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arm64: alternative: Add support for patching adrp instructions 

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 <will.deacon@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Andre Przywara <andre.przywara@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Suzuki K Poulose 2016-09-09 14:07:13 +01:00 committed by Will Deacon
parent 46084bc253
commit c831b2ae25
1 changed files with 15 additions and 0 deletions
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15
arch/arm64/kernel/alternative.c
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@ -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