| Message ID | 20171225205440.14575-2-ard.biesheuvel@linaro.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | add support for relative references in special sections | expand |
Hi Ard. On Mon, Dec 25, 2017 at 08:54:33PM +0000, Ard Biesheuvel wrote: > Before updating certain subsystems to use place relative 32-bit > relocations in special sections, to save space and reduce the > number of absolute relocations that need to be processed at runtime > by relocatable kernels, introduce the Kconfig symbol and define it > for some architectures that should be able to support and benefit > from it. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> > Cc: Heiko Carstens <heiko.carstens@de.ibm.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: x86@kernel.org > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > --- > arch/Kconfig | 10 ++++++++++ > arch/arm64/Kconfig | 1 + > arch/arm64/kernel/vmlinux.lds.S | 2 +- The change to arch/arm64/kernel/vmlinux.lds.S is not justified in the changelog. Did you add it by mistake? Sam
On 25 December 2017 at 21:05, Sam Ravnborg <sam@ravnborg.org> wrote: > Hi Ard. > > On Mon, Dec 25, 2017 at 08:54:33PM +0000, Ard Biesheuvel wrote: >> Before updating certain subsystems to use place relative 32-bit >> relocations in special sections, to save space and reduce the >> number of absolute relocations that need to be processed at runtime >> by relocatable kernels, introduce the Kconfig symbol and define it >> for some architectures that should be able to support and benefit >> from it. >> >> Cc: Catalin Marinas <catalin.marinas@arm.com> >> Cc: Will Deacon <will.deacon@arm.com> >> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> >> Cc: Paul Mackerras <paulus@samba.org> >> Cc: Michael Ellerman <mpe@ellerman.id.au> >> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> >> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> >> Cc: Thomas Gleixner <tglx@linutronix.de> >> Cc: Ingo Molnar <mingo@redhat.com> >> Cc: "H. Peter Anvin" <hpa@zytor.com> >> Cc: x86@kernel.org >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >> --- >> arch/Kconfig | 10 ++++++++++ >> arch/arm64/Kconfig | 1 + > >> arch/arm64/kernel/vmlinux.lds.S | 2 +- > The change to arch/arm64/kernel/vmlinux.lds.S is > not justified in the changelog. > Did you add it by mistake? > No. The PREL32 support adds a __ADDRESSABLE() macro that emits code into .discard.text, and on arm64, the EFI object sections get a .init prefix so we need to discard .init.discard.* explicitly as well. I will add this as a note. Thanks, Ard.
diff --git a/arch/Kconfig b/arch/Kconfig index 400b9e1b2f27..dbc036a7bd1b 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -959,4 +959,14 @@ config REFCOUNT_FULL against various use-after-free conditions that can be used in security flaw exploits. +config HAVE_ARCH_PREL32_RELOCATIONS + bool + help + May be selected by an architecture if it supports place-relative + 32-bit relocations, both in the toolchain and in the module loader, + in which case relative references can be used in special sections + for PCI fixup, initcalls etc which are only half the size on 64 bit + architectures, and don't require runtime relocation on relocatable + kernels. + source "kernel/gcov/Kconfig" diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index c9a7e9e1414f..66c7b9ab2a3d 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -89,6 +89,7 @@ config ARM64 select HAVE_ARCH_KGDB select HAVE_ARCH_MMAP_RND_BITS select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT + select HAVE_ARCH_PREL32_RELOCATIONS select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_TRACEHOOK select HAVE_ARCH_TRANSPARENT_HUGEPAGE diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 7da3e5c366a0..49ae5b43fe2b 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -156,7 +156,7 @@ SECTIONS CON_INITCALL SECURITY_INITCALL INIT_RAM_FS - *(.init.rodata.* .init.bss) /* from the EFI stub */ + *(.init.rodata.* .init.bss .init.discard.*) /* EFI stub */ } .exit.data : { ARM_EXIT_KEEP(EXIT_DATA) diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index c51e6ce42e7a..e172478e2ae7 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -177,6 +177,7 @@ config PPC select HAVE_ARCH_KGDB select HAVE_ARCH_MMAP_RND_BITS select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT + select HAVE_ARCH_PREL32_RELOCATIONS select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_TRACEHOOK select ARCH_HAS_STRICT_KERNEL_RWX if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION) diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 829c67986db7..ed29d1ebecd9 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -129,6 +129,7 @@ config S390 select HAVE_ARCH_AUDITSYSCALL select HAVE_ARCH_JUMP_LABEL select CPU_NO_EFFICIENT_FFS if !HAVE_MARCH_Z9_109_FEATURES + select HAVE_ARCH_PREL32_RELOCATIONS select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_SOFT_DIRTY select HAVE_ARCH_TRACEHOOK diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index d4fc98c50378..9f2bb853aedb 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -115,6 +115,7 @@ config X86 select HAVE_ARCH_MMAP_RND_BITS if MMU select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT + select HAVE_ARCH_PREL32_RELOCATIONS select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_TRACEHOOK select HAVE_ARCH_TRANSPARENT_HUGEPAGE
Before updating certain subsystems to use place relative 32-bit relocations in special sections, to save space and reduce the number of absolute relocations that need to be processed at runtime by relocatable kernels, introduce the Kconfig symbol and define it for some architectures that should be able to support and benefit from it. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/Kconfig | 10 ++++++++++ arch/arm64/Kconfig | 1 + arch/arm64/kernel/vmlinux.lds.S | 2 +- arch/powerpc/Kconfig | 1 + arch/s390/Kconfig | 1 + arch/x86/Kconfig | 1 + 6 files changed, 15 insertions(+), 1 deletion(-)