From a9f2f6865d784477e1c7b59269d3a384abafd9ca Mon Sep 17 00:00:00 2001 From: Gerald Schaefer Date: Tue, 19 Nov 2019 12:30:53 +0100 Subject: s390/kaslr: store KASLR offset for early dumps The KASLR offset is added to vmcoreinfo in arch_crash_save_vmcoreinfo(), so that it can be found by crash when processing kernel dumps. However, arch_crash_save_vmcoreinfo() is called during a subsys_initcall, so if the kernel crashes before that, we have no vmcoreinfo and no KASLR offset. Fix this by storing the KASLR offset in the lowcore, where the vmcore_info pointer will be stored, and where it can be found by crash. In order to make it distinguishable from a real vmcore_info pointer, mark it as uneven (KASLR offset itself is aligned to THREAD_SIZE). When arch_crash_save_vmcoreinfo() stores the real vmcore_info pointer in the lowcore, it overwrites the KASLR offset. At that point, the KASLR offset is not yet added to vmcoreinfo, so we also need to move the mem_assign_absolute() behind the vmcoreinfo_append_str(). Fixes: b2d24b97b2a9 ("s390/kernel: add support for kernel address space layout randomization (KASLR)") Cc: # v5.2+ Signed-off-by: Gerald Schaefer Signed-off-by: Vasily Gorbik --- arch/s390/boot/startup.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'arch/s390/boot') diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c index fbd341ea03b8..3b3a11f95269 100644 --- a/arch/s390/boot/startup.c +++ b/arch/s390/boot/startup.c @@ -170,6 +170,11 @@ void startup_kernel(void) handle_relocs(__kaslr_offset); if (__kaslr_offset) { + /* + * Save KASLR offset for early dumps, before vmcore_info is set. + * Mark as uneven to distinguish from real vmcore_info pointer. + */ + S390_lowcore.vmcore_info = __kaslr_offset | 0x1UL; /* Clear non-relocated kernel */ if (IS_ENABLED(CONFIG_KERNEL_UNCOMPRESSED)) memset(img, 0, vmlinux.image_size); -- cgit v1.2.3