drivers/firmware/efi/fdtparams.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2
   3 #define pr_fmt(fmt) "efi: " fmt
   4
   5 #include <linux/module.h>
   6 #include <linux/init.h>
   7 #include <linux/efi.h>
   8 #include <linux/libfdt.h>
   9 #include <linux/of_fdt.h>
  10
  11 #include <asm/unaligned.h>
  12
  13 enum {
  14         SYSTAB,
  15         MMBASE,
  16         MMSIZE,
  17         DCSIZE,
  18         DCVERS,
  19
  20         PARAMCOUNT
  21 };
  22
  23 static __initconst const char name[][22] = {
  24         [SYSTAB] = "System Table         ",
  25         [MMBASE] = "MemMap Address       ",
  26         [MMSIZE] = "MemMap Size          ",
  27         [DCSIZE] = "MemMap Desc. Size    ",
  28         [DCVERS] = "MemMap Desc. Version ",
  29 };
  30
  31 static __initconst const struct {
  32         const char      path[17];
  33         const char      params[PARAMCOUNT][26];
  34 } dt_params[] = {
  35         {
  36 #ifdef CONFIG_XEN    //  <-------17------>
  37                 .path = "/hypervisor/uefi",
  38                 .params = {
  39                         [SYSTAB] = "xen,uefi-system-table",
  40                         [MMBASE] = "xen,uefi-mmap-start",
  41                         [MMSIZE] = "xen,uefi-mmap-size",
  42                         [DCSIZE] = "xen,uefi-mmap-desc-size",
  43                         [DCVERS] = "xen,uefi-mmap-desc-ver",
  44                 }
  45         }, {
  46 #endif
  47                 .path = "/chosen",
  48                 .params = {     //  <-----------26----------->
  49                         [SYSTAB] = "linux,uefi-system-table",
  50                         [MMBASE] = "linux,uefi-mmap-start",
  51                         [MMSIZE] = "linux,uefi-mmap-size",
  52                         [DCSIZE] = "linux,uefi-mmap-desc-size",
  53                         [DCVERS] = "linux,uefi-mmap-desc-ver",
  54                 }
  55         }
  56 };
  57
  58 static int __init efi_get_fdt_prop(const void *fdt, int node, const char *pname,
  59                                    const char *rname, void *var, int size)
  60 {
  61         const void *prop;
  62         int len;
  63         u64 val;
  64
  65         prop = fdt_getprop(fdt, node, pname, &len);
  66         if (!prop)
  67                 return 1;
  68
  69         val = (len == 4) ? (u64)be32_to_cpup(prop) : get_unaligned_be64(prop);
  70
  71         if (size == 8)
  72                 *(u64 *)var = val;
  73         else
  74                 *(u32 *)var = (val < U32_MAX) ? val : U32_MAX; // saturate
  75
  76         if (efi_enabled(EFI_DBG))
  77                 pr_info("  %s: 0x%0*llx\n", rname, size * 2, val);
  78
  79         return 0;
  80 }
  81
  82 u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
  83 {
  84         const void *fdt = initial_boot_params;
  85         unsigned long systab;
  86         int i, j, node;
  87         struct {
  88                 void    *var;
  89                 int     size;
  90         } target[] = {
  91                 [SYSTAB] = { &systab,           sizeof(systab) },
  92                 [MMBASE] = { &mm->phys_map,     sizeof(mm->phys_map) },
  93                 [MMSIZE] = { &mm->size,         sizeof(mm->size) },
  94                 [DCSIZE] = { &mm->desc_size,    sizeof(mm->desc_size) },
  95                 [DCVERS] = { &mm->desc_version, sizeof(mm->desc_version) },
  96         };
  97
  98         BUILD_BUG_ON(ARRAY_SIZE(target) != ARRAY_SIZE(name));
  99         BUILD_BUG_ON(ARRAY_SIZE(target) != ARRAY_SIZE(dt_params[0].params));
 100
 101         for (i = 0; i < ARRAY_SIZE(dt_params); i++) {
 102                 node = fdt_path_offset(fdt, dt_params[i].path);
 103                 if (node < 0)
 104                         continue;
 105
 106                 if (efi_enabled(EFI_DBG))
 107                         pr_info("Getting UEFI parameters from %s in DT:\n",
 108                                 dt_params[i].path);
 109
 110                 for (j = 0; j < ARRAY_SIZE(target); j++) {
 111                         const char *pname = dt_params[i].params[j];
 112
 113                         if (!efi_get_fdt_prop(fdt, node, pname, name[j],
 114                                               target[j].var, target[j].size))
 115                                 continue;
 116                         if (!j)
 117                                 goto notfound;
 118                         pr_err("Can't find property '%s' in DT!\n", pname);
 119                         return 0;
 120                 }
 121                 return systab;
 122         }
 123 notfound:
 124         pr_info("UEFI not found.\n");
 125         return 0;
 126 }