arm64: vmlinux.ld: Add mmuoff data sections and move mmuoff text into idmap

Resume from hibernate needs to clean any text executed by the kernel with
the MMU off to the PoC. Collect these functions together into the
.idmap.text section as all this code is tightly coupled and also needs
the same cleaning after resume.

Data is more complicated, secondary_holding_pen_release is written with
the MMU on, clean and invalidated, then read with the MMU off. In contrast
__boot_cpu_mode is written with the MMU off, the corresponding cache line
is invalidated, so when we read it with the MMU on we don't get stale data.
These cache maintenance operations conflict with each other if the values
are within a Cache Writeback Granule (CWG) of each other.
Collect the data into two sections .mmuoff.data.read and .mmuoff.data.write,
the linker script ensures mmuoff.data.write section is aligned to the
architectural maximum CWG of 2KB.

Signed-off-by: James Morse <james.morse@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 659963d40bb4..5ce9b2929e0d 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -185,6 +185,25 @@ SECTIONS
 	_data = .;
 	_sdata = .;
 	RW_DATA_SECTION(L1_CACHE_BYTES, PAGE_SIZE, THREAD_SIZE)
+
+	/*
+	 * Data written with the MMU off but read with the MMU on requires
+	 * cache lines to be invalidated, discarding up to a Cache Writeback
+	 * Granule (CWG) of data from the cache. Keep the section that
+	 * requires this type of maintenance to be in its own Cache Writeback
+	 * Granule (CWG) area so the cache maintenance operations don't
+	 * interfere with adjacent data.
+	 */
+	.mmuoff.data.write : ALIGN(SZ_2K) {
+		__mmuoff_data_start = .;
+		*(.mmuoff.data.write)
+	}
+	. = ALIGN(SZ_2K);
+	.mmuoff.data.read : {
+		*(.mmuoff.data.read)
+		__mmuoff_data_end = .;
+	}
+
 	PECOFF_EDATA_PADDING
 	_edata = .;