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Commit 5b732b09 authored by James Morse's avatar James Morse Committed by Gerrit - the friendly Code Review server
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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 cannot 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,so do that explicitly.

Change-Id: I0034331c077fbd3e49b4934d84ec009b0797bf34
Reviewed-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: 266b1ef1
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: default avatarKishor Krishna Bhat <quic_kishkris@quicinc.com>
parent 0465045e

arch/arm64/include/asm/fixmap.h

+1 −1
Original line number Diff line number Diff line
@@ -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,

arch/arm64/kernel/entry.S

+7 −2
Original line number Diff line number Diff line
@@ -1000,6 +1000,11 @@ 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:
@@ -1016,7 +1021,7 @@ 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
@@ -1169,7 +1174,7 @@ ENTRY(__sdei_asm_entry_trampoline) 
1:	str	x4, [x1, #(SDEI_EVENT_INTREGS + S_ORIG_ADDR_LIMIT)]



#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