[PATCH v4 6/9] arm64: alternative: Add support for patching adrp instructions
From: suzuki.poulose@arm.com (Suzuki K Poulose)
Date: 2016-09-09 13:08:45
Also in:
lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
adrp uses PC-relative address offset to a page (of 4K size) of a symbol. If it appears in an alternative code patched in, we should adjust the offset to reflect the address where it will be run from. This patch adds support for fixing the offset for adrp instructions. Cc: Will Deacon <redacted> Cc: Marc Zyngier <redacted> Cc: Andre Przywara <andre.przywara@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> --- arch/arm64/kernel/alternative.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index 992918d..06d650f 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c@@ -58,6 +58,8 @@ static bool branch_insn_requires_update(struct alt_instr *alt, unsigned long pc) BUG(); } +#define align_down(x, a) ((unsigned long)(x) & ~(((unsigned long)(a)) - 1)) + static u32 get_alt_insn(struct alt_instr *alt, u32 *insnptr, u32 *altinsnptr) { u32 insn;
@@ -79,6 +81,19 @@ static u32 get_alt_insn(struct alt_instr *alt, u32 *insnptr, u32 *altinsnptr) offset = target - (unsigned long)insnptr; insn = aarch64_set_branch_offset(insn, offset); } + } else if (aarch64_insn_is_adrp(insn)) { + s32 orig_offset, new_offset; + unsigned long target; + + /* + * If we're replacing an adrp instruction, which uses PC-relative + * immediate addressing, adjust the offset to reflect the new + * PC. adrp operates on 4K aligned addresses. + */ + orig_offset = aarch64_insn_adrp_get_offset(insn); + target = align_down(altinsnptr, SZ_4K) + orig_offset; + new_offset = target - align_down(insnptr, SZ_4K); + insn = aarch64_insn_adrp_set_offset(insn, new_offset); } else if (aarch64_insn_uses_literal(insn)) { /* * Disallow patching unhandled instructions using PC relative
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2.7.4