| Message ID | 20200615101939.634391-1-ardb@kernel.org (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 751c263bb74fd36b5fc2589d36abc75042336444 |
| Headers | show |
| Series | arm64: remove TEXT_OFFSET randomization | expand |
On Mon, Jun 15, 2020 at 12:19:39PM +0200, Ard Biesheuvel wrote: > TEXT_OFFSET was recently changed to 0x0, in preparation for its removal > at a later stage, and a warning is emitted into the kernel log when the > bootloader appears to have failed to take the TEXT_OFFSET image header > value into account. > > Ironically, this warning itself fails to take TEXT_OFFSET into account, > and compares the kernel image's alignment modulo 2M against a hardcoded > value of 0x0, and so the warning will trigger spuriously when TEXT_OFFSET > randomization is enabled. > > Given the intent to get rid of TEXT_OFFSET entirely, let's fix this > oversight by just removing support for TEXT_OFFSET randomization. > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> If nothing else, it's nice to see the scary awk go, so: Acked-by: Mark Rutland <mark.rutland@arm.com> Mark. > --- > arch/arm64/Kconfig.debug | 15 --------------- > arch/arm64/Makefile | 6 ------ > 2 files changed, 21 deletions(-) > > diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug > index cdf7ec0b975e..265c4461031f 100644 > --- a/arch/arm64/Kconfig.debug > +++ b/arch/arm64/Kconfig.debug > @@ -8,21 +8,6 @@ config PID_IN_CONTEXTIDR > instructions during context switch. Say Y here only if you are > planning to use hardware trace tools with this kernel. > > -config ARM64_RANDOMIZE_TEXT_OFFSET > - bool "Randomize TEXT_OFFSET at build time" > - help > - Say Y here if you want the image load offset (AKA TEXT_OFFSET) > - of the kernel to be randomized at build-time. When selected, > - this option will cause TEXT_OFFSET to be randomized upon any > - build of the kernel, and the offset will be reflected in the > - text_offset field of the resulting Image. This can be used to > - fuzz-test bootloaders which respect text_offset. > - > - This option is intended for bootloader and/or kernel testing > - only. Bootloaders must make no assumptions regarding the value > - of TEXT_OFFSET and platforms must not require a specific > - value. > - > config DEBUG_EFI > depends on EFI && DEBUG_INFO > bool "UEFI debugging" > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index 76359cfb328a..a0d94d063fa8 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile > @@ -121,13 +121,7 @@ endif > head-y := arch/arm64/kernel/head.o > > # The byte offset of the kernel image in RAM from the start of RAM. > -ifeq ($(CONFIG_ARM64_RANDOMIZE_TEXT_OFFSET), y) > -TEXT_OFFSET := $(shell awk "BEGIN {srand(); printf \"0x%06x\n\", \ > - int(2 * 1024 * 1024 / (2 ^ $(CONFIG_ARM64_PAGE_SHIFT)) * \ > - rand()) * (2 ^ $(CONFIG_ARM64_PAGE_SHIFT))}") > -else > TEXT_OFFSET := 0x0 > -endif > > ifeq ($(CONFIG_KASAN_SW_TAGS), y) > KASAN_SHADOW_SCALE_SHIFT := 4 > -- > 2.27.0 >
On Mon, 15 Jun 2020 12:19:39 +0200, Ard Biesheuvel wrote: > TEXT_OFFSET was recently changed to 0x0, in preparation for its removal > at a later stage, and a warning is emitted into the kernel log when the > bootloader appears to have failed to take the TEXT_OFFSET image header > value into account. > > Ironically, this warning itself fails to take TEXT_OFFSET into account, > and compares the kernel image's alignment modulo 2M against a hardcoded > value of 0x0, and so the warning will trigger spuriously when TEXT_OFFSET > randomization is enabled. > > [...] Applied to arm64 (for-next/fixes), thanks! [1/1] arm64: remove TEXT_OFFSET randomization https://git.kernel.org/arm64/c/751c263bb74f Cheers,
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug index cdf7ec0b975e..265c4461031f 100644 --- a/arch/arm64/Kconfig.debug +++ b/arch/arm64/Kconfig.debug @@ -8,21 +8,6 @@ config PID_IN_CONTEXTIDR instructions during context switch. Say Y here only if you are planning to use hardware trace tools with this kernel. -config ARM64_RANDOMIZE_TEXT_OFFSET - bool "Randomize TEXT_OFFSET at build time" - help - Say Y here if you want the image load offset (AKA TEXT_OFFSET) - of the kernel to be randomized at build-time. When selected, - this option will cause TEXT_OFFSET to be randomized upon any - build of the kernel, and the offset will be reflected in the - text_offset field of the resulting Image. This can be used to - fuzz-test bootloaders which respect text_offset. - - This option is intended for bootloader and/or kernel testing - only. Bootloaders must make no assumptions regarding the value - of TEXT_OFFSET and platforms must not require a specific - value. - config DEBUG_EFI depends on EFI && DEBUG_INFO bool "UEFI debugging" diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 76359cfb328a..a0d94d063fa8 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -121,13 +121,7 @@ endif head-y := arch/arm64/kernel/head.o # The byte offset of the kernel image in RAM from the start of RAM. -ifeq ($(CONFIG_ARM64_RANDOMIZE_TEXT_OFFSET), y) -TEXT_OFFSET := $(shell awk "BEGIN {srand(); printf \"0x%06x\n\", \ - int(2 * 1024 * 1024 / (2 ^ $(CONFIG_ARM64_PAGE_SHIFT)) * \ - rand()) * (2 ^ $(CONFIG_ARM64_PAGE_SHIFT))}") -else TEXT_OFFSET := 0x0 -endif ifeq ($(CONFIG_KASAN_SW_TAGS), y) KASAN_SHADOW_SCALE_SHIFT := 4
TEXT_OFFSET was recently changed to 0x0, in preparation for its removal at a later stage, and a warning is emitted into the kernel log when the bootloader appears to have failed to take the TEXT_OFFSET image header value into account. Ironically, this warning itself fails to take TEXT_OFFSET into account, and compares the kernel image's alignment modulo 2M against a hardcoded value of 0x0, and so the warning will trigger spuriously when TEXT_OFFSET randomization is enabled. Given the intent to get rid of TEXT_OFFSET entirely, let's fix this oversight by just removing support for TEXT_OFFSET randomization. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- arch/arm64/Kconfig.debug | 15 --------------- arch/arm64/Makefile | 6 ------ 2 files changed, 21 deletions(-)