On Thu, Nov 15, 2018 at 02:52:55PM +0900, AKASHI Takahiro wrote: > Adding "kaslr-seed" to dtb enables triggering kaslr, or kernel virtual > address randomization, at secondary kernel boot. We always do this as > it will have no harm on kaslr-incapable kernel. > > We don't have any "switch" to turn off this feature directly, but still > can suppress it by passing "nokaslr" as a kernel boot argument. > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: Will Deacon <will.deacon@xxxxxxx> > --- > arch/arm64/kernel/machine_kexec_file.c | 46 +++++++++++++++++++++++++- > 1 file changed, 45 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c > index ab296b98d633..a0a730bd9be6 100644 > --- a/arch/arm64/kernel/machine_kexec_file.c > +++ b/arch/arm64/kernel/machine_kexec_file.c > @@ -16,6 +16,7 @@ > #include <linux/libfdt.h> > #include <linux/memblock.h> > #include <linux/of_fdt.h> > +#include <linux/random.h> > #include <linux/slab.h> > #include <linux/string.h> > #include <linux/types.h> > @@ -28,6 +29,7 @@ > #define FDT_PSTR_INITRD_STA "linux,initrd-start" > #define FDT_PSTR_INITRD_END "linux,initrd-end" > #define FDT_PSTR_BOOTARGS "bootargs" > +#define FDT_PSTR_KASLR_SEED "kaslr-seed" > > const struct kexec_file_ops * const kexec_file_loaders[] = { > &kexec_image_ops, > @@ -46,11 +48,38 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image) > return kexec_image_post_load_cleanup_default(image); > } > > +/* crng needs to have been initialized for providing kaslr-seed */ > +static int random_ready; > + > +static void random_ready_notified(struct random_ready_callback *unused) > +{ > + random_ready = 1; > +} > + > +static struct random_ready_callback random_ready_cb = { > + .func = random_ready_notified, > +}; > + > +static __init int init_random_ready_cb(void) > +{ > + int ret; > + > + ret = add_random_ready_callback(&random_ready_cb); > + if (ret == -EALREADY) > + random_ready = 1; > + else if (ret) > + pr_warn("failed to add a callback for random_ready\n"); > + > + return 0; > +} > +late_initcall(init_random_ready_cb) Why can't we just call crng_ready()? > + > static int setup_dtb(struct kimage *image, > unsigned long initrd_load_addr, unsigned long initrd_len, > char *cmdline, void *dtb) > { > int nodeoffset; > + u64 value; > int ret; > > nodeoffset = fdt_path_offset(dtb, "/chosen"); > @@ -106,12 +135,27 @@ static int setup_dtb(struct kimage *image, > return -EINVAL; > } > > + /* add kaslr-seed */ > + ret = fdt_delprop(dtb, nodeoffset, FDT_PSTR_KASLR_SEED); > + if (ret && (ret != -FDT_ERR_NOTFOUND)) > + return -EINVAL; > + > + if (random_ready) { > + get_random_bytes(&value, sizeof(value)); get_random_u64() ? > + ret = fdt_setprop_u64(dtb, nodeoffset, FDT_PSTR_KASLR_SEED, > + value); > + if (ret) > + return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL); > + } else { Wouldn't we be better off preserving the previous seed here, if it was present? > + pr_notice("kaslr-seed won't be fed\n"); "fed" is probably not the right word here. Will _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec