[PATCH v2] x86, boot: Allow 64bit EFI kernel to be loaded above 4G
From: Yinghai Lu
Date: Sun Feb 22 2015 - 22:45:17 EST
Now could use kexec to place kernel/boot_params/cmd_line/initrd
above 4G, but that is with legacy interface with startup_64 directly.
This patch will allow 64bit EFI kernel to be loaded above 4G
and use EFI HANDOVER PROTOCOL to start the kernel.
Current 32bit code32_start is used for passing around load address,
so it will overflow when kernel is loaded abover 4G.
The patch mainly add ext_code32_start to take load address high 32bits.
After this patch, could use patched grub2-x86_64.efi to place
kernel/boot_params/cmd_line/initrd all above 4G and execute the kernel
above 4G.
bootlog like:
kernel: done [ linux 9.25MiB 100% 6.66MiB/s ]
params: [1618fc000,1618fffff]
cmdline: [1618fb000,1618fb7fe]
kernel: [15e000000,161385fff]
initrd: [15bcbe000,15dffffbb]
initrd: 1 file done [ initrd.img 35.26MiB 100% 11.93MiB/s ]
early console in decompress_kernel
decompress_kernel:
input: [0x15fd0b3b4-0x16063c803], output: 0x15e000000, heap: [0x160645b00-0x16064daff]
Decompressing Linux... xz... Parsing ELF... done.
Booting the kernel.
[ 0.000000] bootconsole [uart0] enabled
[ 0.000000] real_mode_data : phys 00000001618fc000
[ 0.000000] real_mode_data : virt ffff8801618fc000
[ 0.000000] Kernel Layout:
[ 0.000000] .text: [0x15e000000-0x15f08f72c]
[ 0.000000] .rodata: [0x15f200000-0x15fa44fff]
[ 0.000000] .data: [0x15fc00000-0x15fe545ff]
[ 0.000000] .init: [0x15fe56000-0x16021afff]
[ 0.000000] .bss: [0x160229000-0x16135ffff]
[ 0.000000] .brk: [0x161360000-0x161385fff]
[ 0.000000] memblock_reserve: [0x0000000009f000-0x000000000fffff] flags 0x0 * BIOS reserved
...
[ 0.000000] memblock_reserve: [0x0000015e000000-0x0000016135ffff] flags 0x0 TEXT DATA BSS
[ 0.000000] memblock_reserve: [0x0000015bcbe000-0x0000015dffffff] flags 0x0 RAMDISK
-v2: add cast to avoid warning with 32bit, also update description for
ext_code32_start in boot.txt
Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
---
Documentation/x86/boot.txt | 19 +++++++++++++++++++
arch/x86/boot/compressed/eboot.c | 15 ++++++++++-----
arch/x86/boot/compressed/head_64.S | 7 ++++++-
arch/x86/boot/header.S | 3 ++-
arch/x86/include/uapi/asm/bootparam.h | 1 +
arch/x86/kernel/asm-offsets.c | 1 +
6 files changed, 39 insertions(+), 7 deletions(-)
Index: linux-2.6/arch/x86/include/uapi/asm/bootparam.h
===================================================================
--- linux-2.6.orig/arch/x86/include/uapi/asm/bootparam.h
+++ linux-2.6/arch/x86/include/uapi/asm/bootparam.h
@@ -84,6 +84,7 @@ struct setup_header {
__u64 pref_address;
__u32 init_size;
__u32 handover_offset;
+ __u32 ext_code32_start;
} __attribute__((packed));
struct sys_desc_table {
Index: linux-2.6/arch/x86/kernel/asm-offsets.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/asm-offsets.c
+++ linux-2.6/arch/x86/kernel/asm-offsets.c
@@ -68,6 +68,7 @@ void common(void) {
OFFSET(BP_kernel_alignment, boot_params, hdr.kernel_alignment);
OFFSET(BP_pref_address, boot_params, hdr.pref_address);
OFFSET(BP_code32_start, boot_params, hdr.code32_start);
+ OFFSET(BP_ext_code32_start, boot_params, hdr.ext_code32_start);
BLANK();
DEFINE(PTREGS_SIZE, sizeof(struct pt_regs));
Index: linux-2.6/arch/x86/boot/compressed/head_64.S
===================================================================
--- linux-2.6.orig/arch/x86/boot/compressed/head_64.S
+++ linux-2.6/arch/x86/boot/compressed/head_64.S
@@ -264,6 +264,8 @@ ENTRY(efi_pe_entry)
mov %rax, %rsi
leaq startup_32(%rip), %rax
movl %eax, BP_code32_start(%rsi)
+ shr $32, %rax
+ movl %eax, BP_ext_code32_start(%rsi)
jmp 2f /* Skip the relocation */
handover_entry:
@@ -287,7 +289,10 @@ fail:
hlt
jmp fail
2:
- movl BP_code32_start(%esi), %eax
+ movl BP_code32_start(%rsi), %eax
+ movl BP_ext_code32_start(%rsi), %ebx
+ shl $32, %rbx
+ orq %rbx, %rax
leaq preferred_addr(%rax), %rax
jmp *%rax
Index: linux-2.6/arch/x86/boot/compressed/eboot.c
===================================================================
--- linux-2.6.orig/arch/x86/boot/compressed/eboot.c
+++ linux-2.6/arch/x86/boot/compressed/eboot.c
@@ -1388,6 +1388,7 @@ struct boot_params *efi_main(struct efi_
void *handle;
efi_system_table_t *_table;
bool is64;
+ unsigned long loaded_addr;
efi_early = c;
@@ -1429,9 +1430,12 @@ struct boot_params *efi_main(struct efi_
* If the kernel isn't already loaded at the preferred load
* address, relocate it.
*/
- if (hdr->pref_address != hdr->code32_start) {
- unsigned long bzimage_addr = hdr->code32_start;
- status = efi_relocate_kernel(sys_table, &bzimage_addr,
+ loaded_addr = hdr->code32_start;
+ loaded_addr |= (unsigned long)((u64)hdr->ext_code32_start << 32);
+ if (hdr->pref_address != loaded_addr) {
+ unsigned long loaded_addr_orig = loaded_addr;
+
+ status = efi_relocate_kernel(sys_table, &loaded_addr,
hdr->init_size, hdr->init_size,
hdr->pref_address,
hdr->kernel_alignment);
@@ -1440,8 +1444,9 @@ struct boot_params *efi_main(struct efi_
goto fail;
}
- hdr->pref_address = hdr->code32_start;
- hdr->code32_start = bzimage_addr;
+ hdr->pref_address = loaded_addr_orig;
+ hdr->code32_start = loaded_addr & 0xffffffff;
+ hdr->ext_code32_start = (unsigned long)((u64)loaded_addr >> 32);
}
status = exit_boot(boot_params, handle, is64);
Index: linux-2.6/arch/x86/boot/header.S
===================================================================
--- linux-2.6.orig/arch/x86/boot/header.S
+++ linux-2.6/arch/x86/boot/header.S
@@ -301,7 +301,7 @@ _start:
# Part 2 of the header, from the old setup.S
.ascii "HdrS" # header signature
- .word 0x020d # header version number (>= 0x0105)
+ .word 0x020e # header version number (>= 0x0105)
# or else old loadlin-1.5 will fail)
.globl realmode_swtch
realmode_swtch: .word 0, 0 # default_switch, SETUPSEG
@@ -449,6 +449,7 @@ pref_address: .quad LOAD_PHYSICAL_ADDR
#endif
init_size: .long INIT_SIZE # kernel initialization size
handover_offset: .long 0 # Filled in by build.c
+ext_code32_start: .long 0 # werid one!
# End of setup header #####################################################
Index: linux-2.6/Documentation/x86/boot.txt
===================================================================
--- linux-2.6.orig/Documentation/x86/boot.txt
+++ linux-2.6/Documentation/x86/boot.txt
@@ -61,6 +61,9 @@ Protocol 2.12: (Kernel 3.8) Added the xl
to struct boot_params for loading bzImage and ramdisk
above 4G in 64bit.
+Protocol 2.14: (Kernel 3.20) Added the ext_code32_start to support 64bit
+ EFI kernel to be loaded above 4G.
+
**** MEMORY LAYOUT
The traditional memory map for the kernel loader, used for Image or
@@ -197,6 +200,7 @@ Offset Proto Name Meaning
0258/8 2.10+ pref_address Preferred loading address
0260/4 2.10+ init_size Linear memory required during initialization
0264/4 2.11+ handover_offset Offset of handover entry point
+0268/4 2.14+ ext_code32_start Extended part for code32_start
(1) For backwards compatibility, if the setup_sects field contains 0, the
real value is 4.
@@ -738,6 +742,14 @@ Offset/size: 0x264/4
See EFI HANDOVER PROTOCOL below for more details.
+Field name: ext_code32_start
+Type: modify (optional, reloc)
+Offset/size: 0x268/4
+Protocol: 2.14+
+
+ This field is the upper 32bits of load address when EFI 64bit kernel
+ is loaded above 4G. And it is used with code32_start to compare to
+ pref_address to decide if kernel need to be relocated further.
**** THE IMAGE CHECKSUM
@@ -1122,4 +1134,11 @@ The boot loader *must* fill out the foll
o hdr.ramdisk_image (if applicable)
o hdr.ramdisk_size (if applicable)
+for 64bit, when loading above 4G, *must* fill out the following fields,
+
+ o hdr.ext_code32_start
+ o ext_cmd_line_ptr
+ o ext_ramdisk_image (if applicable)
+ o ext_ramdisk_size (if applicable)
+
All other fields should be zero.
--
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