| Message ID | 1456938712-11089-3-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
On 2 March 2016 at 18:11, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > Since KASLR requires a relocatable kernel image anyway, there is no > practical reason to refuse an image whose load address is not exactly > TEXT_OFFSET bytes above a 2 MB aligned base address, as long as the > physical and virtual misalignment with respect to the swapper block > size are equal. So treat the misalignment of the physical load address > as the initial KASLR offset, and fix up the remaining code to deal with > that. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > --- > arch/arm64/kernel/head.S | 16 ++++++++++++---- > arch/arm64/kernel/kaslr.c | 6 +++--- > 2 files changed, 15 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 1d4ae36db0bb..934d6dcd7a57 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -25,6 +25,7 @@ > #include <linux/irqchip/arm-gic-v3.h> > > #include <asm/assembler.h> > +#include <asm/boot.h> > #include <asm/ptrace.h> > #include <asm/asm-offsets.h> > #include <asm/cache.h> > @@ -211,8 +212,12 @@ section_table: > ENTRY(stext) > bl preserve_boot_args > bl el2_setup // Drop to EL1, w20=cpu_boot_mode > - mov x23, xzr // KASLR offset, defaults to 0 > adrp x24, __PHYS_OFFSET > +#ifdef CONFIG_RANDOMIZE_BASE This should be ifndef. (I moved this around right before posting, but failed to invert the condition) > + mov x23, xzr // KASLR offset, defaults to 0 > +#else > + and x23, x24, MIN_KIMG_ALIGN - 1 // unless loaded phys misaligned > +#endif > bl set_cpu_boot_mode_flag > bl __create_page_tables // x25=TTBR0, x26=TTBR1 > /* > @@ -489,11 +494,13 @@ __mmap_switched: > bl kasan_early_init > #endif > #ifdef CONFIG_RANDOMIZE_BASE > - cbnz x23, 0f // already running randomized? > + tst x23, ~(MIN_KIMG_ALIGN - 1) // already running randomized? > + b.ne 0f > mov x0, x21 // pass FDT address in x0 > + mov x1, x23 // pass modulo offset in x1 > bl kaslr_early_init // parse FDT for KASLR options > cbz x0, 0f // KASLR disabled? just proceed > - mov x23, x0 // record KASLR offset > + orr x23, x23, x0 // record KASLR offset > ret x28 // we must enable KASLR, return > // to __enable_mmu() > 0: > @@ -753,7 +760,8 @@ __enable_mmu: > isb > #ifdef CONFIG_RANDOMIZE_BASE > mov x19, x0 // preserve new SCTLR_EL1 value > - blr x27 > + add x30, x27, x23 > + blr x30 > > /* > * If we return here, we have a KASLR displacement in x23 which we need > diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c > index 582983920054..b05469173ba5 100644 > --- a/arch/arm64/kernel/kaslr.c > +++ b/arch/arm64/kernel/kaslr.c > @@ -74,7 +74,7 @@ extern void *__init __fixmap_remap_fdt(phys_addr_t dt_phys, int *size, > * containing function pointers) to be reinitialized, and zero-initialized > * .bss variables will be reset to 0. > */ > -u64 __init kaslr_early_init(u64 dt_phys) > +u64 __init kaslr_early_init(u64 dt_phys, u64 modulo_offset) > { > void *fdt; > u64 seed, offset, mask, module_range; > @@ -132,8 +132,8 @@ u64 __init kaslr_early_init(u64 dt_phys) > * boundary (for 4KB/16KB/64KB granule kernels, respectively). If this > * happens, increase the KASLR offset by the size of the kernel image. > */ > - if ((((u64)_text + offset) >> SWAPPER_TABLE_SHIFT) != > - (((u64)_end + offset) >> SWAPPER_TABLE_SHIFT)) > + if ((((u64)_text + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT) != > + (((u64)_end + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT)) > offset = (offset + (u64)(_end - _text)) & mask; > > if (IS_ENABLED(CONFIG_KASAN)) > -- > 2.5.0 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 1d4ae36db0bb..934d6dcd7a57 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -25,6 +25,7 @@ #include <linux/irqchip/arm-gic-v3.h> #include <asm/assembler.h> +#include <asm/boot.h> #include <asm/ptrace.h> #include <asm/asm-offsets.h> #include <asm/cache.h> @@ -211,8 +212,12 @@ section_table: ENTRY(stext) bl preserve_boot_args bl el2_setup // Drop to EL1, w20=cpu_boot_mode - mov x23, xzr // KASLR offset, defaults to 0 adrp x24, __PHYS_OFFSET +#ifdef CONFIG_RANDOMIZE_BASE + mov x23, xzr // KASLR offset, defaults to 0 +#else + and x23, x24, MIN_KIMG_ALIGN - 1 // unless loaded phys misaligned +#endif bl set_cpu_boot_mode_flag bl __create_page_tables // x25=TTBR0, x26=TTBR1 /* @@ -489,11 +494,13 @@ __mmap_switched: bl kasan_early_init #endif #ifdef CONFIG_RANDOMIZE_BASE - cbnz x23, 0f // already running randomized? + tst x23, ~(MIN_KIMG_ALIGN - 1) // already running randomized? + b.ne 0f mov x0, x21 // pass FDT address in x0 + mov x1, x23 // pass modulo offset in x1 bl kaslr_early_init // parse FDT for KASLR options cbz x0, 0f // KASLR disabled? just proceed - mov x23, x0 // record KASLR offset + orr x23, x23, x0 // record KASLR offset ret x28 // we must enable KASLR, return // to __enable_mmu() 0: @@ -753,7 +760,8 @@ __enable_mmu: isb #ifdef CONFIG_RANDOMIZE_BASE mov x19, x0 // preserve new SCTLR_EL1 value - blr x27 + add x30, x27, x23 + blr x30 /* * If we return here, we have a KASLR displacement in x23 which we need diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c index 582983920054..b05469173ba5 100644 --- a/arch/arm64/kernel/kaslr.c +++ b/arch/arm64/kernel/kaslr.c @@ -74,7 +74,7 @@ extern void *__init __fixmap_remap_fdt(phys_addr_t dt_phys, int *size, * containing function pointers) to be reinitialized, and zero-initialized * .bss variables will be reset to 0. */ -u64 __init kaslr_early_init(u64 dt_phys) +u64 __init kaslr_early_init(u64 dt_phys, u64 modulo_offset) { void *fdt; u64 seed, offset, mask, module_range; @@ -132,8 +132,8 @@ u64 __init kaslr_early_init(u64 dt_phys) * boundary (for 4KB/16KB/64KB granule kernels, respectively). If this * happens, increase the KASLR offset by the size of the kernel image. */ - if ((((u64)_text + offset) >> SWAPPER_TABLE_SHIFT) != - (((u64)_end + offset) >> SWAPPER_TABLE_SHIFT)) + if ((((u64)_text + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT) != + (((u64)_end + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT)) offset = (offset + (u64)(_end - _text)) & mask; if (IS_ENABLED(CONFIG_KASAN))
Since KASLR requires a relocatable kernel image anyway, there is no practical reason to refuse an image whose load address is not exactly TEXT_OFFSET bytes above a 2 MB aligned base address, as long as the physical and virtual misalignment with respect to the swapper block size are equal. So treat the misalignment of the physical load address as the initial KASLR offset, and fix up the remaining code to deal with that. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/kernel/head.S | 16 ++++++++++++---- arch/arm64/kernel/kaslr.c | 6 +++--- 2 files changed, 15 insertions(+), 7 deletions(-) -- 2.5.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel