[2/2] libfdt: Rework/cleanup fdt_next_tag()
David Gibson
david at gibson.dropbear.id.au
Fri Feb 6 14:03:24 EST 2009
Currently, callers of fdt_next_tag() must usually follow the call with
some sort of call to fdt_offset_ptr() to verify that the blob isn't
truncated in the middle of the tag data they're going to process.
This is a bit silly, since fdt_next_tag() generally has to call
fdt_offset_ptr() on at least some of the data following the tag for
its own operation.
This patch alters fdt_next_tag() to always use fdt_offset_ptr() to
verify the data between its starting offset and the offset it returns
in nextoffset. This simplifies fdt_get_property() which no longer has
to verify itself that the property data is all present.
At the same time, I neaten and clarify the error handling for
fdt_next_tag(). Previously, fdt_next_tag() could return -1 instead of
a tag value in some circumstances - which almost none of the callers
checked for. Also, fdt_next_tag() could return FDT_END either because
it encountered an FDT_END tag, or because it reached the end of the
structure block - no way was provided to tell between these cases.
With this patch, fdt_next_tag() always returns FDT_END with a negative
value in nextoffset for an error. This means the several places which
loop looking for FDT_END will still work correctly - they only need to
check for errors at the end. The errors which fdt_next_tag() can
report are:
- -FDT_ERR_TRUNCATED if it reached the end of the structure
block instead of finding a tag.
- -FDT_BADSTRUCTURE if a bad tag was encountered, or if the
tag data couldn't be verified with fdt_offset_ptr().
This patch also updates the callers of fdt_next_tag(), where
appropriate, to make use of the new error reporting.
Finally, the prototype for the long gone _fdt_next_tag() is removed
from libfdt_internal.h.
Signed-off-by: David Gibson <david at gibson.dropbear.id.au>
---
libfdt/fdt.c | 46 +++++++++++++++++++++++++++++-----------------
libfdt/fdt_ro.c | 33 +++++++++------------------------
libfdt/fdt_rw.c | 2 ++
libfdt/fdt_sw.c | 9 ++++-----
libfdt/libfdt_internal.h | 1 -
5 files changed, 44 insertions(+), 47 deletions(-)
Index: dtc/libfdt/fdt.c
===================================================================
--- dtc.orig/libfdt/fdt.c 2009-02-06 13:47:44.000000000 +1100
+++ dtc/libfdt/fdt.c 2009-02-06 13:47:55.000000000 +1100
@@ -90,42 +90,53 @@ const void *fdt_offset_ptr(const void *f
return p;
}
-uint32_t fdt_next_tag(const void *fdt, int offset, int *nextoffset)
+uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
{
const uint32_t *tagp, *lenp;
uint32_t tag;
+ int offset = startoffset;
const char *p;
- if (offset % FDT_TAGSIZE)
- return -1;
-
+ *nextoffset = -FDT_ERR_TRUNCATED;
tagp = fdt_offset_ptr(fdt, offset, FDT_TAGSIZE);
- if (! tagp)
+ if (!tagp)
return FDT_END; /* premature end */
tag = fdt32_to_cpu(*tagp);
offset += FDT_TAGSIZE;
+ *nextoffset = -FDT_ERR_BADSTRUCTURE;
switch (tag) {
case FDT_BEGIN_NODE:
/* skip name */
do {
p = fdt_offset_ptr(fdt, offset++, 1);
} while (p && (*p != '\0'));
- if (! p)
- return FDT_END;
+ if (!p)
+ return FDT_END; /* premature end */
break;
+
case FDT_PROP:
lenp = fdt_offset_ptr(fdt, offset, sizeof(*lenp));
- if (! lenp)
- return FDT_END;
- /* skip name offset, length and value */
- offset += 2*FDT_TAGSIZE + fdt32_to_cpu(*lenp);
+ if (!lenp)
+ return FDT_END; /* premature end */
+ /* skip-name offset, length and value */
+ offset += sizeof(struct fdt_property) - FDT_TAGSIZE
+ + fdt32_to_cpu(*lenp);
+ break;
+
+ case FDT_END:
+ case FDT_END_NODE:
+ case FDT_NOP:
break;
+
+ default:
+ return FDT_END;
}
- if (nextoffset)
- *nextoffset = FDT_TAGALIGN(offset);
+ if (!fdt_offset_ptr(fdt, startoffset, offset - startoffset))
+ return FDT_END; /* premature end */
+ *nextoffset = FDT_TAGALIGN(offset);
return tag;
}
@@ -167,10 +178,11 @@ int fdt_next_node(const void *fdt, int o
break;
case FDT_END:
- return -FDT_ERR_NOTFOUND;
-
- default:
- return -FDT_ERR_BADSTRUCTURE;
+ if ((nextoffset >= 0)
+ || ((nextoffset == -FDT_ERR_TRUNCATED) && !depth))
+ return -FDT_ERR_NOTFOUND;
+ else
+ return nextoffset;
}
} while (tag != FDT_BEGIN_NODE);
Index: dtc/libfdt/fdt_rw.c
===================================================================
--- dtc.orig/libfdt/fdt_rw.c 2009-02-06 13:47:44.000000000 +1100
+++ dtc/libfdt/fdt_rw.c 2009-02-06 13:47:55.000000000 +1100
@@ -406,6 +406,8 @@ int fdt_open_into(const void *fdt, void
struct_size = 0;
while (fdt_next_tag(fdt, struct_size, &struct_size) != FDT_END)
;
+ if (struct_size < 0)
+ return struct_size;
}
if (!_fdt_blocks_misordered(fdt, mem_rsv_size, struct_size)) {
Index: dtc/libfdt/fdt_sw.c
===================================================================
--- dtc.orig/libfdt/fdt_sw.c 2009-02-06 13:47:44.000000000 +1100
+++ dtc/libfdt/fdt_sw.c 2009-02-06 13:47:55.000000000 +1100
@@ -82,7 +82,7 @@ static void *_fdt_grab_space(void *fdt,
return NULL;
fdt_set_size_dt_struct(fdt, offset + len);
- return fdt_offset_ptr_w(fdt, offset, len);
+ return _fdt_offset_ptr_w(fdt, offset);
}
int fdt_create(void *buf, int bufsize)
@@ -237,18 +237,17 @@ int fdt_finish(void *fdt)
while ((tag = fdt_next_tag(fdt, offset, &nextoffset)) != FDT_END) {
if (tag == FDT_PROP) {
struct fdt_property *prop =
- fdt_offset_ptr_w(fdt, offset, sizeof(*prop));
+ _fdt_offset_ptr_w(fdt, offset);
int nameoff;
- if (! prop)
- return -FDT_ERR_BADSTRUCTURE;
-
nameoff = fdt32_to_cpu(prop->nameoff);
nameoff += fdt_size_dt_strings(fdt);
prop->nameoff = cpu_to_fdt32(nameoff);
}
offset = nextoffset;
}
+ if (nextoffset < 0)
+ return nextoffset;
/* Finally, adjust the header */
fdt_set_totalsize(fdt, newstroffset + fdt_size_dt_strings(fdt));
Index: dtc/libfdt/fdt_ro.c
===================================================================
--- dtc.orig/libfdt/fdt_ro.c 2009-02-06 13:47:44.000000000 +1100
+++ dtc/libfdt/fdt_ro.c 2009-02-06 13:47:55.000000000 +1100
@@ -201,7 +201,6 @@ const struct fdt_property *fdt_get_prope
{
uint32_t tag;
const struct fdt_property *prop;
- int namestroff;
int offset, nextoffset;
int err;
@@ -216,38 +215,24 @@ const struct fdt_property *fdt_get_prope
tag = fdt_next_tag(fdt, offset, &nextoffset);
switch (tag) {
case FDT_END:
- err = -FDT_ERR_TRUNCATED;
+ if (nextoffset < 0)
+ err = nextoffset;
+ else
+ /* FDT_END tag with unclosed nodes */
+ err = -FDT_ERR_BADSTRUCTURE;
goto fail;
- case FDT_BEGIN_NODE:
- case FDT_END_NODE:
- case FDT_NOP:
- break;
-
case FDT_PROP:
- err = -FDT_ERR_BADSTRUCTURE;
- prop = fdt_offset_ptr(fdt, offset, sizeof(*prop));
- if (! prop)
- goto fail;
- namestroff = fdt32_to_cpu(prop->nameoff);
- if (_fdt_string_eq(fdt, namestroff, name, namelen)) {
+ prop = _fdt_offset_ptr(fdt, offset);
+ if (_fdt_string_eq(fdt, fdt32_to_cpu(prop->nameoff),
+ name, namelen)) {
/* Found it! */
- int len = fdt32_to_cpu(prop->len);
- prop = fdt_offset_ptr(fdt, offset,
- sizeof(*prop)+len);
- if (! prop)
- goto fail;
-
if (lenp)
- *lenp = len;
+ *lenp = fdt32_to_cpu(prop->len);
return prop;
}
break;
-
- default:
- err = -FDT_ERR_BADSTRUCTURE;
- goto fail;
}
} while ((tag != FDT_BEGIN_NODE) && (tag != FDT_END_NODE));
Index: dtc/libfdt/libfdt_internal.h
===================================================================
--- dtc.orig/libfdt/libfdt_internal.h 2009-02-06 13:47:44.000000000 +1100
+++ dtc/libfdt/libfdt_internal.h 2009-02-06 13:47:55.000000000 +1100
@@ -62,7 +62,6 @@
return err; \
}
-uint32_t _fdt_next_tag(const void *fdt, int startoffset, int *nextoffset);
int _fdt_check_node_offset(const void *fdt, int offset);
const char *_fdt_find_string(const char *strtab, int tabsize, const char *s);
int _fdt_node_end_offset(void *fdt, int nodeoffset);
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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