Merge branch 'for-next/kasan' into for-next/core

Optimise out-of-line KASAN checking when using software tagging.

* for-next/kasan:
  kasan: arm64: support specialized outlined tag mismatch checks

2 files changed, 78 insertions, 0 deletions

diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
index c97b10de5e87..6dd56a49790a 100644
--- a/arch/arm64/lib/Makefile
+++ b/arch/arm64/lib/Makefile
@@ -18,3 +18,5 @@ obj-$(CONFIG_CRC32) += crc32.o
 obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
 
 obj-$(CONFIG_ARM64_MTE) += mte.o
+
+obj-$(CONFIG_KASAN_SW_TAGS) += kasan_sw_tags.o
diff --git a/arch/arm64/lib/kasan_sw_tags.S b/arch/arm64/lib/kasan_sw_tags.S
new file mode 100644
index 000000000000..5b04464c045e
--- /dev/null
+++ b/arch/arm64/lib/kasan_sw_tags.S
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Google LLC
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * Report a tag mismatch detected by tag-based KASAN.
+ *
+ * A compiler-generated thunk calls this with a non-AAPCS calling
+ * convention. Upon entry to this function, registers are as follows:
+ *
+ * x0:         fault address (see below for restore)
+ * x1:         fault description (see below for restore)
+ * x2 to x15:  callee-saved
+ * x16 to x17: safe to clobber
+ * x18 to x30: callee-saved
+ * sp:         pre-decremented by 256 bytes (see below for restore)
+ *
+ * The caller has decremented the SP by 256 bytes, and created a
+ * structure on the stack as follows:
+ *
+ * sp + 0..15:    x0 and x1 to be restored
+ * sp + 16..231:  free for use
+ * sp + 232..247: x29 and x30 (same as in GPRs)
+ * sp + 248..255: free for use
+ *
+ * Note that this is not a struct pt_regs.
+ *
+ * To call a regular AAPCS function we must save x2 to x15 (which we can
+ * store in the gaps), and create a frame record (for which we can use
+ * x29 and x30 spilled by the caller as those match the GPRs).
+ *
+ * The caller expects x0 and x1 to be restored from the structure, and
+ * for the structure to be removed from the stack (i.e. the SP must be
+ * incremented by 256 prior to return).
+ */
+SYM_CODE_START(__hwasan_tag_mismatch)
+#ifdef BTI_C
+	BTI_C
+#endif
+	add	x29, sp, #232
+	stp	x2, x3, [sp, #8 * 2]
+	stp	x4, x5, [sp, #8 * 4]
+	stp	x6, x7, [sp, #8 * 6]
+	stp	x8, x9, [sp, #8 * 8]
+	stp	x10, x11, [sp, #8 * 10]
+	stp	x12, x13, [sp, #8 * 12]
+	stp	x14, x15, [sp, #8 * 14]
+#ifndef CONFIG_SHADOW_CALL_STACK
+	str	x18, [sp, #8 * 18]
+#endif
+
+	mov	x2, x30
+	bl	kasan_tag_mismatch
+
+	ldp	x0, x1, [sp]
+	ldp	x2, x3, [sp, #8 * 2]
+	ldp	x4, x5, [sp, #8 * 4]
+	ldp	x6, x7, [sp, #8 * 6]
+	ldp	x8, x9, [sp, #8 * 8]
+	ldp	x10, x11, [sp, #8 * 10]
+	ldp	x12, x13, [sp, #8 * 12]
+	ldp	x14, x15, [sp, #8 * 14]
+#ifndef CONFIG_SHADOW_CALL_STACK
+	ldr	x18, [sp, #8 * 18]
+#endif
+	ldp	x29, x30, [sp, #8 * 29]
+
+	/* remove the structure from the stack */
+	add	sp, sp, #256
+	ret
+SYM_CODE_END(__hwasan_tag_mismatch)
+EXPORT_SYMBOL(__hwasan_tag_mismatch)