Make systemd-boot compliant with the Linux Boot / EFI Handover Protocol

The current implementation copied the *complete* header to boot_params,
thus making the kernel ignore many of the fields.

As mentioned in the code comment for the sentinel variable in
bootparam.h a bootloader should only copy the setup_header, set some
fields in boot_params and zero out anything else.

This change makes systemd-boot (mostly) compliant with the Linux Boot
Protocol and the EFI Handover Protocol described in bootparam.h and
Documentation/boot.txt to fix various issues:

- Secure boot not being detected corretly by Linux (#11717)
- tboot error message / warning on boot (#11717)
- Strange purple text color when booting in qemu with OVMF
- Hopefully even more ...

2 files changed, 107 insertions, 69 deletions

diff --git a/src/boot/efi/linux.c b/src/boot/efi/linux.c
index 33d51dbd72..ad26cc510e 100644
--- a/src/boot/efi/linux.c
+++ b/src/boot/efi/linux.c
@@ -6,66 +6,22 @@
 #include "linux.h"
 #include "util.h"
 
-#define SETUP_MAGIC             0x53726448      /* "HdrS" */
-struct SetupHeader {
-        UINT8 boot_sector[0x01f1];
-        UINT8 setup_secs;
-        UINT16 root_flags;
-        UINT32 sys_size;
-        UINT16 ram_size;
-        UINT16 video_mode;
-        UINT16 root_dev;
-        UINT16 signature;
-        UINT16 jump;
-        UINT32 header;
-        UINT16 version;
-        UINT16 su_switch;
-        UINT16 setup_seg;
-        UINT16 start_sys;
-        UINT16 kernel_ver;
-        UINT8 loader_id;
-        UINT8 load_flags;
-        UINT16 movesize;
-        UINT32 code32_start;
-        UINT32 ramdisk_start;
-        UINT32 ramdisk_len;
-        UINT32 bootsect_kludge;
-        UINT16 heap_end;
-        UINT8 ext_loader_ver;
-        UINT8 ext_loader_type;
-        UINT32 cmd_line_ptr;
-        UINT32 ramdisk_max;
-        UINT32 kernel_alignment;
-        UINT8 relocatable_kernel;
-        UINT8 min_alignment;
-        UINT16 xloadflags;
-        UINT32 cmdline_size;
-        UINT32 hardware_subarch;
-        UINT64 hardware_subarch_data;
-        UINT32 payload_offset;
-        UINT32 payload_length;
-        UINT64 setup_data;
-        UINT64 pref_address;
-        UINT32 init_size;
-        UINT32 handover_offset;
-} __attribute__((packed));
-
 #ifdef __x86_64__
-typedef VOID(*handover_f)(VOID *image, EFI_SYSTEM_TABLE *table, struct SetupHeader *setup);
-static VOID linux_efi_handover(EFI_HANDLE image, struct SetupHeader *setup) {
+typedef VOID(*handover_f)(VOID *image, EFI_SYSTEM_TABLE *table, struct boot_params *params);
+static VOID linux_efi_handover(EFI_HANDLE image, struct boot_params *params) {
         handover_f handover;
 
         asm volatile ("cli");
-        handover = (handover_f)((UINTN)setup->code32_start + 512 + setup->handover_offset);
-        handover(image, ST, setup);
+        handover = (handover_f)((UINTN)params->hdr.code32_start + 512 + params->hdr.handover_offset);
+        handover(image, ST, params);
 }
 #else
-typedef VOID(*handover_f)(VOID *image, EFI_SYSTEM_TABLE *table, struct SetupHeader *setup) __attribute__((regparm(0)));
-static VOID linux_efi_handover(EFI_HANDLE image, struct SetupHeader *setup) {
+typedef VOID(*handover_f)(VOID *image, EFI_SYSTEM_TABLE *table, struct boot_params *params) __attribute__((regparm(0)));
+static VOID linux_efi_handover(EFI_HANDLE image, struct boot_params *params) {
         handover_f handover;
 
-        handover = (handover_f)((UINTN)setup->code32_start + setup->handover_offset);
-        handover(image, ST, setup);
+        handover = (handover_f)((UINTN)params->hdr.code32_start + params->hdr.handover_offset);
+        handover(image, ST, params);
 }
 #endif
 
@@ -73,29 +29,31 @@ EFI_STATUS linux_exec(EFI_HANDLE *image,
                       CHAR8 *cmdline, UINTN cmdline_len,
                       UINTN linux_addr,
                       UINTN initrd_addr, UINTN initrd_size) {
-        struct SetupHeader *image_setup;
-        struct SetupHeader *boot_setup;
+        struct boot_params *image_params;
+        struct boot_params *boot_params;
+        UINT8 setup_sectors;
         EFI_PHYSICAL_ADDRESS addr;
         EFI_STATUS err;
 
-        image_setup = (struct SetupHeader *)(linux_addr);
-        if (image_setup->signature != 0xAA55 || image_setup->header != SETUP_MAGIC)
-                return EFI_LOAD_ERROR;
+        image_params = (struct boot_params *) linux_addr;
 
-        if (image_setup->version < 0x20b || !image_setup->relocatable_kernel)
+        if (image_params->hdr.boot_flag != 0xAA55 ||
+            image_params->hdr.header != SETUP_MAGIC ||
+            image_params->hdr.version < 0x20b ||
+            !image_params->hdr.relocatable_kernel)
                 return EFI_LOAD_ERROR;
 
-        addr = 0x3fffffff;
+        boot_params = (struct boot_params *) 0xFFFFFFFF;
         err = uefi_call_wrapper(BS->AllocatePages, 4, AllocateMaxAddress, EfiLoaderData,
-                                EFI_SIZE_TO_PAGES(0x4000), &addr);
+                                EFI_SIZE_TO_PAGES(0x4000), (UINTN *) &boot_params);
         if (EFI_ERROR(err))
                 return err;
-        boot_setup = (struct SetupHeader *)(UINTN)addr;
-        ZeroMem(boot_setup, 0x4000);
-        CopyMem(boot_setup, image_setup, sizeof(struct SetupHeader));
-        boot_setup->loader_id = 0xff;
 
-        boot_setup->code32_start = (UINT32)linux_addr + (image_setup->setup_secs+1) * 512;
+        ZeroMem(boot_params, 0x4000);
+        CopyMem(&boot_params->hdr, &image_params->hdr, sizeof(struct setup_header));
+        boot_params->hdr.type_of_loader = 0xff;
+        setup_sectors = image_params->hdr.setup_sects > 0 ? image_params->hdr.setup_sects : 4;
+        boot_params->hdr.code32_start = (UINT32)linux_addr + (setup_sectors + 1) * 512;
 
         if (cmdline) {
                 addr = 0xA0000;
@@ -105,12 +63,12 @@ EFI_STATUS linux_exec(EFI_HANDLE *image,
                         return err;
                 CopyMem((VOID *)(UINTN)addr, cmdline, cmdline_len);
                 ((CHAR8 *)(UINTN)addr)[cmdline_len] = 0;
-                boot_setup->cmd_line_ptr = (UINT32)addr;
+                boot_params->hdr.cmd_line_ptr = (UINT32)addr;
         }
 
-        boot_setup->ramdisk_start = (UINT32)initrd_addr;
-        boot_setup->ramdisk_len = (UINT32)initrd_size;
+        boot_params->hdr.ramdisk_image = (UINT32)initrd_addr;
+        boot_params->hdr.ramdisk_size = (UINT32)initrd_size;
 
-        linux_efi_handover(image, boot_setup);
+        linux_efi_handover(image, boot_params);
         return EFI_LOAD_ERROR;
 }
diff --git a/src/boot/efi/linux.h b/src/boot/efi/linux.h
index 4cae99773b..ec655ce647 100644
--- a/src/boot/efi/linux.h
+++ b/src/boot/efi/linux.h
@@ -1,6 +1,86 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 #pragma once
 
+#define SETUP_MAGIC             0x53726448      /* "HdrS" */
+
+struct setup_header {
+        UINT8  setup_sects;
+        UINT16 root_flags;
+        UINT32 syssize;
+        UINT16 ram_size;
+        UINT16 vid_mode;
+        UINT16 root_dev;
+        UINT16 boot_flag;
+        UINT16 jump;
+        UINT32 header;
+        UINT16 version;
+        UINT32 realmode_swtch;
+        UINT16 start_sys_seg;
+        UINT16 kernel_version;
+        UINT8  type_of_loader;
+        UINT8  loadflags;
+        UINT16 setup_move_size;
+        UINT32 code32_start;
+        UINT32 ramdisk_image;
+        UINT32 ramdisk_size;
+        UINT32 bootsect_kludge;
+        UINT16 heap_end_ptr;
+        UINT8  ext_loader_ver;
+        UINT8  ext_loader_type;
+        UINT32 cmd_line_ptr;
+        UINT32 initrd_addr_max;
+        UINT32 kernel_alignment;
+        UINT8  relocatable_kernel;
+        UINT8  min_alignment;
+        UINT16 xloadflags;
+        UINT32 cmdline_size;
+        UINT32 hardware_subarch;
+        UINT64 hardware_subarch_data;
+        UINT32 payload_offset;
+        UINT32 payload_length;
+        UINT64 setup_data;
+        UINT64 pref_address;
+        UINT32 init_size;
+        UINT32 handover_offset;
+} __attribute__((packed));
+
+/* adapted from linux' bootparam.h */
+struct boot_params {
+        UINT8  screen_info[64];         // was: struct screen_info
+        UINT8  apm_bios_info[20];       // was: struct apm_bios_info
+        UINT8  _pad2[4];
+        UINT64 tboot_addr;
+        UINT8  ist_info[16];            // was: struct ist_info
+        UINT8  _pad3[16];
+        UINT8  hd0_info[16];
+        UINT8  hd1_info[16];
+        UINT8  sys_desc_table[16];      // was: struct sys_desc_table
+        UINT8  olpc_ofw_header[16];     // was: struct olpc_ofw_header
+        UINT32 ext_ramdisk_image;
+        UINT32 ext_ramdisk_size;
+        UINT32 ext_cmd_line_ptr;
+        UINT8  _pad4[116];
+        UINT8  edid_info[128];          // was: struct edid_info
+        UINT8  efi_info[32];            // was: struct efi_info
+        UINT32 alt_mem_k;
+        UINT32 scratch;
+        UINT8  e820_entries;
+        UINT8  eddbuf_entries;
+        UINT8  edd_mbr_sig_buf_entries;
+        UINT8  kbd_status;
+        UINT8  secure_boot;
+        UINT8  _pad5[2];
+        UINT8  sentinel;
+        UINT8  _pad6[1];
+        struct setup_header hdr;
+        UINT8  _pad7[0x290-0x1f1-sizeof(struct setup_header)];
+        UINT32 edd_mbr_sig_buffer[16];  // was: edd_mbr_sig_buffer[EDD_MBR_SIG_MAX]
+        UINT8  e820_table[20*128];      // was: struct boot_e820_entry e820_table[E820_MAX_ENTRIES_ZEROPAGE]
+        UINT8  _pad8[48];
+        UINT8  eddbuf[6*82];            // was: struct edd_info eddbuf[EDDMAXNR]
+        UINT8  _pad9[276];
+} __attribute__((packed));
+
 EFI_STATUS linux_exec(EFI_HANDLE *image,
                       CHAR8 *cmdline, UINTN cmdline_size,
                       UINTN linux_addr,