On 10/11/2017 09:00 AM, Konstantin Khlebnikov wrote: > On 11.10.2017 01:25, Andrew Morton wrote: >> On Fri, 06 Oct 2017 14:32:34 +0300 Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> wrote: >> >>> If start_code / end_code pointers are screwed then "VmExe" could be bigger >>> than total executable virtual memory and "VmLib" becomes negative: >>> >>> VmExe: 294320 kB >>> VmLib: 18446744073709327564 kB >>> >>> VmExe and VmLib documented as text segment and shared library code size. >>> >>> Now their sum will be always equal to mm->exec_vm which sums size of >>> executable and not writable and not stack areas. >> >> When does this happen? What causes start_code/end_code to get "screwed"? > > I don't know exactly what happened. > I've seen this for huge (>2Gb) statically linked binary which has whole world inside. > > For it start_code .. end_code range also covers one of rodata sections. > Probably this is bug in customized linker, elf loader or both. > > Anyway CONFIG_CHECKPOINT_RESTORE allows to change these pointers, > thus we cannot trust them without validation. Please add this to changelog. I agree that it's better/safer after your patch. These counters are fundamentally heuristics so we can't guarantee "proper" values for weird binaries. exec_vm OTOH is an objective value so it makes sense to use it as a safe boundary. Acked-by: Vlastimil Babka <vbabka@xxxxxxx> >> >> When these pointers are screwed, the result of end_code-start_code can >> still be wrong while not necessarily being negative, yes? In which >> case we'll still display incorrect output? >> > > Here we split exec_vm into main code segment and libraries. > > Range start_code .. end_code declared as main code segment. > In my case it's bigger than exec_vm, so libraries have to be negative. > > After my patch libraries will be 0 and whole exec_vm show as VmExe. > At least sum VmExe + VmLib stays correct and both of them sane. > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
