On Mon, Jan 04, 2021 at 09:39:00AM +0100, Sebastian Huber wrote:
> Hello,
>
> I get a compile error with GCC 11 in fdtdump.c:
>
> In file included from fdtdump.c:14:
> fdtdump.c: In function ‘main’:
> libfdt/libfdt.h:256:28: error: array subscript ‘struct fdt_header[0]’ is
> partly outside array bounds of ‘unsigned char[4]’ [-Werror=array-bounds]
> 256 | fdth->name = cpu_to_fdt32(val); \
> | ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
> libfdt/libfdt.h:258:1: note: in expansion of macro ‘fdt_set_hdr_’
> 258 | fdt_set_hdr_(magic);
> | ^~~~~~~~~~~~
> fdtdump.c:216:31: note: while referencing ‘smagic’
> 216 | unsigned char smagic[FDT_MAGIC_SIZE];
> | ^~~~~~
> cc1: all warnings being treated as errors
Ah, I think I see what's going wrong here. I don't have easy access
to gcc 11 to test with, so can you give this draft patch a test:
From 6307635b052b55cba6970ae3fb70f33259c572a4 Mon Sep 17 00:00:00 2001
From: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 6 Jan 2021 14:52:26 +1100
Subject: [PATCH] fdtdump: Fix gcc11 warning
In one place, fdtdump abuses fdt_set_magic(), passing it just a small char
array instead of the full fdt header it expects. That's relying on the
fact that in fact fdt_set_magic() will only actually access the first 4
bytes of the buffer.
This trips a new warning in GCC 11 - and it's entirely possible it was
always UB. So, don't do that.
Signed-off-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
---
fdtdump.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fdtdump.c b/fdtdump.c
index 9613bef..d9fb374 100644
--- a/fdtdump.c
+++ b/fdtdump.c
@@ -217,7 +217,7 @@ int main(int argc, char *argv[])
char *p = buf;
char *endp = buf + len;
- fdt_set_magic(smagic, FDT_MAGIC);
+ fdt32_st(smagic, FDT_MAGIC);
/* poor man's memmem */
while ((endp - p) >= FDT_MAGIC_SIZE) {
--
2.29.2
--
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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