Succeed: UEFI(DT) ------> Kernel+U-root (Image) ---kexec---> Ubuntu
Fail: UEFI(ACPI) ------> Kernel+U-root (Image) ---x---> Ubuntu
Succeed: UEFI(ACPI) --grub--> Ubuntu --kexec--> Kernel+U-root (Image) --kexec--> Ubuntu
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Run Ubuntu Cloud Image on qemu-kvm on ARM Machine, for fast compiling.
Get linux kernel source code:
sudo apt-get install linux-source
sudo apt-get install libncurses5-dev
Install kernel:
mkdir kernel
cp /usr/src/linux-source-5.4.0.tar.bz2 ./kernel
cd kernel
tar xf linux-source-5.4.0.tar.bz2
cd linux-source-5.4.0
cp /boot/config-5.4.0-42-generic .config
make -j $(npro)
make modules
make modules_install
make install- Upload the vmlinux and vmlinuz file to personal server, then download the files to host machine(x86):
On ARM Machine:
scp vmlinux bruce@xxx.xxx.xx.xxx:/home/Ubuntu_Files
cd /boot
scp vmlinuz-5.4.44 initrd.img-5.4.44 bruce@xxx.xxx.xx.xxx:/home/Ubuntu_Files
On x86 Machine:
cd /disk/system/ARM
mkdir Ubuntu_Files
scp bruce@xxx.xxx.xx.xxx:/home/Ubuntu_Files/* ./Ubuntu_Files/-
Create a virtual disk to store the vmlinuz and initrd:
cd /disk/system/ARM qemu-img create -f raw disk.img 1G mkdir disk_file sudo mkfs.vfat -F 32 disk.img sudo mount -o loop disk.img disk_file sudo cp Ubuntu_Files/* ../disk_file/ sudo umount disk_file
- Install latest GDB-AARCH64
cd /disk/tools
wget https://ftp.gnu.org/gnu/gdb/gdb-9.2.tar.gz
cd gdb-9.2
mkdir build
cd build
../configure --target=aarch64-linux-gnu --program-prefix=aarch64-linux-gnu- --prefix=/usr/bin
make
make install
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qemu support for gdb:
sudo qemu-system-aarch64 -s \ # it will set a 1234 port for gdb to connect -machine virt -cpu cortex-a57 \ -nographic \ -m 6G -smp 7 \ -bios QEMU_EFI.fd \ # UEFI with ACPI -kernel Image_5.4 \ # Kernel with U-root -device virtio-net-pci,netdev=net0,romfile="" \ -netdev type=user,id=net0 \ -drive file=disk.img,format=raw # Disk image Stores vmlinuz and initrd -
GDB connect and set Breakpoint
cd /disk/system/kernel/linux-source-5.4.0 /disk/tools/gdb-9.2/build/gdb/gdb ./vmlinux_Ubuntu gdb: target remote localhost:1234 b start_kernel ......
Cannot find available physical address in memblock
start_kernel
setup_arch
(arch/arm64/mm/mmu.c:)
paging_init
map_kernel 701
map_kernel_segment 656
__create_pgd_mapping 550
alloc_init_pud 359
pud_phys = pgtable_alloc(PUD_SHIFT); 297
early_pgtable_alloc 95 memblock_phys_alloc
memblock_phys_alloc_range
memblock_alloc_range_nid
found = memblock_find_in_range_node(mm/memblock.c:1373)
# cannot find available physical address in memblock
panic("Failed to allocate page table page\n");
It seems that memblock.memory.total_size is changed after efi_init();
Besides, if UEFI using DT to config kernel, memblock will be initialized in setup_machine_fdt().
In setup_arch:
291 setup_machine_fdt(__fdt_pointer);
(gdb) p memblock
$2 = { bottom_up = false,
current_limit = 18446744073709551615,
memory = {cnt = 1,
max = 128,
total_size = 0,
regions = 0xffff800011dd89c8 <memblock_memory_init_regions>,
name = 0xffff8000112d96f0 "memory"},
reserved = {cnt = 1,
max = 385,
total_size = 0,
regions = 0xffff800011dd95d0 <memblock_reserved_init_regions>,
name = 0xffff8000112017d0 "reserved"}}
314 efi_init();
(gdb) p memblock
$8 = { bottom_up = false,
current_limit = 18446744073709551615,
memory = {cnt = 1,
max = 128,
total_size = 0,
regions = 0xffff800011dd89c8 <memblock_memory_init_regions>,
name = 0xffff8000112d96f0 "memory"},
reserved = {cnt = 1,
max = 385,
total_size = 513,
regions = 0xffff800011dd95d0 <memblock_reserved_init_regions>,
name = 0xffff8000112017d0 "reserved"}}
315 arm64_memblock_init();
(gdb) p memblock
$9 = { bottom_up = false,
current_limit = 18446744073709551615,
memory = { cnt = 7,
max = 128,
total_size = 6442450944,
regions = 0xffff800011dd89c8 <memblock_memory_init_regions>,
name = 0xffff8000112d96f0 "memory"},
reserved = {cnt = 6,
max = 385,
total_size = 530033,
regions = 0xffff800011dd95d0 <memblock_reserved_init_regions>,
name = 0xffff8000112017d0 "reserved"}}
setup_arch
efi_init
if (!efi_get_fdt_params(¶ms)) # set params from fdt
return; # if cannot get fdt, return
data = params # set data by params
efi_memmap_init_early(&data)
__efi_memmap_init(data, false)
efi.memmap = map; #set efi.memmap by data
reserve_regions()
for_each_efi_memory_desc (md) == for_each_efi_memory_desc_in_map(&efi.memmap, md)
paddr = md->phys_addr;
npages = md->num_pages;
size = npages << PAGE_SHIFT;
early_init_dt_add_memory_arch(paddr, size);
memblock_add(base, size); # set the memblock by efi.memmap
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if (!efi_get_fdt_params(¶ms)) return; # program returned hereExplore
efi_get_fdt_params: info.miss = "Secure Boot Enabled", ret =0, so this func will return 0.
int __init efi_get_fdt_params(struct efi_fdt_params *params) { struct param_info info; int ret; pr_info("Getting EFI parameters from FDT:\n"); info.found = 0; info.params = params; ret = of_scan_flat_dt(fdt_find_uefi_params, &info); /* * (gdb) p info * $5 = {found = 5, params = 0xffff800011b03ec8, * missing = 0xffff8000115801c8 <fdt_params+360> "Secure Boot Enabled"} * * (gdb) p info * $6 ret = 0 */ if (!info.found) pr_info("UEFI not found.\n"); else if (!ret) pr_err("Can't find '%s' in device tree!\n", info.missing); return ret; }Explore
fdt_find_uefi_params: Get uname from fdt, then compare is with
dt_params[i].name. When the uname cannot be found in
dt_params[i],info->missingwill be set.static int __init fdt_find_uefi_params(unsigned long node, const char *uname, int depth, void *data) { struct param_info *info = data; int i; for (i = 0; i < ARRAY_SIZE(dt_params); i++) { const char *subnode = dt_params[i].subnode; if (depth != 1 || strcmp(uname, dt_params[i].uname) != 0) { info->missing = dt_params[i].params[0].name; continue; } /* * when cannot find the name in dt_params[i], * info->missing will be set. */ if (subnode) { int err = of_get_flat_dt_subnode_by_name(node, subnode); if (err < 0) return 0; node = err; } return __find_uefi_params(node, info, dt_params[i].params); } return 0; }Check
dt_params:static __initdata struct params fdt_params[] = { UEFI_PARAM("System Table", "linux,uefi-system-table", system_table), UEFI_PARAM("MemMap Address", "linux,uefi-mmap-start", mmap), UEFI_PARAM("MemMap Size", "linux,uefi-mmap-size", mmap_size), UEFI_PARAM("MemMap Desc. Size", "linux,uefi-mmap-desc-size", desc_size), UEFI_PARAM("MemMap Desc. Version", "linux,uefi-mmap-desc-ver", desc_ver), UEFI_PARAM("Secure Boot Enabled", "linux,uefi-secure-boot", secure_boot) }; static __initdata struct params xen_fdt_params[] = { UEFI_PARAM("System Table", "xen,uefi-system-table", system_table), UEFI_PARAM("MemMap Address", "xen,uefi-mmap-start", mmap), UEFI_PARAM("MemMap Size", "xen,uefi-mmap-size", mmap_size), UEFI_PARAM("MemMap Desc. Size", "xen,uefi-mmap-desc-size", desc_size), UEFI_PARAM("MemMap Desc. Version", "xen,uefi-mmap-desc-ver", desc_ver) }; static __initdata struct { const char *uname; const char *subnode; struct params *params; } dt_params[] = { { "hypervisor", "uefi", xen_fdt_params }, { "chosen", NULL, fdt_params }, };
When UEFI using ACPI to config kernel, the kernel will generate an empty DT which contains some EFI map messages, commandline, physical address for linux etc. However, when Ubuntu is booted by grub, the fdt it generated contains a node called "uefi-secure-boot", which cannot be generated by the kernel built by my own. Thus, when my linux with u-root is booting Ubuntu by kexec, Ubuntu cannot find the "uefi-secure-boot" node from fdt, and consequently goes wrong.
Comment the line blow in kernel code and Ubuntu will not try to find this node.
UEFI_PARAM("Secure Boot Enabled", "linux,uefi-secure-boot", secure_boot)
True solution should be:
Modifying the source code of Linux kernel built on my own, to generate an additional "uefi-secure-boot" node.