[PATCH 4.19 37/57] arm64: entry: Add macro for reading symbol addresses from the trampoline

Greg Kroah-Hartman
2022-03-21T14:05:43Z

From: James Morse <james.morse@arm.com>

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm64/kernel/entry.S | 35 ++++++++++++++++-------------------
1 file changed, 16 insertions(+), 19 deletions(-)

--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -970,6 +970,15 @@ 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
@@ -1000,13 +1009,8 @@ 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
prfm plil1strm, [x30, #(1b - \vector_start)]
msr vbar_el1, x30
isb
@@ -1086,7 +1090,12 @@ 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_handler:
+ .quad __sdei_asm_handler
+#endif /* CONFIG_ARM_SDE_INTERFACE */
.popsection // .rodata
#endif /* CONFIG_RANDOMIZE_BASE */
#endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
@@ -1213,13 +1222,7 @@ 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_handler
br x4
ENDPROC(__sdei_asm_entry_trampoline)
NOKPROBE(__sdei_asm_entry_trampoline)
@@ -1242,12 +1245,6 @@ 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 */

/*