arm64: entry: Move the trampoline data page before the text page

commit c091fb6ae059cda563b2a4d93fdbc548ef34e1d6 upstream.

The trampoline code has a data page that holds the address of the vectors,
which is unmapped when running in user-space. This ensures that with
CONFIG_RANDOMIZE_BASE, the randomised address of the kernel can't be
discovered until after the kernel has been mapped.

If the trampoline text page is extended to include multiple sets of
vectors, it will be larger than a single page, making it tricky to
find the data page without knowing the size of the trampoline text
pages, which will vary with PAGE_SIZE.

Move the data page to appear before the text page. This allows the
data page to be found without knowing the size of the trampoline text
pages. 'tramp_vectors' is used to refer to the beginning of the
.entry.tramp.text section, do that explicitly.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
[ removed SDEI for backport ]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index ec1e6d6fa14ccd4c14a735a8732a7a468c709276..c0cfc6d3bf9f8336f6db9cdd9b7b2576e32ee1ef 100644 (file)
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -59,8 +59,8 @@ enum fixed_addresses {
 #endif /* CONFIG_ACPI_APEI_GHES */
 
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
-       FIX_ENTRY_TRAMP_DATA,
        FIX_ENTRY_TRAMP_TEXT,
+       FIX_ENTRY_TRAMP_DATA,
 #define TRAMP_VALIAS           (__fix_to_virt(FIX_ENTRY_TRAMP_TEXT))
 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
        __end_of_permanent_fixed_addresses,

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index b3014ed0ea8afe24824437e1f26d6ba832a082f5..0669d05bd63cc64cfb16591248520a078f193249 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -1019,6 +1019,11 @@ alternative_else_nop_endif
         */
        .endm
 
+       .macro tramp_data_page  dst
+       adr     \dst, .entry.tramp.text
+       sub     \dst, \dst, PAGE_SIZE
+       .endm
+
        .macro tramp_ventry, regsize = 64
        .align  7
 1:
@@ -1035,7 +1040,7 @@ alternative_else_nop_endif
 2:
        tramp_map_kernel        x30
 #ifdef CONFIG_RANDOMIZE_BASE
-       adr     x30, tramp_vectors + PAGE_SIZE
+       tramp_data_page         x30
 alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003
        ldr     x30, [x30]
 #else