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

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>
[ Removed SDEI for stable backport ]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 6e637315fd806ce641620f9aa2b0249eb3be802d..ec46c89759a8a5e566ca9117d21f2392ec93d561 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -921,6 +921,15 @@ __ni_sys_trace:
        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
@@ -951,13 +960,7 @@ __ni_sys_trace:
        b       .
 2:
        tramp_map_kernel        x30
-#ifdef CONFIG_RANDOMIZE_BASE
-       tramp_data_page         x30
-       isb
-       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
@@ -1037,7 +1040,12 @@ 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 */