Commits 6dcb8ba4 "libfdt: Add helpers for accessing unaligned words"
introduced changes to support unaligned reads for ARM platforms and
11738cf01f15 "libfdt: Don't use memcpy to handle unaligned reads on ARM"
improved the performance of these helpers.
On further discussion, while there are potential cases where we could be
used on platforms that do not fixup unaligned reads for us, making this
choice the default is very expensive in terms of binary size and access
time. To address this, introduce and use new _fdt{32,64}_ld functions
that call fdt{32,64}_to_cpu() as was done prior to the above mentioned
commits. Leave the existing load functions as unaligned-safe and
include comments in both cases.
Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
Signed-off-by: Tom Rini <trini@xxxxxxxxxxxx>
---
Changes in v2:
- Move the new internal functions to libfdt_internal.h (per Rob).
- Drop change to fdtget.c as it shouldn't use internal helpers, only
exposed API.
- Add Rob's Reviewed-by
---
libfdt/fdt_ro.c | 20 ++++++++++----------
libfdt/libfdt.h | 8 +++-----
libfdt/libfdt_internal.h | 17 +++++++++++++++++
3 files changed, 30 insertions(+), 15 deletions(-)
diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index 91cc6fefe374..414b417362a8 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -181,8 +181,8 @@ int fdt_get_mem_rsv(const void *fdt, int n, uint64_t *address, uint64_t *size)
if (!can_assume(VALID_INPUT) && !re)
return -FDT_ERR_BADOFFSET;
- *address = fdt64_ld(&re->address);
- *size = fdt64_ld(&re->size);
+ *address = _fdt64_ld(&re->address);
+ *size = _fdt64_ld(&re->size);
return 0;
}
@@ -192,7 +192,7 @@ int fdt_num_mem_rsv(const void *fdt)
const struct fdt_reserve_entry *re;
for (i = 0; (re = fdt_mem_rsv(fdt, i)) != NULL; i++) {
- if (fdt64_ld(&re->size) == 0)
+ if (_fdt64_ld(&re->size) == 0)
return i;
}
return -FDT_ERR_TRUNCATED;
@@ -370,7 +370,7 @@ static const struct fdt_property *fdt_get_property_by_offset_(const void *fdt,
prop = fdt_offset_ptr_(fdt, offset);
if (lenp)
- *lenp = fdt32_ld(&prop->len);
+ *lenp = _fdt32_ld(&prop->len);
return prop;
}
@@ -408,7 +408,7 @@ static const struct fdt_property *fdt_get_property_namelen_(const void *fdt,
offset = -FDT_ERR_INTERNAL;
break;
}
- if (fdt_string_eq_(fdt, fdt32_ld(&prop->nameoff),
+ if (fdt_string_eq_(fdt, _fdt32_ld(&prop->nameoff),
name, namelen)) {
if (poffset)
*poffset = offset;
@@ -461,7 +461,7 @@ const void *fdt_getprop_namelen(const void *fdt, int nodeoffset,
/* Handle realignment */
if (!can_assume(LATEST) && fdt_version(fdt) < 0x10 &&
- (poffset + sizeof(*prop)) % 8 && fdt32_ld(&prop->len) >= 8)
+ (poffset + sizeof(*prop)) % 8 && _fdt32_ld(&prop->len) >= 8)
return prop->data + 4;
return prop->data;
}
@@ -479,7 +479,7 @@ const void *fdt_getprop_by_offset(const void *fdt, int offset,
int namelen;
if (!can_assume(VALID_INPUT)) {
- name = fdt_get_string(fdt, fdt32_ld(&prop->nameoff),
+ name = fdt_get_string(fdt, _fdt32_ld(&prop->nameoff),
&namelen);
if (!name) {
if (lenp)
@@ -488,13 +488,13 @@ const void *fdt_getprop_by_offset(const void *fdt, int offset,
}
*namep = name;
} else {
- *namep = fdt_string(fdt, fdt32_ld(&prop->nameoff));
+ *namep = fdt_string(fdt, _fdt32_ld(&prop->nameoff));
}
}
/* Handle realignment */
if (!can_assume(LATEST) && fdt_version(fdt) < 0x10 &&
- (offset + sizeof(*prop)) % 8 && fdt32_ld(&prop->len) >= 8)
+ (offset + sizeof(*prop)) % 8 && _fdt32_ld(&prop->len) >= 8)
return prop->data + 4;
return prop->data;
}
@@ -519,7 +519,7 @@ uint32_t fdt_get_phandle(const void *fdt, int nodeoffset)
return 0;
}
- return fdt32_ld(php);
+ return _fdt32_ld(php);
}
const char *fdt_get_alias_namelen(const void *fdt,
diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index b600c8d6dd41..3f36ed6d690f 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -126,12 +126,10 @@ static inline void *fdt_offset_ptr_w(void *fdt, int offset, int checklen)
uint32_t fdt_next_tag(const void *fdt, int offset, int *nextoffset);
/*
- * Alignment helpers:
- * These helpers access words from a device tree blob. They're
- * built to work even with unaligned pointers on platforms (ike
- * ARM) that don't like unaligned loads and stores
+ * External helpers to access words from a device tree blob. These functions
+ * work in a manner that is safe on platforms that do not handle unaligned
+ * memory accesses and need special care in those cases.
*/
-
static inline uint32_t fdt32_ld(const fdt32_t *p)
{
const uint8_t *bp = (const uint8_t *)p;
diff --git a/libfdt/libfdt_internal.h b/libfdt/libfdt_internal.h
index d4e0bd49c037..785b8b45ad1c 100644
--- a/libfdt/libfdt_internal.h
+++ b/libfdt/libfdt_internal.h
@@ -46,6 +46,23 @@ static inline struct fdt_reserve_entry *fdt_mem_rsv_w_(void *fdt, int n)
return (void *)(uintptr_t)fdt_mem_rsv_(fdt, n);
}
+/*
+ * Internal helpers to access words from a device tree blob. Assume that we
+ * are on a platform where unaligned memory reads will be handled in a graceful
+ * manner and that we do not need to ensure our reads are aligned. If this is
+ * not the case there are _unaligned versions of these functions that follow
+ * and can be used.
+ */
+static inline uint32_t _fdt32_ld(const fdt32_t *p)
+{
+ return fdt32_to_cpu(*p);
+}
+
+static inline uint64_t _fdt64_ld(const fdt64_t *p)
+{
+ return fdt64_to_cpu(*p);
+}
+
#define FDT_SW_MAGIC (~FDT_MAGIC)
/**********************************************************************/
--
2.17.1
