The kexec_buf structure was previously declared without initialization.
commit bf454ec31a ("kexec_file: allow to place kexec_buf randomly")
added a field that is always read but not consistently populated by all
architectures. This un-initialized field will contain garbage.
This is also triggering a UBSAN warning when the uninitialized data is
accessed:
------------[ cut here ]------------
UBSAN: invalid-load in ./include/linux/kexec.h:210:10
load of value 252 is not a valid value for type '_Bool'
Zero-initializing kexec_buf at declaration ensures all fields are
cleanly set, preventing future instances of uninitialized memory being
used.
Fixes: bf454ec31a ("kexec_file: allow to place kexec_buf randomly")
Link: https://lore.kernel.org/r/20250827-kbuf_all-v1-2-1df9882bb01a@debian.org
Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This patch creates kexec_elf_ops to load ELF binary file for
kexec_file_load() syscall.
However, for `kbuf->memsz` and `kbuf->buf_min`, special handling is
required, and the generic `kexec_elf_load()` cannot be used directly.
$ readelf -l vmlinux
...
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000010000 0x9000000000200000 0x9000000000200000
0x0000000002747a00 0x000000000287a0d8 RWE 0x10000
NOTE 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 R 0x8
phdr->p_paddr should have been a physical address, but it is a virtual
address on the current LoongArch. This will cause kexec_file to fail
when loading the kernel and need to be converted to a physical address.
From the above MemSiz, it can be seen that 0x287a0d8 isn't page aligned.
Although kexec_add_buffer() will perform PAGE_SIZE alignment on kbuf->
memsz, there is still a stampeding in the loaded kernel space and initrd
space. The initrd resolution failed when starting the second kernel.
It can be known from the link script vmlinux.lds.S that,
BSS_SECTION(0, SZ_64K, 8)
. = ALIGN(PECOFF_SEGMENT_ALIGN);
It needs to be aligned according to SZ_64K, so that after alignment, its
size is consistent with _kernel_asize.
The basic usage (vmlinux):
1) Load second kernel image:
# kexec -s -l vmlinux --initrd=initrd.img --reuse-cmdline
2) Startup second kernel:
# kexec -e
Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
