KVM: arm64: Add symbol at the beginning of each hyp section

Generating hyp relocations will require referencing positions at a given
offset from the beginning of hyp sections. Since the final layout will
not be determined until the linking of `vmlinux`, modify the hyp linker
script to insert a symbol at the first byte of each hyp section to use
as an anchor. The linker of `vmlinux` will place the symbols together
with the sections.

Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210105180541.65031-4-dbrazdil@google.com

diff --git a/arch/arm64/include/asm/hyp_image.h b/arch/arm64/include/asm/hyp_image.h
index daa1a1d..737ded6 100644 (file)
--- a/arch/arm64/include/asm/hyp_image.h
+++ b/arch/arm64/include/asm/hyp_image.h
@@ -7,6 +7,9 @@
 #ifndef __ARM64_HYP_IMAGE_H__
 #define __ARM64_HYP_IMAGE_H__
 
+#define __HYP_CONCAT(a, b)     a ## b
+#define HYP_CONCAT(a, b)       __HYP_CONCAT(a, b)
+
 /*
  * KVM nVHE code has its own symbol namespace prefixed with __kvm_nvhe_,
  * to separate it from the kernel proper.
@@ -21,9 +24,31 @@
  */
 #define HYP_SECTION_NAME(NAME) .hyp##NAME
 
+/* Symbol defined at the beginning of each hyp section. */
+#define HYP_SECTION_SYMBOL_NAME(NAME) \
+       HYP_CONCAT(__hyp_section_, HYP_SECTION_NAME(NAME))
+
+/*
+ * Helper to generate linker script statements starting a hyp section.
+ *
+ * A symbol with a well-known name is defined at the first byte. This
+ * is used as a base for hyp relocations (see gen-hyprel.c). It must
+ * be defined inside the section so the linker of `vmlinux` cannot
+ * separate it from the section data.
+ */
+#define BEGIN_HYP_SECTION(NAME)                                \
+       HYP_SECTION_NAME(NAME) : {                      \
+               HYP_SECTION_SYMBOL_NAME(NAME) = .;
+
+/* Helper to generate linker script statements ending a hyp section. */
+#define END_HYP_SECTION                                        \
+       }
+
 /* Defines an ELF hyp section from input section @NAME and its subsections. */
-#define HYP_SECTION(NAME) \
-       HYP_SECTION_NAME(NAME) : { *(NAME NAME##.*) }
+#define HYP_SECTION(NAME)                      \
+       BEGIN_HYP_SECTION(NAME)                 \
+               *(NAME NAME##.*)                \
+       END_HYP_SECTION
 
 /*
  * Defines a linker script alias of a kernel-proper symbol referenced by

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
index cfdc59b..cd119d8 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
@@ -22,7 +22,7 @@ SECTIONS {
         * alignment for when linking into vmlinux.
         */
        . = ALIGN(PAGE_SIZE);
-       HYP_SECTION_NAME(.data..percpu) : {
+       BEGIN_HYP_SECTION(.data..percpu)
                PERCPU_INPUT(L1_CACHE_BYTES)
-       }
+       END_HYP_SECTION
 }