Commit b28a8eeb authored by James Morse's avatar James Morse
Browse files

arm64: entry: Add macro for reading symbol addresses from the trampoline 



The trampoline code needs to use the address of symbols in the wider
kernel, e.g. vectors. PC-relative addressing wouldn't work as the
trampoline code doesn't run at the address the linker expected.

tramp_ventry uses a literal pool, unless CONFIG_RANDOMIZE_BASE is
set, in which case it uses the data page as a literal pool because
the data page can be unmapped when running in user-space, which is
required for CPUs vulnerable to meltdown.

Pull this logic out as a macro, instead of adding a third copy
of it.

Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
parent ba268923

arch/arm64/kernel/entry.S

+16 −21
Original line number Diff line number Diff line
@@ -646,6 +646,15 @@ alternative_else_nop_endif 
	sub	\dst, \dst, PAGE_SIZE

	.endm



	.macro tramp_data_read_var	dst, var

#ifdef CONFIG_RANDOMIZE_BASE

	tramp_data_page		\dst

	add	\dst, \dst, #:lo12:__entry_tramp_data_\var

	ldr	\dst, [\dst]

#else

	ldr	\dst, =\var

#endif

	.endm



#define BHB_MITIGATION_NONE	0

#define BHB_MITIGATION_LOOP	1
@@ -676,13 +685,8 @@ alternative_else_nop_endif 
	b	.

2:

	tramp_map_kernel	x30

#ifdef CONFIG_RANDOMIZE_BASE

	tramp_data_page		x30

alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003

	ldr	x30, [x30]

#else

	ldr	x30, =vectors

#endif

	tramp_data_read_var	x30, vectors

alternative_if_not ARM64_WORKAROUND_CAVIUM_TX2_219_PRFM

	prfm	plil1strm, [x30, #(1b - \vector_start)]

alternative_else_nop_endif
@@ -765,7 +769,12 @@ SYM_CODE_END(tramp_exit_compat) 
	.pushsection ".rodata", "a"

	.align PAGE_SHIFT

SYM_DATA_START(__entry_tramp_data_start)

__entry_tramp_data_vectors:

	.quad	vectors

#ifdef CONFIG_ARM_SDE_INTERFACE

__entry_tramp_data___sdei_asm_handler:

	.quad	__sdei_asm_handler

#endif /* CONFIG_ARM_SDE_INTERFACE */

SYM_DATA_END(__entry_tramp_data_start)

	.popsection				// .rodata

#endif /* CONFIG_RANDOMIZE_BASE */
@@ -932,14 +941,7 @@ SYM_CODE_START(__sdei_asm_entry_trampoline) 
	 * Remember whether to unmap the kernel on exit.

	 */

1:	str	x4, [x1, #(SDEI_EVENT_INTREGS + S_SDEI_TTBR1)]



#ifdef CONFIG_RANDOMIZE_BASE

	tramp_data_page		x4

	add	x4, x4, #:lo12:__sdei_asm_trampoline_next_handler

	ldr	x4, [x4]

#else

	ldr	x4, =__sdei_asm_handler

#endif

	tramp_data_read_var     x4, __sdei_asm_handler

	br	x4

SYM_CODE_END(__sdei_asm_entry_trampoline)

NOKPROBE(__sdei_asm_entry_trampoline)
@@ -962,13 +964,6 @@ SYM_CODE_END(__sdei_asm_exit_trampoline) 
NOKPROBE(__sdei_asm_exit_trampoline)

	.ltorg

.popsection		// .entry.tramp.text

#ifdef CONFIG_RANDOMIZE_BASE

.pushsection ".rodata", "a"

SYM_DATA_START(__sdei_asm_trampoline_next_handler)

	.quad	__sdei_asm_handler

SYM_DATA_END(__sdei_asm_trampoline_next_handler)

.popsection		// .rodata

#endif /* CONFIG_RANDOMIZE_BASE */

#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */



/*