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    SubjectRe: [PATCH] x86, boot: Allow 64bit EFI kernel to be loaded above 4G
    Hi,

    Thanks, it will be useful for possible efi rebooting to kdump reserved memory.

    On 02/03/15 at 06:03pm, Yinghai Lu wrote:
    > 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 code32_start is used for passing around loading address,
    > so it will overflow when kernel is loaded abover 4G.
    >
    > The patch mainly add ext_code32_start to take address high 32bit.
    >
    > 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.

    Can you share the grub2 patch for testing?

    >
    > bootlog like:
    >
    > params: [1618fc000,1618fffff]
    > cmdline: [1618fb000,1618fb7fe]
    > kernel: [15e000000,161385fff]
    > kernel: done [ linux 9.25MiB 100% 6.66MiB/s ]
    > 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
    >
    >
    > Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    >
    > ---
    > Documentation/x86/boot.txt | 18 ++++++++++++++++++
    > 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, 38 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
    > @@ -83,6 +83,7 @@ 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
    > @@ -263,6 +263,8 @@ 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:
    > @@ -286,7 +288,10 @@ 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
    > @@ -1389,6 +1389,7 @@ struct boot_params *efi_main(struct efi_
    > void *handle;
    > efi_system_table_t *_table;
    > bool is64;
    > + unsigned long loaded_addr;
    >
    > efi_early = c;
    >
    > @@ -1430,9 +1431,12 @@ 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)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);
    > @@ -1441,8 +1445,9 @@ 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 = 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 EFI64
    > + 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 +742,13 @@ 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+
    > +
    > + The address is used with code32_start to compare pref_address
    > + to support EFI 64bit kernel get loaded above 4G.
    >
    > **** THE IMAGE CHECKSUM
    >
    > @@ -1122,4 +1133,11 @@ 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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