From fcb1dedb2d4d2f2d77a165b1078244caf13363be Mon Sep 17 00:00:00 2001
From: Bin Meng <bmeng.cn@gmail.com>
Date: Tue, 17 Mar 2020 07:59:40 -0700
Subject: lib: utils: Add a fdt_reserved_memory_fixup() helper
Add a helper routine to insert a child node of the reserved memory
node in the device tree that describes the protected memory region
done by OpenSBI via PMP.
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
---
include/sbi_utils/fdt/fdt_helper.h | 25 +++++++
lib/utils/fdt/fdt_helper.c | 142 +++++++++++++++++++++++++++++++++++++
lib/utils/fdt/objects.mk | 7 ++
3 files changed, 174 insertions(+)
create mode 100644 include/sbi_utils/fdt/fdt_helper.h
create mode 100644 lib/utils/fdt/fdt_helper.c
create mode 100644 lib/utils/fdt/objects.mk
diff --git a/include/sbi_utils/fdt/fdt_helper.h b/include/sbi_utils/fdt/fdt_helper.h
new file mode 100644
index 0000000..a6c3073
--- /dev/null
+++ b/include/sbi_utils/fdt/fdt_helper.h
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: BSD-2-Clause
+/*
+ * fdt_helper.h - Flat Device Tree manipulation helper routines
+ * Implement helper routines on top of libfdt for OpenSBI usage
+ *
+ * Copyright (C) 2020 Bin Meng <bmeng.cn@gmail.com>
+ */
+
+#ifndef __FDT_HELPER_H__
+#define __FDT_HELPER_H__
+
+/**
+ * Fix up the reserved memory node in the device tree
+ *
+ * This routine inserts a child node of the reserved memory node in the device
+ * tree that describes the protected memory region done by OpenSBI via PMP.
+ *
+ * It is recommended that platform codes call this helper in their final_init()
+ *
+ * @param fdt: device tree blob
+ * @return zero on success and -ve on failure
+ */
+int fdt_reserved_memory_fixup(void *fdt);
+
+#endif /* __FDT_HELPER_H__ */
diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
new file mode 100644
index 0000000..d95a056
--- /dev/null
+++ b/lib/utils/fdt/fdt_helper.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: BSD-2-Clause
+/*
+ * fdt_helper.c - Flat Device Tree manipulation helper routines
+ * Implement helper routines on top of libfdt for OpenSBI usage
+ *
+ * Copyright (C) 2020 Bin Meng <bmeng.cn@gmail.com>
+ */
+
+#include <libfdt.h>
+#include <sbi/riscv_asm.h>
+#include <sbi/sbi_console.h>
+#include <sbi/sbi_platform.h>
+#include <sbi/sbi_scratch.h>
+
+/**
+ * We use PMP to protect OpenSBI firmware to safe-guard it from buggy S-mode
+ * software, see pmp_init() in lib/sbi/sbi_hart.c. The protected memory region
+ * information needs to be conveyed to S-mode software (e.g.: operating system)
+ * via some well-known method.
+ *
+ * With device tree, this can be done by inserting a child node of the reserved
+ * memory node which is used to specify one or more regions of reserved memory.
+ *
+ * For the reserved memory node bindings, see Linux kernel documentation at
+ * Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
+ *
+ * Some additional memory spaces may be protected by platform codes via PMP as
+ * well, and corresponding child nodes will be inserted.
+ */
+int fdt_reserved_memory_fixup(void *fdt)
+{
+ struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
+ const struct sbi_platform *plat = sbi_platform_ptr(scratch);
+ unsigned long prot, addr, size;
+ int na = fdt_address_cells(fdt, 0);
+ int ns = fdt_size_cells(fdt, 0);
+ fdt32_t addr_high, addr_low;
+ fdt32_t size_high, size_low;
+ fdt32_t reg[4];
+ fdt32_t *val;
+ char name[32];
+ int parent, subnode;
+ int i, j;
+ int err;
+
+ if (!sbi_platform_has_pmp(plat))
+ return 0;
+
+ /* expand the device tree to accommodate new node */
+ err = fdt_open_into(fdt, fdt, fdt_totalsize(fdt) + 256);
+ if (err < 0)
+ return err;
+
+ /* try to locate the reserved memory node */
+ parent = fdt_path_offset(fdt, "/reserved-memory");
+ if (parent < 0) {
+ /* if such node does not exist, create one */
+ parent = fdt_add_subnode(fdt, 0, "reserved-memory");
+ if (parent < 0)
+ return parent;
+
+ /*
+ * reserved-memory node has 3 required properties:
+ * - #address-cells: the same value as the root node
+ * - #size-cells: the same value as the root node
+ * - ranges: should be empty
+ */
+
+ err = fdt_setprop_empty(fdt, parent, "ranges");
+ if (err < 0)
+ return err;
+
+ err = fdt_setprop_u32(fdt, parent, "#size-cells", ns);
+ if (err < 0)
+ return err;
+
+ err = fdt_setprop_u32(fdt, parent, "#address-cells", na);
+ if (err < 0)
+ return err;
+ }
+
+ /*
+ * We assume the given device tree does not contain any memory region
+ * child node protected by PMP. Normally PMP programming happens at
+ * M-mode firmware. The memory space used by OpenSBI is protected.
+ * Some additional memory spaces may be protected by platform codes.
+ *
+ * With above assumption, we create child nodes directly.
+ */
+
+ for (i = 0, j = 0; i < PMP_COUNT; i++) {
+ pmp_get(i, &prot, &addr, &size);
+ if (!(prot & PMP_A))
+ continue;
+ if (!(prot & (PMP_R | PMP_W | PMP_X))) {
+ addr_high = (u64)addr >> 32;
+ addr_low = addr;
+ size_high = (u64)size >> 32;
+ size_low = size;
+
+ if (na > 1 && addr_high)
+ sbi_snprintf(name, sizeof(name),
+ "mmode_pmp%d@%x,%x", j,
+ addr_high, addr_low);
+ else
+ sbi_snprintf(name, sizeof(name),
+ "mmode_pmp%d@%x", j,
+ addr_low);
+
+ subnode = fdt_add_subnode(fdt, parent, name);
+ if (subnode < 0)
+ return subnode;
+
+ /*
+ * Tell operating system not to create a virtual
+ * mapping of the region as part of its standard
+ * mapping of system memory.
+ */
+ err = fdt_setprop_empty(fdt, subnode, "no-map");
+ if (err < 0)
+ return err;
+
+ /* encode the <reg> property value */
+ val = reg;
+ if (na > 1)
+ *val++ = cpu_to_fdt32(addr_high);
+ *val++ = cpu_to_fdt32(addr_low);
+ if (ns > 1)
+ *val++ = cpu_to_fdt32(size_high);
+ *val++ = cpu_to_fdt32(size_low);
+
+ err = fdt_setprop(fdt, subnode, "reg", reg,
+ (na + ns) * sizeof(fdt32_t));
+ if (err < 0)
+ return err;
+
+ j++;
+ }
+ }
+
+ return 0;
+}
diff --git a/lib/utils/fdt/objects.mk b/lib/utils/fdt/objects.mk
new file mode 100644
index 0000000..062e6bd
--- /dev/null
+++ b/lib/utils/fdt/objects.mk
@@ -0,0 +1,7 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (C) 2020 Bin Meng <bmeng.cn@gmail.com>
+#
+
+libsbiutils-objs-y += fdt/fdt_helper.o
--
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