Ciro Santilli @cirosantilli 37

./run --gdb-wait

./run-gdb start_kernel

Breakpoint 1, start_kernel () at /root/lkmc/submodules/linux/init/main.c:837
837     {
loading vmlinux
(gdb) n
841             set_task_stack_end_magic(&init_task);
(gdb) l
836     asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
837     {
838             char *command_line;
839             char *after_dashes;
840
841             set_task_stack_end_magic(&init_task);
842             smp_setup_processor_id();
843             debug_objects_early_init();
844
845             cgroup_init_early();
(gdb) p &init_task
$1 = (struct task_struct *) 0xffffffff82012840 <init_task>
(gdb) bt
#0  start_kernel () at /root/lkmc/submodules/linux/init/main.c:841
#1  0xffffffff8215145c in x86_64_start_reservations (real_mode_data=<optimized out>) at /root/lkmc/submodules/linux/arch/x86/kernel/head64.c:490
#2  0xffffffff821514e3 in x86_64_start_kernel (real_mode_data=0x138d0 <bts_ctx+2256> <error: Cannot access memory at address 0x138d0>) at /root/lkmc/submodules/linux/arch/x86/kernel/head64.c:471
#3  0xffffffff810000e6 in secondary_startup_64 () at /root/lkmc/submodules/linux/arch/x86/kernel/head_64.S:243
#4  0x0000000000000000 in ?? ()
(gdb) up
#1  0xffffffff8215145c in x86_64_start_reservations (real_mode_data=<optimized out>) at /root/lkmc/submodules/linux/arch/x86/kernel/head64.c:490
490             start_kernel();
(gdb) l
485                     break;
486             default:
487                     break;
488             }
489
490             start_kernel();
491     }

submodules/binutils-gdb/
submodules/buildroot/
submodules/gcc/
submodules/glibc/
submodules/linux/
submodules/qemu/

git clone https://github.com/cirosantilli/linux-kernel-module-cheat
cd linux-kernel-module-cheat
sudo apt install docker
python3 -m venv .venv
. .venv/bin/activate
./setup
./run-docker create
./run-docker sh

./build --download-dependencies qemu-buildroot

./run

<6>[    1.383114] NET: Registered protocol family 17
<6>[    1.383682] 9pnet: Installing 9P2000 support
<6>[    1.385473] IPI shorthand broadcast: enabled
<6>[    1.385701] sched_clock: Marking stable (1355697980, 27047205)->(1385555667, -2810482)
<6>[    1.387744] ALSA device list:
<6>[    1.387843]   No soundcards found.
<6>[    1.535981] ata2.00: ATAPI: QEMU DVD-ROM, 2.5+, max UDMA/100
<5>[    1.543470] scsi 1:0:0:0: CD-ROM            QEMU     QEMU DVD-ROM     2.5+ PQ: 0 ANSI: 5
<6>[    1.548952] EXT4-fs (vda): mounting ext2 file system using the ext4 subsystem
<6>[    1.555909] EXT4-fs (vda): mounted filesystem without journal. Opts: (null)
<6>[    1.556145] VFS: Mounted root (ext2 filesystem) on device 254:0.
<6>[    1.557451] devtmpfs: mounted
<6>[    1.605639] Freeing unused kernel image (initmem) memory: 1248K
<6>[    1.605875] Write protecting the kernel read-only data: 16384k
<6>[    1.607977] Freeing unused kernel image (text/rodata gap) memory: 2044K
<6>[    1.610190] Freeing unused kernel image (rodata/data gap) memory: 1012K
<6>[    1.610495] Run /sbin/init as init process
<6>[    1.683311] tsc: Refined TSC clocksource calibration: 3293.671 MHz
<6>[    1.683618] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x2f79f177aae, max_idle_ns: 440795226653 ns
<6>[    1.683849] clocksource: Switched to clocksource tsc
<3>[    1.694241] 9pnet_virtio: no channels available for device host_data
mount: mounting host_data on /mnt/9p/data failed: No such file or directory
qemu-system-x86_64: warning: 9p: degraded performance: a reasonable high msize should be chosen on client/guest side (chosen msize is <= 8192). See https://wiki.qemu.org/Documentation/9pset.
<3>[    1.712287] overlayfs: overlapping upperdir path
mount: mounting overlay on /mnt/overlay failed: Too many levels of symbolic links
hello S98
hello .profile
/lkmc
root@buildroot# pwd
/lkmc
/lkmc
root@buildroot#