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

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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>
Signed-off-by: James Morse <james.morse@arm.com>
This commit is contained in:
James Morse 2021-11-23 15:43:31 +00:00
parent 03aff3a77a
commit c091fb6ae0
2 changed files with 8 additions and 3 deletions
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2
arch/arm64/include/asm/fixmap.h
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@ -62,8 +62,8 @@ 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,

9
arch/arm64/kernel/entry.S
View File

@ -644,6 +644,11 @@ 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:
@ -660,7 +665,7 @@ 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
@ -851,7 +856,7 @@ SYM_CODE_START(__sdei_asm_entry_trampoline)
1: str x4, [x1, #(SDEI_EVENT_INTREGS + S_SDEI_TTBR1)]
#ifdef CONFIG_RANDOMIZE_BASE
adr x4, tramp_vectors + PAGE_SIZE
tramp_data_page x4
add x4, x4, #:lo12:__sdei_asm_trampoline_next_handler
ldr x4, [x4]
#else