[PATCH v2 3/8] KVM: arm64: Add symbol at the beginning of each hyp section

David Brazdil
2021-01-05T18:06:49Z

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>
---
arch/arm64/include/asm/hyp_image.h | 29 +++++++++++++++++++++++++++--
arch/arm64/kvm/hyp/nvhe/hyp.lds.S | 4 ++--
2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/hyp_image.h b/arch/arm64/include/asm/hyp_image.h
index daa1a1da539e..f97b774b58f4 100644
--- 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) __HYP_CONCAT(a, b)
+#define __HYP_CONCAT(a, b) 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 cfdc59b4329b..cd119d82d8e3 100644
--- 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
}
--
2.29.2.729.g45daf8777d-goog