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authorJames Morse <james.morse@arm.com>2021-11-23 15:43:31 +0000
committerJames Morse <james.morse@arm.com>2022-02-15 17:39:14 +0000
commitc091fb6ae059cda563b2a4d93fdbc548ef34e1d6 (patch)
treee3d6f3a0ed2f921d6365ef879a5c59158344d7be
parent03aff3a77a58b5b52a77e00537a42090ad57b80b (diff)
downloadlinux-c091fb6ae059cda563b2a4d93fdbc548ef34e1d6.tar.bz2
arm64: entry: Move the trampoline data page before the text page
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>
-rw-r--r--arch/arm64/include/asm/fixmap.h2
-rw-r--r--arch/arm64/kernel/entry.S9
2 files changed, 8 insertions, 3 deletions
diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
index 4335800201c9..0aabc0253b18 100644
--- a/arch/arm64/include/asm/fixmap.h
+++ b/arch/arm64/include/asm/fixmap.h
@@ -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,
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 45e89135dc11..d8a76869e873 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -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