From: Will Deacon <will.deacon@xxxxxxx>
commit 6c27c4082f4f upstream.
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@xxxxxxxxxx>
Tested-by: Laura Abbott <labbott@xxxxxxxxxx>
Tested-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
[Alex: avoid ARM64_WORKAROUND_QCOM_FALKOR_E1003 dependency]
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxx> [v4.9 backport]
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> [v4.9 backport]
---
arch/arm64/include/asm/fixmap.h | 1 +
arch/arm64/kernel/entry.S | 14 ++++++++++++++
arch/arm64/kernel/vmlinux.lds.S | 5 ++++-
arch/arm64/mm/mmu.c | 10 +++++++++-
4 files changed, 28 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index 7b1d88c18143..d8e58051f32d 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -53,6 +53,7 @@ enum fixed_addresses {
FIX_TEXT_POKE0,
#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 b16d0534cda3..805dc76517c3 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -881,7 +881,13 @@ __ni_sys_trace:
msr tpidrro_el0, x30 // Restored in kernel_ventry
.endif
tramp_map_kernel x30
+#ifdef CONFIG_RANDOMIZE_BASE
+ adr x30, tramp_vectors + PAGE_SIZE
+ isb
+ ldr x30, [x30]
+#else
ldr x30, =vectors
+#endif
prfm plil1strm, [x30, #(1b - tramp_vectors)]
msr vbar_el1, x30
add x30, x30, #(1b - tramp_vectors)
@@ -924,6 +930,14 @@ 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 */
/*
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 466a43adec9f..6a584558b29d 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -252,7 +252,10 @@ 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.
*/
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 3a57fec16b32..4cd4862845cd 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -435,8 +435,16 @@ 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);
--
2.11.0