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

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commit b28a8eebe81c186fdb1a0078263b30576c8e1f42 upstream.

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: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
James Morse 2022-03-15 18:24:09 +00:00 committed by Greg Kroah-Hartman
parent 3abf6e8a7a
commit 1bb1944970
1 changed files with 16 additions and 19 deletions
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35
arch/arm64/kernel/entry.S
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@ -1063,6 +1063,15 @@ 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
@ -1093,13 +1102,8 @@ 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
@ -1183,7 +1187,12 @@ END(tramp_exit_compat)
.align PAGE_SHIFT
.globl __entry_tramp_data_start
__entry_tramp_data_start:
__entry_tramp_data_vectors:
.quad vectors
#ifdef CONFIG_ARM_SDE_INTERFACE
__entry_tramp_data___sdei_asm_trampoline_next_handler:
.quad __sdei_asm_handler
#endif /* CONFIG_ARM_SDE_INTERFACE */
.popsection // .rodata
#endif /* CONFIG_RANDOMIZE_BASE */
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
@ -1310,13 +1319,7 @@ ENTRY(__sdei_asm_entry_trampoline)
*/
1: str x4, [x1, #(SDEI_EVENT_INTREGS + S_ORIG_ADDR_LIMIT)]
#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_trampoline_next_handler
br x4
ENDPROC(__sdei_asm_entry_trampoline)
NOKPROBE(__sdei_asm_entry_trampoline)
@ -1339,12 +1342,6 @@ ENDPROC(__sdei_asm_exit_trampoline)
NOKPROBE(__sdei_asm_exit_trampoline)
.ltorg
.popsection // .entry.tramp.text
#ifdef CONFIG_RANDOMIZE_BASE
.pushsection ".rodata", "a"
__sdei_asm_trampoline_next_handler:
.quad __sdei_asm_handler
.popsection // .rodata
#endif /* CONFIG_RANDOMIZE_BASE */
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
/*