[XEN v5 02/10] xen/arm: Typecast the DT values into paddr_t

[Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>]

The DT functions (dt_read_number(), device_tree_get_reg(), fdt_get_mem_rsv())
currently accept or return 64-bit values.

In future when we support 32-bit physical address, these DT functions are
expected to accept/return 32-bit or 64-bit values (depending on the width of
physical address). Also, we wish to detect if any truncation has occurred
(i.e. while parsing 32-bit physical addresses from 64-bit values read from DT).

device_tree_get_reg() should now be able to return paddr_t. This is invoked by
various callers to get DT address and size.

For fdt_get_mem_rsv(), we have introduced a wrapper named
fdt_get_mem_rsv_paddr() which will invoke fdt_get_mem_rsv() and translate
uint64_t to paddr_t. The reason being we cannot modify fdt_get_mem_rsv() as it
has been imported from external source.

For dt_read_number(), we have also introduced a wrapper named dt_read_paddr()
dt_read_paddr() to read physical addresses. We chose not to modify the original
function as it is used in places where it needs to specifically read 64-bit
values from dt (For e.g. dt_property_read_u64()).

Xen prints warning when it detects truncation in cases where it is not able to
return error.

Also, replaced u32/u64 with uint32_t/uint64_t in the functions touched
by the code changes.

Also, initialized variables to fix the warning "-Werror=maybe-uninitialized".

Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
---

Changes from

v1 - 1. Dropped "[XEN v1 2/9] xen/arm: Define translate_dt_address_size() for 
the translation between u64 and paddr_t" and
"[XEN v1 4/9] xen/arm: Use translate_dt_address_size() to translate between 
device tree addr/size and paddr_t", instead
this approach achieves the same purpose.

2. No need to check for truncation while converting values from u64 to paddr_t.

v2 - 1. Use "( (dt_start >> (PADDR_SHIFT - 1)) > 1 )" to detect truncation.
2. Introduced libfdt_xen.h to implement fdt_get_mem_rsv_paddr
3. Logged error messages in case truncation is detected.

v3 - 1. Renamed libfdt_xen.h to libfdt-xen.h.
2. Replaced u32/u64 with uint32_t/uint64_t
3. Use "(paddr_t)val != val" to check for truncation.
4. Removed the alias "#define PADDR_SHIFT PADDR_BITS". 

v4 - 1. Added a WARN() when truncation is detected.
2. Always check the return value of fdt_get_mem_rsv().

 xen/arch/arm/bootfdt.c              | 48 +++++++++++++++++++------
 xen/arch/arm/domain_build.c         |  2 +-
 xen/arch/arm/include/asm/setup.h    |  4 +--
 xen/arch/arm/setup.c                | 18 +++++-----
 xen/arch/arm/smpboot.c              |  2 +-
 xen/include/xen/device_tree.h       | 23 ++++++++++++
 xen/include/xen/libfdt/libfdt-xen.h | 55 +++++++++++++++++++++++++++++
 7 files changed, 129 insertions(+), 23 deletions(-)
 create mode 100644 xen/include/xen/libfdt/libfdt-xen.h

diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
index 0085c28d74..ac8148da55 100644
--- a/xen/arch/arm/bootfdt.c
+++ b/xen/arch/arm/bootfdt.c
@@ -11,7 +11,7 @@
 #include <xen/efi.h>
 #include <xen/device_tree.h>
 #include <xen/lib.h>
-#include <xen/libfdt/libfdt.h>
+#include <xen/libfdt/libfdt-xen.h>
 #include <xen/sort.h>
 #include <xsm/xsm.h>
 #include <asm/setup.h>
@@ -52,11 +52,37 @@ static bool __init device_tree_node_compatible(const void 
*fdt, int node,
     return false;
 }
 
-void __init device_tree_get_reg(const __be32 **cell, u32 address_cells,
-                                u32 size_cells, u64 *start, u64 *size)
+void __init device_tree_get_reg(const __be32 **cell, uint32_t address_cells,
+                                uint32_t size_cells, paddr_t *start,
+                                paddr_t *size)
 {
-    *start = dt_next_cell(address_cells, cell);
-    *size = dt_next_cell(size_cells, cell);
+    uint64_t dt_start, dt_size;
+
+    /*
+     * dt_next_cell will return uint64_t whereas paddr_t may not be 64-bit.
+     * Thus, there is an implicit cast from uint64_t to paddr_t.
+     */
+    dt_start = dt_next_cell(address_cells, cell);
+    dt_size = dt_next_cell(size_cells, cell);
+
+    if ( dt_start != (paddr_t)dt_start )
+    {
+        printk("Error: Physical address greater than max width supported\n");
+        WARN();
+    }
+
+    if ( dt_size != (paddr_t)dt_size )
+    {
+        printk("Error: Physical size greater than max width supported\n");
+        WARN();
+    }
+
+    /*
+     * Xen will truncate the address/size if it is greater than the maximum
+     * supported width and it will give an appropriate warning.
+     */
+    *start = dt_start;
+    *size = dt_size;
 }
 
 static int __init device_tree_get_meminfo(const void *fdt, int node,
@@ -326,7 +352,7 @@ static int __init process_chosen_node(const void *fdt, int 
node,
         printk("linux,initrd-start property has invalid length %d\n", len);
         return -EINVAL;
     }
-    start = dt_read_number((void *)&prop->data, dt_size_to_cells(len));
+    start = dt_read_paddr((void *)&prop->data, dt_size_to_cells(len));
 
     prop = fdt_get_property(fdt, node, "linux,initrd-end", &len);
     if ( !prop )
@@ -339,7 +365,7 @@ static int __init process_chosen_node(const void *fdt, int 
node,
         printk("linux,initrd-end property has invalid length %d\n", len);
         return -EINVAL;
     }
-    end = dt_read_number((void *)&prop->data, dt_size_to_cells(len));
+    end = dt_read_paddr((void *)&prop->data, dt_size_to_cells(len));
 
     if ( start >= end )
     {
@@ -593,10 +619,12 @@ static void __init early_print_info(void)
     nr_rsvd = fdt_num_mem_rsv(device_tree_flattened);
     for ( i = 0; i < nr_rsvd; i++ )
     {
-        paddr_t s, e;
-        if ( fdt_get_mem_rsv(device_tree_flattened, i, &s, &e) < 0 )
+        paddr_t s = 0, e = 0;
+
+        if ( fdt_get_mem_rsv_paddr(device_tree_flattened, i, &s, &e) < 0 )
             continue;
-        /* fdt_get_mem_rsv returns length */
+
+        /* fdt_get_mem_rsv_paddr returns length */
         e += s;
         printk(" RESVD[%u]: %"PRIpaddr" - %"PRIpaddr"\n", i, s, e);
     }
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index c8f08d8ee2..15c8bdd9e4 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -949,7 +949,7 @@ static int __init process_shm(struct domain *d, struct 
kernel_info *kinfo,
         BUG_ON(!prop);
         cells = (const __be32 *)prop->value;
         device_tree_get_reg(&cells, addr_cells, addr_cells, &pbase, &gbase);
-        psize = dt_read_number(cells, size_cells);
+        psize = dt_read_paddr(cells, size_cells);
         if ( !IS_ALIGNED(pbase, PAGE_SIZE) || !IS_ALIGNED(gbase, PAGE_SIZE) )
         {
             printk("%pd: physical address 0x%"PRIpaddr", or guest address 
0x%"PRIpaddr" is not suitably aligned.\n",
diff --git a/xen/arch/arm/include/asm/setup.h b/xen/arch/arm/include/asm/setup.h
index a926f30a2b..7b697d879e 100644
--- a/xen/arch/arm/include/asm/setup.h
+++ b/xen/arch/arm/include/asm/setup.h
@@ -157,8 +157,8 @@ const char *boot_module_kind_as_string(bootmodule_kind 
kind);
 extern uint32_t hyp_traps_vector[];
 void init_traps(void);
 
-void device_tree_get_reg(const __be32 **cell, u32 address_cells,
-                         u32 size_cells, u64 *start, u64 *size);
+void device_tree_get_reg(const __be32 **cell, uint32_t address_cells,
+                         uint32_t size_cells, paddr_t *start, paddr_t *size);
 
 u32 device_tree_get_u32(const void *fdt, int node,
                         const char *prop_name, u32 dflt);
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 1f26f67b90..d2a3d8c340 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -29,7 +29,7 @@
 #include <xen/virtual_region.h>
 #include <xen/vmap.h>
 #include <xen/trace.h>
-#include <xen/libfdt/libfdt.h>
+#include <xen/libfdt/libfdt-xen.h>
 #include <xen/acpi.h>
 #include <xen/warning.h>
 #include <asm/alternative.h>
@@ -220,13 +220,13 @@ static void __init dt_unreserved_regions(paddr_t s, 
paddr_t e,
 
     for ( i = first; i < nr ; i++ )
     {
-        paddr_t r_s, r_e;
+        paddr_t r_s = 0, r_e = 0;
 
-        if ( fdt_get_mem_rsv(device_tree_flattened, i, &r_s, &r_e ) < 0 )
+        if ( fdt_get_mem_rsv_paddr(device_tree_flattened, i, &r_s, &r_e ) < 0 )
             /* If we can't read it, pretend it doesn't exist... */
             continue;
 
-        r_e += r_s; /* fdt_get_mem_rsv returns length */
+        r_e += r_s; /* fdt_get_mem_rsv_paddr returns length */
 
         if ( s < r_e && r_s < e )
         {
@@ -500,15 +500,15 @@ static paddr_t __init consider_modules(paddr_t s, paddr_t 
e,
 
     for ( ; i < mi->nr_mods + nr; i++ )
     {
-        paddr_t mod_s, mod_e;
+        paddr_t mod_s = 0, mod_e = 0;
 
-        if ( fdt_get_mem_rsv(device_tree_flattened,
-                             i - mi->nr_mods,
-                             &mod_s, &mod_e ) < 0 )
+        if ( fdt_get_mem_rsv_paddr(device_tree_flattened,
+                                   i - mi->nr_mods,
+                                   &mod_s, &mod_e ) < 0 )
             /* If we can't read it, pretend it doesn't exist... */
             continue;
 
-        /* fdt_get_mem_rsv returns length */
+        /* fdt_get_mem_rsv_paddr returns length */
         mod_e += mod_s;
 
         if ( s < mod_e && mod_s < e )
diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index 412ae22869..c15c177487 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -159,7 +159,7 @@ static void __init dt_smp_init_cpus(void)
             continue;
         }
 
-        addr = dt_read_number(prop, dt_n_addr_cells(cpu));
+        addr = dt_read_paddr(prop, dt_n_addr_cells(cpu));
 
         hwid = addr;
         if ( hwid != addr )
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 19a74909ce..11bda2fd3d 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -241,6 +241,29 @@ static inline u64 dt_read_number(const __be32 *cell, int 
size)
     return r;
 }
 
+/* Wrapper for dt_read_number() to return paddr_t (instead of uint64_t) */
+static inline paddr_t dt_read_paddr(const __be32 *cell, int size)
+{
+    uint64_t dt_r = 0;
+    paddr_t r;
+
+    dt_r = dt_read_number(cell, size);
+
+    if ( dt_r != (paddr_t)dt_r )
+    {
+        printk("Error: Physical address greater than max width supported\n");
+        WARN();
+    }
+
+    /*
+     * Xen will truncate the address/size if it is greater than the maximum
+     * supported width and it will give an appropriate warning.
+     */
+    r = dt_r;
+
+    return r;
+}
+
 /* Helper to convert a number of cells to bytes */
 static inline int dt_cells_to_size(int size)
 {
diff --git a/xen/include/xen/libfdt/libfdt-xen.h 
b/xen/include/xen/libfdt/libfdt-xen.h
new file mode 100644
index 0000000000..3296a368a6
--- /dev/null
+++ b/xen/include/xen/libfdt/libfdt-xen.h
@@ -0,0 +1,55 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-only
+ *
+ * xen/include/xen/libfdt/libfdt-xen.h
+ *
+ * Wrapper functions for device tree. This helps to convert dt values
+ * between uint64_t and paddr_t.
+ *
+ * Copyright (C) 2023, Advanced Micro Devices, Inc. All Rights Reserved.
+ */
+
+#ifndef LIBFDT_XEN_H
+#define LIBFDT_XEN_H
+
+#include <xen/libfdt/libfdt.h>
+
+static inline int fdt_get_mem_rsv_paddr(const void *fdt, int n,
+                                        paddr_t *address,
+                                        paddr_t *size)
+{
+    uint64_t dt_addr;
+    uint64_t dt_size;
+    int ret = 0;
+
+    ret = fdt_get_mem_rsv(fdt, n, &dt_addr, &dt_size);
+    if ( ret )
+        return ret;
+
+    if ( dt_addr != (paddr_t)dt_addr )
+    {
+        printk("Error: Physical address greater than max width supported\n");
+        return -FDT_ERR_MAX;
+    }
+
+    if ( dt_size != (paddr_t)dt_size )
+    {
+        printk("Error: Physical size greater than max width supported\n");
+        return -FDT_ERR_MAX;
+    }
+
+    *address = dt_addr;
+    *size = dt_size;
+
+    return ret;
+}
+
+#endif /* LIBFDT_XEN_H */
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.17.1