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2f97967503
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James Morse 2f97967503 arm64: kpti: Update arm64_kernel_use_ng_mappings() when forced on 
Since commit b89d82ef01 ("arm64: kpti: Avoid rewriting early page
tables when KASLR is enabled"), a kernel built with CONFIG_RANDOMIZE_BASE
can decide early whether to use non-global mappings by checking the
kaslr_offset().

A kernel built without CONFIG_RANDOMIZE_BASE, instead checks the
cpufeature static-key.

This leaves a gap where CONFIG_RANDOMIZE_BASE was enabled, no
kaslr seed was provided, but kpti was forced on using the cmdline
option.

When the decision is made late, kpti_install_ng_mappings() will re-write
the page tables, but arm64_kernel_use_ng_mappings()'s value does not
change as it only tests the cpufeature static-key if
CONFIG_RANDOMIZE_BASE is disabled.
This function influences PROT_DEFAULT via PTE_MAYBE_NG, and causes
pgattr_change_is_safe() to catch nG->G transitions when the unchanged
PROT_DEFAULT is used as part of PAGE_KERNEL_RO:
[    1.942255] alternatives: patching kernel code
[    1.998288] ------------[ cut here ]------------
[    2.000693] kernel BUG at arch/arm64/mm/mmu.c:165!
[    2.019215] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[    2.020257] Modules linked in:
[    2.020807] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc2 #51
[    2.021917] Hardware name: linux,dummy-virt (DT)
[    2.022790] pstate: 40000005 (nZcv daif -PAN -UAO)
[    2.023742] pc : __create_pgd_mapping+0x508/0x6d0
[    2.024671] lr : __create_pgd_mapping+0x500/0x6d0

[    2.058059] Process swapper/0 (pid: 1, stack limit = 0x(____ptrval____))
[    2.059369] Call trace:
[    2.059845]  __create_pgd_mapping+0x508/0x6d0
[    2.060684]  update_mapping_prot+0x48/0xd0
[    2.061477]  mark_linear_text_alias_ro+0xdc/0xe4
[    2.070502]  smp_cpus_done+0x90/0x98
[    2.071216]  smp_init+0x100/0x114
[    2.071878]  kernel_init_freeable+0xd4/0x220
[    2.072750]  kernel_init+0x10/0x100
[    2.073455]  ret_from_fork+0x10/0x18

[    2.075414] ---[ end trace 3572f3a7782292de ]---
[    2.076389] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b

If arm64_kernel_unmapped_at_el0() is true, arm64_kernel_use_ng_mappings()
should also be true.

Signed-off-by: James Morse <james.morse@arm.com>
CC: Ard Biesheuvel <ard.biesheuvel@linaro.org>
CC: John Garry <john.garry@huawei.com>
CC: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2019-01-16 11:55:11 +00:00
..
boot arm64: dts: marvell: mcbin: fix PCIe reset signal 2019-01-10 12:20:32 +01:00
configs arm64: defconfig: enable modules for amlogic s400 sound card 2019-01-08 15:27:50 -08:00
crypto Kbuild updates for v4.21 2018-12-29 12:03:17 -08:00
include arm64: kpti: Update arm64_kernel_use_ng_mappings() when forced on 2019-01-16 11:55:11 +00:00
kernel arm64: kexec_file: return successfully even if kaslr-seed doesn't exist 2019-01-11 10:10:51 +00:00
kvm Kconfig updates for v4.21 2018-12-29 13:03:29 -08:00
lib arm64: string: use asm EXPORT_SYMBOL() 2018-12-10 11:50:12 +00:00
mm arm64 fixes for -rc1 2019-01-05 11:28:39 -08:00
net bpf: arm64: Enable arm64 jit to provide bpf_line_info 2018-12-12 02:16:56 +01:00
xen
Kconfig Kconfig file consolidation for v4.21 2018-12-29 13:40:29 -08:00
Kconfig.debug Kconfig: consolidate the "Kernel hacking" menu 2018-08-02 08:06:48 +09:00
Kconfig.platforms ARM: SoC: late updates 2019-01-05 11:30:37 -08:00
Makefile kasan, arm64: adjust shadow size for tag-based mode 2018-12-28 12:11:43 -08:00