Hi Stefano,
On 11/9/18 9:38 PM, Stefano Stabellini wrote:
On Fri, 9 Nov 2018, Julien Grall wrote:
Hi,
On 02/11/2018 23:44, Stefano Stabellini wrote:
Make sure to only look for multiboot compatible nodes only under
/chosen, not under any other paths (depth <= 3).
Signed-off-by: Stefano Stabellini <stefa...@xilinx.com>
---
Changes in v6:
- do not proceed if fdt_get_path returns error != -FDT_ERR_NOSPACE
- remove sizeof, use hardcoded value
Changes in v5:
- add patch
- add check on return value of fdt_get_path
---
xen/arch/arm/bootfdt.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
index 8eba42c..a42fe87 100644
--- a/xen/arch/arm/bootfdt.c
+++ b/xen/arch/arm/bootfdt.c
@@ -173,7 +173,15 @@ static void __init process_multiboot_node(const void
*fdt, int node,
bootmodule_kind kind;
paddr_t start, size;
const char *cmdline;
- int len;
+ int len = 8; /* sizeof "/chosen" */
+ char path[8];
+ int ret;
+
+ /* Check that the node is under "chosen" */
+ ret = fdt_get_path(fdt, node, path, len);
+ if ( (ret != 0 && ret != -FDT_ERR_NOSPACE) ||
I don't understand why you specifically check for -FDT_ERR_NOSPACE here.
Looking at fdt_get_path(...) there are case where the function may return
-FDT_ERR_NOSPACE yet not filling up path. So you would end up to compare
garbage.
I am explicitely checking for -FDT_ERR_NOSPACE because it is a valid
condition in this case: -FDT_ERR_NOSPACE is returned where `path' is not
big enough to contain the full device tree path. It is OK and expected,
given that path is only 8 chars long. So, in case of -FDT_ERR_NOSPACE,
we should continue and do the comparison with "/chosen". For other
errors we should return.
Let's take an example with a path called /deadbeef. This will not hold
in the variable path. Do you agree that fdt_get_path will return
-FDT_ERR_NO_SPACE in that case?
AFAIU the function fdt_get_path, the buffer will contain the character
/ followed by garbage as '\0' is only added in successful path.
This also fit with the description of fdt_get_path when
-FDT_ERR_NO_SPACE. It does not promise you the buffer will contain
anything. It only tells you that the path on the given node will not fit
in the buffer.
So I still don't think you can assume the behavior you described above.
Cheers,
--
Julien Grall
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