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[efi] Install a device tree for the booted OS, if available

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If we have a device tree available (e.g. because the user has
explicitly downloaded a device tree using the "fdt" command), then
provide it to the booted operating system as an EFI configuration
table.

Since x86 does not typically use device trees, we create weak symbols
for efi_fdt_install() and efi_fdt_uninstall() to avoid dragging FDT
support into all x86 UEFI binaries.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2025-03-28 14:20:44 +00:00
parent 761f43ce12
commit b20f506a72
3 changed files with 127 additions and 0 deletions
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82
src/interface/efi/efi_fdt.c
View File

@@ -24,9 +24,12 @@
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <string.h>
#include <byteswap.h>
#include <ipxe/fdt.h>
#include <ipxe/init.h>
#include <ipxe/efi/efi.h>
#include <ipxe/efi/efi_table.h>
#include <ipxe/efi/efi_fdt.h>
#include <ipxe/efi/Guid/Fdt.h>
/** @file
@@ -76,3 +79,82 @@ static void efi_fdt_init ( void ) {
struct init_fn efi_fdt_init_fn __init_fn ( INIT_EARLY ) = {
.initialise = efi_fdt_init,
};
/**
* Determine length of EFI Flattened Device Tree
*
* @v data Configuration table data (presumed valid)
* @ret len Length of table
*/
static size_t efi_fdt_len ( const void *data ) {
const struct fdt_header *hdr = data;
return be32_to_cpu ( hdr->totalsize );
}
/** EFI Flattened Device Tree table type */
static struct efi_table efi_fdt_table = {
.guid = &efi_fdt_table_guid,
.len = efi_fdt_len,
};
/** EFI Flattened Device Tree table backup */
static void *efi_fdt_backup;
/** EFI Flattened Device Tree installed table */
static struct fdt_header *efi_fdt_installed;
/**
* Install EFI Flattened Device Tree table
*
* @ret rc Return status code
*/
int efi_fdt_install ( void ) {
int rc;
/* Create device tree */
if ( ( rc = fdt_create ( &efi_fdt_installed ) ) != 0 ) {
DBGC ( &efi_fdt, "EFI_FDT could not install: %s\n",
strerror ( rc ) );
goto err_create;
}
/* Install table */
if ( ( rc = efi_install_table ( &efi_fdt_table, efi_fdt_installed,
&efi_fdt_backup ) ) != 0 ) {
DBGC ( &efi_fdt, "EFIFDT could not install: %s\n",
strerror ( rc ) );
goto err_install;
}
return 0;
efi_uninstall_table ( &efi_fdt_table, &efi_fdt_backup );
err_install:
fdt_remove ( efi_fdt_installed );
err_create:
return rc;
}
/**
* Uninstall EFI Flattened Device Tree table
*
* @ret rc Return status code
*/
int efi_fdt_uninstall ( void ) {
int rc;
/* Uninstall table */
if ( ( rc = efi_uninstall_table ( &efi_fdt_table,
&efi_fdt_backup ) ) != 0 ) {
DBGC ( &efi_fdt, "EFIFDT could not %sinstall: %s\n",
( efi_fdt_backup ? "re" : "un" ), strerror ( rc ) );
/* Leak memory: there is nothing else we can do */
return rc;
}
/* Remove table */
fdt_remove ( efi_fdt_installed );
return 0;
}