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sysroot: Support for standard-conformance marker file

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Add support for standard-conformance marker file loader/entries.srel.

There might be implementations of boot loading infrastructure that are
also using the /loader/entries/ directory, but install files that do
not follow the [1] specification. In order to minimize confusion, a boot
loader implementation may place the file /loader/entries.srel next to the
/loader/entries/ directory containing the ASCII string type1 (followed
by a UNIX newline). Tools that need to determine whether an existing
directory implements the semantics described here may check for this
file and contents: if it exists and contains the mentioned string,
it shall assume a standards-compliant implementation is in place.
If it exists but contains a different string it shall assume other
semantics are implemented. If the file does not exist, no assumptions
should be made.

[1] https://uapi-group.org/specifications/specs/boot_loader_specification/#type-1-boot-loader-entry-keys
Signed-off-by: Igor Opaniuk <igor.opaniuk@foundries.io>

boot semantics

semantics
This commit is contained in:
Igor Opaniuk 2025-01-08 15:53:31 +01:00
parent 8e47955247
commit 04fd02ba6b
1 changed files with 54 additions and 0 deletions
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54
src/libostree/ostree-sysroot-deploy.c
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@ -2180,6 +2180,56 @@ install_deployment_kernel (OstreeSysroot *sysroot, int new_bootversion,
return TRUE;
}
/* Determine whether an existing directory implements the semantics described in
* https://uapi-group.org/specifications/specs/boot_loader_specification/#type-1-boot-loader-entry-keys
*/
static gboolean
is_bootconfig_type1_semantics (OstreeSysroot *sysroot, GCancellable *cancellable, GError **error)
{
struct stat stbuf;
if (!_ostree_sysroot_ensure_boot_fd (sysroot, error))
return FALSE;
if (!glnx_fstatat_allow_noent (sysroot->boot_fd, "loader/entries.srel", &stbuf,
AT_SYMLINK_NOFOLLOW, error))
return FALSE;
if (errno == ENOENT)
{
g_debug ("Didn't find loader/entries.srel file");
return FALSE;
}
else
{
/* Get semantics type by reading loader/entries.srel */
gsize len;
g_autofree char *type = glnx_file_get_contents_utf8_at (
sysroot->boot_fd, "loader/entries.srel", &len, cancellable, error);
if (type == NULL)
{
g_debug ("Invalid loader/entries.srel file");
return FALSE;
}
/* Remove trailing newline symbol if there is any */
type[strcspn (type, "\n")] = 0;
if (g_strcmp0 (type, "type1") == 0)
{
g_debug ("type1 semantics is found in loader/entries.srel file");
return TRUE;
}
else
{
g_debug ("Unsupported semantics type ('%s') in loader/entries.srel file", type);
return FALSE;
}
}
return FALSE;
}
/* We generate the symlink on disk, then potentially do a syncfs() to ensure
* that it (and everything else we wrote) has hit disk. Only after that do we
* rename it into place.
@ -2505,6 +2555,7 @@ write_deployments_bootswap (OstreeSysroot *self, GPtrArray *new_deployments,
*/
struct stat stbuf;
gboolean loader_link = FALSE;
gboolean force_type1_semantics = is_bootconfig_type1_semantics (self, cancellable, error);
if (!glnx_fstatat_allow_noent (self->sysroot_fd, "boot/loader", &stbuf, AT_SYMLINK_NOFOLLOW,
error))
return FALSE;
@ -2528,6 +2579,9 @@ write_deployments_bootswap (OstreeSysroot *self, GPtrArray *new_deployments,
else
return FALSE;
if (force_type1_semantics && loader_link)
return glnx_throw_errno_prefix (error, "type1 semantics, but boot/loader is symlink");
if (loader_link)
{
/* Default and when loader is a link is to swap links */