arm64/module: switch to ADRP/ADD sequences for PLT entries

Now that we have switched to the small code model entirely, and
reduced the extended KASLR range to 4 GB, we can be sure that the
targets of relative branches that are out of range are in range
for a ADRP/ADD pair, which is one instruction shorter than our
current MOVN/MOVK/MOVK sequence, and is more idiomatic and so it
is more likely to be implemented efficiently by micro-architectures.

So switch over the ordinary PLT code and the special handling of
the Cortex-A53 ADRP errata, as well as the ftrace trampline
handling.

Reviewed-by: Torsten Duwe <duwe@lst.de>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
[will: Added a couple of comments in the plt equality check]
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
index c2abe59c6f8f..f713e2fc4d75 100644
--- a/arch/arm64/kernel/module.c
+++ b/arch/arm64/kernel/module.c
@@ -203,9 +203,7 @@ static int reloc_insn_adrp(struct module *mod, Elf64_Shdr *sechdrs,
 {
 	u32 insn;
 
-	if (!IS_ENABLED(CONFIG_ARM64_ERRATUM_843419) ||
-	    !cpus_have_const_cap(ARM64_WORKAROUND_843419) ||
-	    ((u64)place & 0xfff) < 0xff8)
+	if (!is_forbidden_offset_for_adrp(place))
 		return reloc_insn_imm(RELOC_OP_PAGE, place, val, 12, 21,
 				      AARCH64_INSN_IMM_ADR);