x86/jailhouse: Improve setup data version comparison

Soon, setup_data will contain information on passed-through platform
UARTs. This requires some preparational work for the sanity check of the
header and the check of the version.

Use the following strategy:

  1. Ensure that the header declares at least enough space for the
     version and the compatible_version as it must hold that fields for
     any version. The location and semantics of header+version fields
     will never change.

  2. Copy over data -- as much as as possible. The length is either
     limited by the header length or the length of setup_data.

  3. Things are now in place -- sanity check if the header length
     complies the actual version.

For future versions of the setup_data, only step 3 requires alignment.

Signed-off-by: Ralf Ramsauer <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Jan Kiszka <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: Juergen Gross <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

1 files changed, 13 insertions, 9 deletions

diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index c895df5482c5..43be437c9c71 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -139,15 +139,19 @@ struct boot_e820_entry {
  * setup data structure.
  */
 struct jailhouse_setup_data {
-	__u16	version;
-	__u16	compatible_version;
-	__u16	pm_timer_address;
-	__u16	num_cpus;
-	__u64	pci_mmconfig_base;
-	__u32	tsc_khz;
-	__u32	apic_khz;
-	__u8	standard_ioapic;
-	__u8	cpu_ids[255];
+	struct {
+		__u16	version;
+		__u16	compatible_version;
+	} __attribute__((packed)) hdr;
+	struct {
+		__u16	pm_timer_address;
+		__u16	num_cpus;
+		__u64	pci_mmconfig_base;
+		__u32	tsc_khz;
+		__u32	apic_khz;
+		__u8	standard_ioapic;
+		__u8	cpu_ids[255];
+	} __attribute__((packed)) v1;
 } __attribute__((packed));
 
 /* The so-called "zeropage" */