For kexec_file loading, if kexec_buf.top_down is 'true', the memory which is used to load kernel/initrd/purgatory is supposed to be allocated from top to down. This is what we have been doing all along in the old kexec loading interface and the kexec loading is still default setting in some distributions. However, the current kexec_file loading interface doesn't do likt this. The function arch_kexec_walk_mem() it calls ignores checking kexec_buf.top_down, but calls walk_system_ram_res() directly to go through all resources of System RAM from bottom to up, to try to find memory region which can contain the specific kexec buffer, then call locate_mem_hole_callback() to allocate memory in that found memory region from top to down. This brings confusion especially when KASLR is widely supported , users have to make clear why kexec/kdump kernel loading position is different between these two interfaces in order to exclude unnecessary noises. Hence these two interfaces need be unified on behaviour. Here add checking if kexec_buf.top_down is 'true' in arch_kexec_walk_mem(), if yes, call the newly added walk_system_ram_res_rev() to find memory region from top to down to load kernel. Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> Cc: Dave Young <dyoung@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Yinghai Lu <yinghai@xxxxxxxxxx> Cc: kexec@xxxxxxxxxxxxxxxxxxx --- kernel/kexec_file.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index c6a3b6851372..75226c1d08ce 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -518,6 +518,8 @@ int __weak arch_kexec_walk_mem(struct kexec_buf *kbuf, IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY, crashk_res.start, crashk_res.end, kbuf, func); + else if (kbuf->top_down) + return walk_system_ram_res_rev(0, ULONG_MAX, kbuf, func); else return walk_system_ram_res(0, ULONG_MAX, kbuf, func); } -- 2.13.6
