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[efi] Create a copy of the system flattened device tree, if present

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EFI configuration tables may be freed at any time, and there is no way
to be notified when the table becomes invalidated.  Create a copy of
the system flattened device tree (if present), so that we do not risk
being left with an invalid pointer.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2025-03-28 14:10:55 +00:00
parent 3860313dd5
commit 666929e311
3 changed files with 15 additions and 5 deletions
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3
src/core/fdt.c
View File

@@ -456,8 +456,7 @@ int fdt_mac ( struct fdt *fdt, unsigned int offset,
* @v max_len Maximum device tree length * @v max_len Maximum device tree length
* @ret rc Return status code * @ret rc Return status code
*/ */
int fdt_parse ( struct fdt *fdt, const struct fdt_header *hdr, int fdt_parse ( struct fdt *fdt, struct fdt_header *hdr, size_t max_len ) {
size_t max_len ) {
const uint8_t *end; const uint8_t *end;
/* Sanity check */ /* Sanity check */

6
src/include/ipxe/fdt.h
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@@ -78,9 +78,9 @@ struct fdt {
/** Tree data */ /** Tree data */
union { union {
/** Tree header */ /** Tree header */
const struct fdt_header *hdr; struct fdt_header *hdr;
/** Raw data */ /** Raw data */
const void *raw; void *raw;
}; };
/** Length of tree */ /** Length of tree */
size_t len; size_t len;
@@ -107,7 +107,7 @@ extern int fdt_u64 ( struct fdt *fdt, unsigned int offset, const char *name,
uint64_t *value ); uint64_t *value );
extern int fdt_mac ( struct fdt *fdt, unsigned int offset, extern int fdt_mac ( struct fdt *fdt, unsigned int offset,
struct net_device *netdev ); struct net_device *netdev );
extern int fdt_parse ( struct fdt *fdt, const struct fdt_header *hdr, extern int fdt_parse ( struct fdt *fdt, struct fdt_header *hdr,
size_t max_len ); size_t max_len );
#endif /* _IPXE_FDT_H */ #endif /* _IPXE_FDT_H */

11
src/interface/efi/efi_fdt.c
View File

@@ -44,6 +44,8 @@ EFI_USE_TABLE ( FDT_TABLE, &efi_fdt, 0 );
* *
*/ */
static void efi_fdt_init ( void ) { static void efi_fdt_init ( void ) {
EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
EFI_STATUS efirc;
int rc; int rc;
/* Do nothing if no configuration table is present */ /* Do nothing if no configuration table is present */
@@ -59,6 +61,15 @@ static void efi_fdt_init ( void ) {
strerror ( rc ) ); strerror ( rc ) );
return; return;
} }
/* Create copy, since table may be removed at any time */
if ( ( efirc = bs->AllocatePool ( EfiBootServicesData, sysfdt.len,
&sysfdt.raw ) ) != 0 ) {
DBGC ( &efi_fdt, "EFIFDT could not create copy\n" );
sysfdt.len = 0;
return;
}
memcpy ( sysfdt.raw, efi_fdt, sysfdt.len );
} }
/** EFI Flattened Device Tree initialisation function */ /** EFI Flattened Device Tree initialisation function */