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arm64: kaslr: Put kernel vectors address in separate data page

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The literal pool entry for identifying the vectors base is the only piece
of information in the trampoline page that identifies the true location
of the kernel.

This patch moves it into a page-aligned region of the .rodata section
and maps this adjacent to the trampoline text via an additional fixmap
entry, which protects against any accidental leakage of the trampoline
contents.

Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon 2017-12-06 11:24:02 +00:00
parent b519538dfe
commit 6c27c4082f
4 changed files with 28 additions and 2 deletions
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1
arch/arm64/include/asm/fixmap.h
View File

@ -59,6 +59,7 @@ enum fixed_addresses {
#endif /* CONFIG_ACPI_APEI_GHES */
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
FIX_ENTRY_TRAMP_DATA,
FIX_ENTRY_TRAMP_TEXT,
#define TRAMP_VALIAS (__fix_to_virt(FIX_ENTRY_TRAMP_TEXT))
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */

14
arch/arm64/kernel/entry.S
View File

@ -1030,7 +1030,13 @@ alternative_else_nop_endif
msr tpidrro_el0, x30 // Restored in kernel_ventry
.endif
tramp_map_kernel x30
#ifdef CONFIG_RANDOMIZE_BASE
adr x30, tramp_vectors + PAGE_SIZE
alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003
ldr x30, [x30]
#else
ldr x30, =vectors
#endif
prfm plil1strm, [x30, #(1b - tramp_vectors)]
msr vbar_el1, x30
add x30, x30, #(1b - tramp_vectors)
@ -1073,6 +1079,14 @@ END(tramp_exit_compat)
.ltorg
.popsection // .entry.tramp.text
#ifdef CONFIG_RANDOMIZE_BASE
.pushsection ".rodata", "a"
.align PAGE_SHIFT
.globl __entry_tramp_data_start
__entry_tramp_data_start:
.quad vectors
.popsection // .rodata
#endif /* CONFIG_RANDOMIZE_BASE */
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
/*

5
arch/arm64/kernel/vmlinux.lds.S
View File

@ -251,7 +251,10 @@ ASSERT(__idmap_text_end - (__idmap_text_start & ~(SZ_4K - 1)) <= SZ_4K,
ASSERT(__hibernate_exit_text_end - (__hibernate_exit_text_start & ~(SZ_4K - 1))
<= SZ_4K, "Hibernate exit text too big or misaligned")
#endif
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
ASSERT((__entry_tramp_text_end - __entry_tramp_text_start) == PAGE_SIZE,
"Entry trampoline text too big")
#endif
/*
* If padding is applied before .head.text, virt<->phys conversions will fail.
*/

10
arch/arm64/mm/mmu.c
View File

@ -541,8 +541,16 @@ static int __init map_entry_trampoline(void)
__create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS, PAGE_SIZE,
prot, pgd_pgtable_alloc, 0);
/* ...as well as the kernel page table */
/* Map both the text and data into the kernel page table */
__set_fixmap(FIX_ENTRY_TRAMP_TEXT, pa_start, prot);
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
extern char __entry_tramp_data_start[];
__set_fixmap(FIX_ENTRY_TRAMP_DATA,
__pa_symbol(__entry_tramp_data_start),
PAGE_KERNEL_RO);
}
return 0;
}
core_initcall(map_entry_trampoline);