success Logs for aarch64-gcc / test (test_maps, false, 360) / test_maps on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-11 success Logs for s390x-gcc / build / build for s390x with gcc
bpf/vmtest-bpf-next-VM_Test-8 success Logs for aarch64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-7 success Logs for aarch64-gcc / test (test_progs, false, 360) / test_progs on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-9 success Logs for aarch64-gcc / test (test_verifier, false, 360) / test_verifier on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-17 success Logs for s390x-gcc / veristat
bpf/vmtest-bpf-next-VM_Test-18 success Logs for set-matrix
bpf/vmtest-bpf-next-VM_Test-19 fail Logs for x86_64-gcc / build / build for x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-20 success Logs for x86_64-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-21 success Logs for x86_64-gcc / test
bpf/vmtest-bpf-next-VM_Test-22 success Logs for x86_64-gcc / veristat
bpf/vmtest-bpf-next-VM_Test-23 fail Logs for x86_64-llvm-17 / build / build for x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-24 fail Logs for x86_64-llvm-17 / build-release / build for x86_64 with llvm-17 and -O2 optimization
bpf/vmtest-bpf-next-VM_Test-26 success Logs for x86_64-llvm-17 / veristat
bpf/vmtest-bpf-next-VM_Test-25 success Logs for x86_64-llvm-17 / test
bpf/vmtest-bpf-next-VM_Test-27 fail Logs for x86_64-llvm-18 / build / build for x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-28 fail Logs for x86_64-llvm-18 / build-release / build for x86_64 with llvm-18 and -O2 optimization
bpf/vmtest-bpf-next-VM_Test-29 success Logs for x86_64-llvm-18 / test
bpf/vmtest-bpf-next-VM_Test-30 success Logs for x86_64-llvm-18 / veristat
bpf/vmtest-bpf-next-VM_Test-16 success Logs for s390x-gcc / test (test_verifier, false, 360) / test_verifier on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-14 success Logs for s390x-gcc / test (test_progs, false, 360) / test_progs on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-15 success Logs for s390x-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on s390x with gcc
bpf/vmtest-bpf-next-PR fail PR summary
bpf/vmtest-bpf-next-VM_Test-13 success Logs for s390x-gcc / test (test_maps, false, 360) / test_maps on s390x with gcc
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Guessed tree name to be net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1079 this patch: 1079
netdev/build_tools success Errors and warnings before: 2 this patch: 0
netdev/cc_maintainers success CCed 0 of 0 maintainers
netdev/build_clang success Errors and warnings before: 3359 this patch: 3358
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn fail Errors and warnings before: 19130 this patch: 18039
netdev/checkpatch warning CHECK: spaces preferred around that '*' (ctx:ExV) CHECK: spaces preferred around that '*' (ctx:VxB)
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Ard Biesheuvel Jan. 22, 2024, 9:08 a.m. UTC 
From: Ard Biesheuvel <ardb@kernel.org>

Pass the -fpie flag to the compiler when building objects that are
intended for the core kernel. This ensures that all implicit symbol
references are emitted using RIP-relative relocations, allowing the code
to be executed correctly even if it runs from a different virtual
address than the address it was linked/loaded/relocated to run at.

This is necessary to ensure that all C code that gets pulled in by the
early startup code runs correctly without the need for unpalatable hacks
in the code to force RIP-relative references.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/Makefile                 | 7 +++++--
 arch/x86/entry/vdso/Makefile      | 2 +-
 arch/x86/kernel/Makefile          | 4 ----
 arch/x86/realmode/rm/Makefile     | 1 +
 include/asm-generic/vmlinux.lds.h | 2 ++
 5 files changed, 9 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index bed0850d91b0..0382a9534099 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -165,11 +165,13 @@  else
         KBUILD_RUSTFLAGS += $(rustflags-y)
 
         KBUILD_CFLAGS += -mno-red-zone
-        KBUILD_CFLAGS += -mcmodel=kernel
+        KBUILD_CFLAGS_MODULE += -mcmodel=kernel
         KBUILD_RUSTFLAGS += -Cno-redzone=y
-        KBUILD_RUSTFLAGS += -Ccode-model=kernel
+        KBUILD_RUSTFLAGS_KERNEL += -Ccode-model=small
+        KBUILD_RUSTFLAGS_MODULE += -Ccode-model=kernel
 
 	PIE_CFLAGS := -fpie -mcmodel=small \
+		      $(call cc-option,-Wa$(comma)-mrelax-relocations=no) \
 		      -include $(srctree)/include/linux/hidden.h
 
 	ifeq ($(CONFIG_STACKPROTECTOR),y)
@@ -178,6 +180,7 @@  else
 		endif
 	endif
 
+	KBUILD_CFLAGS_KERNEL += $(PIE_CFLAGS)
 	export PIE_CFLAGS
 endif
 
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index b1b8dd1608f7..e2c79d4c1417 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -149,7 +149,7 @@  $(obj)/vdso32.so.dbg: KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
 $(obj)/vdso32.so.dbg: asflags-$(CONFIG_X86_64) += -m32
 
 KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS))
-KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32))
+KBUILD_CFLAGS_32 := $(filter-out -mcmodel=small,$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
 KBUILD_CFLAGS_32 := $(filter-out $(RANDSTRUCT_CFLAGS),$(KBUILD_CFLAGS_32))
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 65194ca79b5c..0000325ab98f 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -21,10 +21,6 @@  CFLAGS_REMOVE_sev.o = -pg
 CFLAGS_REMOVE_rethook.o = -pg
 endif
 
-# head64.c contains C code that may execute from a different virtual address
-# than it was linked at, so we always build it using PIE codegen
-CFLAGS_head64.o += $(PIE_CFLAGS)
-
 KASAN_SANITIZE_head$(BITS).o				:= n
 KASAN_SANITIZE_dumpstack.o				:= n
 KASAN_SANITIZE_dumpstack_$(BITS).o			:= n
diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile
index f614009d3e4e..fdb8e780f903 100644
--- a/arch/x86/realmode/rm/Makefile
+++ b/arch/x86/realmode/rm/Makefile
@@ -76,5 +76,6 @@  KBUILD_CFLAGS	:= $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \
 		   -I$(srctree)/arch/x86/boot
 KBUILD_AFLAGS	:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
 KBUILD_CFLAGS	+= -fno-asynchronous-unwind-tables
+KBUILD_CFLAGS_KERNEL := $(filter-out $(PIE_CFLAGS),$(KBUILD_CFLAGS_KERNEL))
 GCOV_PROFILE := n
 UBSAN_SANITIZE := n
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index ef45331fb043..9518b87207e8 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -355,6 +355,7 @@ 
 	*(.data..decrypted)						\
 	*(.ref.data)							\
 	*(.data..shared_aligned) /* percpu related */			\
+	*(.data.rel .data.rel.*)					\
 	MEM_KEEP(init.data*)						\
 	*(.data.unlikely)						\
 	__start_once = .;						\
@@ -477,6 +478,7 @@ 
 	.rodata           : AT(ADDR(.rodata) - LOAD_OFFSET) {		\
 		__start_rodata = .;					\
 		*(.rodata) *(.rodata.*)					\
+		*(.data.rel.ro*)					\
 		SCHED_DATA						\
 		RO_AFTER_INIT_DATA	/* Read only after init */	\
 		. = ALIGN(8);						\