On 5/14/24 14:58, Mark Kettenis wrote:
Date: Tue, 14 May 2024 14:49:47 +0200
From: Heinrich Schuchardt <heinrich.schucha...@canonical.com>
Hi Heinrich,
On 4/26/24 17:47, Ilias Apalodimas wrote:
Hi Heinrich
On Fri, 26 Apr 2024 at 17:53, Heinrich Schuchardt
<heinrich.schucha...@canonical.com> wrote:
On 26.04.24 16:30, Ilias Apalodimas wrote:
Hi Heinrich,
On Fri, 26 Apr 2024 at 17:13, Heinrich Schuchardt
<heinrich.schucha...@canonical.com> wrote:
Provide a function to append a device_path to a list of device paths
that is separated by final end nodes.
Signed-off-by: Heinrich Schuchardt <heinrich.schucha...@canonical.com>
---
include/efi_loader.h | 3 +++
lib/efi_loader/efi_device_path.c | 31 +++++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/include/efi_loader.h b/include/efi_loader.h
index 9600941aa32..a7d7b8324f1 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -944,6 +944,9 @@ struct efi_load_option {
struct efi_device_path *efi_dp_from_lo(struct efi_load_option *lo,
const efi_guid_t *guid);
+struct efi_device_path *efi_dp_merge(const struct efi_device_path *dp1,
+ efi_uintn_t *size,
+ const struct efi_device_path *dp2);
struct efi_device_path *efi_dp_concat(const struct efi_device_path *dp1,
const struct efi_device_path *dp2,
bool split_end_node);
diff --git a/lib/efi_loader/efi_device_path.c b/lib/efi_loader/efi_device_path.c
index 46aa59b9e40..16cbe41d32f 100644
--- a/lib/efi_loader/efi_device_path.c
+++ b/lib/efi_loader/efi_device_path.c
@@ -270,6 +270,37 @@ struct efi_device_path *efi_dp_dup(const struct
efi_device_path *dp)
return ndp;
}
+/**
+ * efi_dp_merge() - Concatenate two device paths separated by final end node
+ *
+ * @dp1: first device path
+ * @size: pointer to length of @dp1, total size on return
+ * @dp2: second device path
+ *
+ * Return: concatenated device path or NULL
+ */
+struct efi_device_path *efi_dp_merge(const struct efi_device_path *dp1,
+ efi_uintn_t *size,
+ const struct efi_device_path *dp2)
+{
+ efi_uintn_t len, len1, len2;
+ struct efi_device_path *dp;
+ u8 *p;
+
+ len1 = *size;
+ len2 = efi_dp_size(dp2) + sizeof(END);
+ len = len1 + len2;
+ dp = efi_alloc(len);
+ if (!dp)
+ return NULL;
+ memcpy(dp, dp1, len1);
+ p = (u8 *)dp + len1;
+ memcpy(p, dp2, len2);
+ *size = len;
Can't we just use efi_dp_concat()?
efi_dp_concat cannot be used to put a device-path end-node in between
two device-paths that are concatenated. We need that separator in the
load options.
I am not sure I am following you. It's been a few years so please bear
with me until I manage to re-read that code and page it back to
memory.
What I remember though is that the format of the DP looks like this:
Loaded image DP - end node - initrd GUID DP (without and end node) -
initrd - end of device path.
So to jump from the special initrd GUID to the actual DP that contains
the initrd you need to do an efi_dp_next(). Also, efi_dp_concat() will
inject an end node with a DEVICE_PATH_SUB_TYPE_END type if the third
argument is 'true'.
What am I missing?
Let us assume
dp1 = /vmlinux/endnode/initrd/endnode
dp2 = /dtb/endnode
and we invoke dp_concat(dp1, dp2, true):
sz1 is calculated via the efi_dp_size() function which looks for the
*first* device-path end node.
sz1 = efi_dp_size(dp1) = sizeof(/vmlinux)
sz1 will not include initrd and its endnode.
So dp_concat(/vmlinux/endnode/initrd/endnode, /dtb/endnode, true)
will return:
/vmlinux/endnode/dtb/endnode
but in our boot option we want
/vmlinux/endnode/initrd/endnode/dtb/endnode
That makes me realize a potential flaw with the design of this boot
option. The concept of an initrd is Linux-specific, but the concept
of loading a DTB to pass along to an EFI image far less so. So how
would this work if I want to only pass the DTB? Would that be:
/vmlinux/endnode/endnode/dtb/endnode
Hello Mark,
We have a VenMedia() device path node with specific GUIDs for initrd and
dtb prefixed to these paths. See patch 03/14.
We don't rely on the position. So in your case:
/vmlinux/endnode/dtb/endnode
where the device path 'dtb' would consist of multiple nodes, e.g.:
VenMedia(EFI_FDT_GUID)/HD(1,GPT, ...)/\dir\filename.dtb
Best regards
Heinrich
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