[PATCH v5 04/12] x86/hyperlaunch: Add helpers to locate multiboot modules

[Alejandro Vallejo <agarciav@xxxxxxx>]

Hyperlaunch mandates either a reg or module-index DT prop on nodes that
contain `multiboot,module" under their "compatible" prop. This patch
introduces a helper to generically find such index, appending the module
to the list of modules if it wasn't already (i.e: because it's given via
the "reg" prop).

Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Signed-off-by: Alejandro Vallejo <agarciav@xxxxxxx>
---
v5:
  * s/read_fdt_prop_as_reg/fdt_prop_as_reg/
  * Move the _u32() prop helper to fdt.c
---
 xen/common/domain-builder/fdt.c  | 172 +++++++++++++++++++++++++++++++
 xen/common/domain-builder/fdt.h  |   1 +
 xen/include/xen/domain-builder.h |   4 +
 3 files changed, 177 insertions(+)

diff --git a/xen/common/domain-builder/fdt.c b/xen/common/domain-builder/fdt.c
index c1ccba39a2..11f0436e85 100644
--- a/xen/common/domain-builder/fdt.c
+++ b/xen/common/domain-builder/fdt.c
@@ -13,6 +13,178 @@
 
 #include "fdt.h"
 
+static int __init fdt_prop_as_u32(const struct fdt_property *prop,
+                                  uint32_t *val)
+{
+    if ( !prop || fdt32_to_cpu(prop->len) < sizeof(u32) )
+        return -EINVAL;
+
+    *val = fdt32_to_cpu(*(const fdt32_t *)prop->data);
+    return 0;
+}
+
+/*
+ * Unpacks a "reg" property into its address and size constituents.
+ *
+ * @param prop          Pointer to an FDT "reg" property.
+ * @param address_cells Number of 4-octet cells that make up an "address".
+ * @param size_cells    Number of 4-octet cells that make up a "size".
+ * @param p_addr[out]   Address encoded in the property.
+ * @param p_size[out]   Size encoded in the property.
+ * @returns             -EINVAL on malformed property, 0 otherwise.
+ */
+static int __init fdt_prop_as_reg(const struct fdt_property *prop,
+                                  int address_cells, int size_cells,
+                                  uint64_t *p_addr, uint64_t *p_size)
+{
+    const fdt32_t *cell = (const fdt32_t *)prop->data;
+    uint64_t addr, size;
+
+    if ( fdt32_to_cpu(prop->len) !=
+         (address_cells + size_cells) * sizeof(*cell) )
+    {
+        printk(XENLOG_ERR "  cannot read reg %lu+%lu from prop len %u\n",
+            address_cells * sizeof(*cell), size_cells * sizeof(*cell),
+            fdt32_to_cpu(prop->len));
+        return -EINVAL;
+    }
+
+    switch ( address_cells )
+    {
+    case 1:
+        addr = fdt32_to_cpu(*cell);
+        break;
+    case 2:
+        addr = fdt64_to_cpu(*(const fdt64_t *)cell);
+        break;
+    default:
+        printk(XENLOG_ERR "  unsupported address_cells=%d\n", address_cells);
+        return -EINVAL;
+    }
+
+    cell += address_cells;
+    switch ( size_cells )
+    {
+    case 1:
+        size = fdt32_to_cpu(*cell);
+        break;
+    case 2:
+        size = fdt64_to_cpu(*(const fdt64_t *)cell);
+        break;
+    default:
+        printk(XENLOG_ERR "  unsupported size_cells=%d\n", size_cells);
+        return -EINVAL;
+    }
+
+    *p_addr = addr;
+    *p_size = size;
+
+    return 0;
+}
+
+/*
+ * Locate a multiboot module given its node offset in the FDT.
+ *
+ * The module location may be given via either FDT property:
+ *     * reg = <address, size>
+ *         * Mutates `bi` to append the module.
+ *     * module-index = <idx>
+ *         * Leaves `bi` unchanged.
+ *
+ * @param fdt           Pointer to the full FDT.
+ * @param node          Offset for the module node.
+ * @param address_cells Number of 4-octet cells that make up an "address".
+ * @param size_cells    Number of 4-octet cells that make up a "size".
+ * @param bi[inout]     Xen's representation of the boot parameters.
+ * @return              -EINVAL on malformed nodes, otherwise
+ *                      index inside `bi->mods`
+ */
+int __init fdt_read_multiboot_module(const void *fdt, int node,
+                                     int address_cells, int size_cells,
+                                     struct boot_info *bi)
+{
+    const struct fdt_property *prop;
+    uint64_t addr, size;
+    int ret;
+    uint32_t idx;
+
+    if ( fdt_node_check_compatible(fdt, node, "multiboot,module") )
+    {
+        printk(XENLOG_ERR "  bad module. multiboot,module not found");
+        return -ENODATA;
+    }
+
+    /* Location given as a `module-index` property. */
+    if ( (prop = fdt_get_property(fdt, node, "module-index", NULL)) )
+    {
+        if ( fdt_get_property(fdt, node, "reg", NULL) )
+        {
+            printk(XENLOG_ERR "  found both reg and module-index for 
module\n");
+            return -EINVAL;
+        }
+        if ( (ret = fdt_prop_as_u32(prop, &idx)) )
+        {
+            printk(XENLOG_ERR "  bad module-index prop\n");
+            return ret;
+        }
+        if ( idx >= MAX_NR_BOOTMODS )
+        {
+            printk(XENLOG_ERR "  module-index overflow. %s=%u\n",
+                   STR(MAX_NR_BOOTMODS), MAX_NR_BOOTMODS);
+            return -EINVAL;
+        }
+
+        return idx;
+    }
+
+    /* Otherwise location given as a `reg` property. */
+    if ( !(prop = fdt_get_property(fdt, node, "reg", NULL)) )
+    {
+        printk(XENLOG_ERR "  no location for multiboot,module\n");
+        return -EINVAL;
+    }
+    if ( fdt_get_property(fdt, node, "module-index", NULL) )
+    {
+        printk(XENLOG_ERR "  found both reg and module-index for module\n");
+        return -EINVAL;
+    }
+
+    ret = fdt_prop_as_reg(prop, address_cells, size_cells, &addr, &size);
+    if ( ret < 0 )
+    {
+        printk(XENLOG_ERR "  failed reading reg for multiboot,module\n");
+        return -EINVAL;
+    }
+
+    idx = bi->nr_modules;
+    if ( idx > MAX_NR_BOOTMODS )
+    {
+        /*
+         * MAX_NR_BOOTMODS must fit in 31 bits so it's representable in the
+         * positive side of an int; for the return value.
+         */
+        BUILD_BUG_ON(MAX_NR_BOOTMODS > (uint64_t)INT_MAX);
+        printk(XENLOG_ERR "  idx=%u exceeds len=%u\n", idx, MAX_NR_BOOTMODS);
+        return -EINVAL;
+    }
+
+    /*
+     * Append new module to the existing list
+     *
+     * Note that bi->nr_modules points to Xen itself, so we must shift it first
+     */
+    bi->nr_modules++;
+    bi->mods[bi->nr_modules] = bi->mods[idx];
+    bi->mods[idx] = (struct boot_module){
+        .start = addr,
+        .size = size,
+    };
+
+    printk(XENLOG_INFO "  module[%u]: addr %lx size %lx\n", idx, addr, size);
+
+    return idx;
+}
+
 static int __init find_hyperlaunch_node(const void *fdt)
 {
     int hv_node = fdt_path_offset(fdt, "/chosen/hypervisor");
diff --git a/xen/common/domain-builder/fdt.h b/xen/common/domain-builder/fdt.h
index 826c0f01e5..f48456acd2 100644
--- a/xen/common/domain-builder/fdt.h
+++ b/xen/common/domain-builder/fdt.h
@@ -3,6 +3,7 @@
 #define __XEN_DOMAIN_BUILDER_FDT_H__
 
 #include <xen/domain-builder.h>
+#include <xen/libfdt/libfdt-xen.h>
 
 struct boot_info;
 
diff --git a/xen/include/xen/domain-builder.h b/xen/include/xen/domain-builder.h
index cbb3cbea7c..3ac3a0ab84 100644
--- a/xen/include/xen/domain-builder.h
+++ b/xen/include/xen/domain-builder.h
@@ -28,4 +28,8 @@ static inline enum fdt_kind builder_init(struct boot_info *bi)
 }
 #endif /* !IS_ENABLED(CONFIG_DOMAIN_BUILDER) */
 
+int fdt_read_multiboot_module(const void *fdt, int node,
+                              int address_cells, int size_cells,
+                              struct boot_info *bi)
+
 #endif /* __XEN_DOMAIN_BUILDER_H__ */
-- 
2.43.0