[PATCH v4 05/36] arm64/sysreg: Add definitions for architected GCS caps

Mark Brown
2023-08-07T22:02:10Z

The architecture defines a format for guarded control stack caps, used
to mark the top of an unused GCS in order to limit the potential for
exploitation via stack switching. Add definitions associated with these.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
arch/arm64/include/asm/sysreg.h | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index b481935e9314..3d7f9b25b8fb 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -730,6 +730,26 @@

#define PIRx_ELx_PERM(idx, perm) ((perm) << ((idx) * 4))

+/*
+ * Definitions for Guarded Control Stack
+ */
+
+#define GCS_CAP_ADDR_MASK GENMASK(63, 12)
+#define GCS_CAP_ADDR_SHIFT 12
+#define GCS_CAP_ADDR_WIDTH 52
+#define GCS_CAP_ADDR(x) FIELD_GET(GCS_CAP_ADDR_MASK, x)
+
+#define GCS_CAP_TOKEN_MASK GENMASK(11, 0)
+#define GCS_CAP_TOKEN_SHIFT 0
+#define GCS_CAP_TOKEN_WIDTH 12
+#define GCS_CAP_TOKEN(x) FIELD_GET(GCS_CAP_TOKEN_MASK, x)
+
+#define GCS_CAP_VALID_TOKEN 0x1
+#define GCS_CAP_IN_PROGRESS_TOKEN 0x5
+
+#define GCS_CAP(x) ((((unsigned long)x) & GCS_CAP_ADDR_MASK) | \
+ GCS_CAP_VALID_TOKEN)
+
#define ARM64_FEATURE_FIELD_BITS 4

/* Defined for compatibility only, do not add new users. */

--
2.30.2