From: Gerald Schaefer gerald.schaefer@de.ibm.com
commit a9f2f6865d784477e1c7b59269d3a384abafd9ca upstream.
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: stable@vger.kernel.org # v5.2+ Signed-off-by: Gerald Schaefer gerald.schaefer@de.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/s390/boot/startup.c | 5 +++++ arch/s390/kernel/machine_kexec.c | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-)
--- a/arch/s390/boot/startup.c +++ b/arch/s390/boot/startup.c @@ -164,6 +164,11 @@ 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); --- a/arch/s390/kernel/machine_kexec.c +++ b/arch/s390/kernel/machine_kexec.c @@ -254,10 +254,10 @@ void arch_crash_save_vmcoreinfo(void) VMCOREINFO_SYMBOL(lowcore_ptr); VMCOREINFO_SYMBOL(high_memory); VMCOREINFO_LENGTH(lowcore_ptr, NR_CPUS); - mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note()); vmcoreinfo_append_str("SDMA=%lx\n", __sdma); vmcoreinfo_append_str("EDMA=%lx\n", __edma); vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset()); + mem_assign_absolute(S390_lowcore.vmcore_info, paddr_vmcoreinfo_note()); }
void machine_shutdown(void)