arm64: kaslr: Put kernel vectors address in separate data page
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>
diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index 8119b49b..ec1e6d6 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -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 */
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 3eabcb1..031392e 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -1030,7 +1030,13 @@
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 @@
.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 */
/*
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 6b4260f..ddfd3c0 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -251,7 +251,10 @@
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.
*/
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index fe68a48..916d9ce 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -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);
