Currently, the hyp code cannot make full use of a bss, as the kernel
section is mapped read-only.
While this mapping could simply be changed to read-write, it would
intermingle even more the hyp and kernel state than they currently are.
Instead, introduce a __hyp_bss section, that uses reserved pages, and
create the appropriate RW hyp mappings during KVM init.
Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx>
---
arch/arm64/include/asm/sections.h | 1 +
arch/arm64/kernel/vmlinux.lds.S | 7 +++++++
arch/arm64/kvm/arm.c | 11 +++++++++++
arch/arm64/kvm/hyp/nvhe/hyp.lds.S | 1 +
4 files changed, 20 insertions(+)
diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h
index 8ff579361731..f58cf493de16 100644
--- a/arch/arm64/include/asm/sections.h
+++ b/arch/arm64/include/asm/sections.h
@@ -12,6 +12,7 @@ extern char __hibernate_exit_text_start[], __hibernate_exit_text_end[];
extern char __hyp_idmap_text_start[], __hyp_idmap_text_end[];
extern char __hyp_text_start[], __hyp_text_end[];
extern char __hyp_data_ro_after_init_start[], __hyp_data_ro_after_init_end[];
+extern char __hyp_bss_start[], __hyp_bss_end[];
extern char __idmap_text_start[], __idmap_text_end[];
extern char __initdata_begin[], __initdata_end[];
extern char __inittext_begin[], __inittext_end[];
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 4382b5d0645d..ded78a25365d 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -8,6 +8,13 @@
#define RO_EXCEPTION_TABLE_ALIGN 8
#define RUNTIME_DISCARD_EXIT
+#define BSS_FIRST_SECTIONS \
+ . = ALIGN(PAGE_SIZE); \
+ __hyp_bss_start = .; \
+ *(.hyp.bss) \
+ . = ALIGN(PAGE_SIZE); \
+ __hyp_bss_end = .;
+
#include <asm-generic/vmlinux.lds.h>
#include <asm/cache.h>
#include <asm/hyp_image.h>
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 7335eb4fb0bd..882eb383bd75 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1709,7 +1709,18 @@ static int init_hyp_mode(void)
goto out_err;
}
+ /*
+ * .hyp.bss is placed at the beginning of the .bss section, so map that
+ * part RW, and the rest RO as the hyp shouldn't be touching it.
+ */
err = create_hyp_mappings(kvm_ksym_ref(__bss_start),
+ kvm_ksym_ref(__hyp_bss_end), PAGE_HYP);
+ if (err) {
+ kvm_err("Cannot map hyp bss section: %d\n", err);
+ goto out_err;
+ }
+
+ err = create_hyp_mappings(kvm_ksym_ref(__hyp_bss_end),
kvm_ksym_ref(__bss_stop), PAGE_HYP_RO);
if (err) {
kvm_err("Cannot map bss section\n");
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
index 5d76ff2ba63e..dc281d90063e 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
@@ -17,4 +17,5 @@ SECTIONS {
PERCPU_INPUT(L1_CACHE_BYTES)
}
HYP_SECTION(.data..ro_after_init)
+ HYP_SECTION(.bss)
}
--
2.29.2.299.gdc1121823c-goog
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