FROMLIST: 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>
(cherry picked from git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git
 commit 6c27c4082f4f70b9f41df4d0adf51128b40351df)

Change-Id: Iffe72dc5e7ee171d83a7b916a16146e35ddf904e
[ghackmann@google.com:
 - adjust context
 - replace ARM64_WORKAROUND_QCOM_FALKOR_E1003 alternative with
   compile-time CONFIG_ARCH_MSM8996 check]
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index 8fa98f26129af1e342244604494336a2c62698df..03a1e908b8e99105e32629a85373d9a0385061b4 100644 (file)
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -51,6 +51,7 @@ enum fixed_addresses {
        FIX_EARLYCON_MEM_BASE,
        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 1c7f6f9961a15fce382ddaf879731361f2897aa2..5b13ed6ec742a2e77d8acc9b77adfa3b36038fc6 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -992,7 +992,15 @@ __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
+#ifndef CONFIG_ARCH_MSM8996
+       isb
+#endif
+       ldr     x30, [x30]
+#else
        ldr     x30, =vectors
+#endif
        prfm    plil1strm, [x30, #(1b - tramp_vectors)]
        msr     vbar_el1, x30
        add     x30, x30, #(1b - tramp_vectors)
@@ -1035,6 +1043,14 @@ 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 a0432ab720cd577582c482c7dcface1d6f225d81..6e4832def25440e08f77857bfbe701bb330b5b15 100644 (file)
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -224,6 +224,10 @@ ASSERT(__hyp_idmap_text_end - (__hyp_idmap_text_start & ~(SZ_4K - 1)) <= SZ_4K,
 ASSERT(__idmap_text_end - (__idmap_text_start & ~(SZ_4K - 1)) <= SZ_4K,
        "ID map text too big or misaligned")
 
+#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 a383ec16f1b738dc45ac9acd2af40f43f03b93b4..0029b0b954381b0dd184f6fc95a063e5f1b40ee4 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -510,8 +510,16 @@ static int __init map_entry_trampoline(void)
        __create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS, PAGE_SIZE,
                             prot, late_pgtable_alloc);
 
-       /* ...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);