On Mon, 11 Jan, at 02:19:15PM, Ard Biesheuvel wrote: > Since arm64 does not use a decompressor that supplies an execution > environment where it is feasible to some extent to provide a source of > randomness, the arm64 KASLR kernel depends on the bootloader to supply > some random bits in register x1 upon kernel entry. > > On UEFI systems, we can use the EFI_RNG_PROTOCOL, if supplied, to obtain > some random bits. At the same time, use it to randomize the offset of the > kernel Image in physical memory. > > Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org> > --- > arch/arm64/Kconfig | 5 ++ > arch/arm64/kernel/efi-entry.S | 7 +- > drivers/firmware/efi/libstub/arm-stub.c | 17 ++--- > drivers/firmware/efi/libstub/arm64-stub.c | 67 +++++++++++++++----- > drivers/firmware/efi/libstub/efi-stub-helper.c | 10 +++ > drivers/firmware/efi/libstub/efistub.h | 2 + > 6 files changed, 82 insertions(+), 26 deletions(-)
[...] > diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c > b/drivers/firmware/efi/libstub/efi-stub-helper.c > index 2a7a3015d7e0..e8a3b8cd53cc 100644 > --- a/drivers/firmware/efi/libstub/efi-stub-helper.c > +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c > @@ -32,6 +32,10 @@ > > static unsigned long __chunk_size = EFI_READ_CHUNK_SIZE; > > +#ifdef CONFIG_RANDOMIZE_BASE > +bool __nokaslr; > +#endif > + > /* > * Allow the platform to override the allocation granularity: this allows > * systems that have the capability to run with a larger page size to deal > @@ -317,6 +321,12 @@ efi_status_t efi_parse_options(char *cmdline) > { > char *str; > > +#ifdef CONFIG_RANDOMIZE_BASE > + str = strstr(cmdline, "nokaslr"); > + if (str && (str == cmdline || *(str - 1) == ' ')) > + __nokaslr = true; > +#endif > + > /* > * If no EFI parameters were specified on the cmdline we've got > * nothing to do. Could we not keep the "nokaslr" parsing inside of arm-stub.c? It's not really specific to EFI and doesn't make use of any of the code in efi_parse_options() anyhow. As an added bonus, __nokaslr could then become static.