linux/arch/hexagon/kernel
Jason Baron 909af768e8 coredump: remove VM_ALWAYSDUMP flag
The motivation for this patchset was that I was looking at a way for a
qemu-kvm process, to exclude the guest memory from its core dump, which
can be quite large.  There are already a number of filter flags in
/proc/<pid>/coredump_filter, however, these allow one to specify 'types'
of kernel memory, not specific address ranges (which is needed in this
case).

Since there are no more vma flags available, the first patch eliminates
the need for the 'VM_ALWAYSDUMP' flag.  The flag is used internally by
the kernel to mark vdso and vsyscall pages.  However, it is simple
enough to check if a vma covers a vdso or vsyscall page without the need
for this flag.

The second patch then replaces the 'VM_ALWAYSDUMP' flag with a new
'VM_NODUMP' flag, which can be set by userspace using new madvise flags:
'MADV_DONTDUMP', and unset via 'MADV_DODUMP'.  The core dump filters
continue to work the same as before unless 'MADV_DONTDUMP' is set on the
region.

The qemu code which implements this features is at:

  http://people.redhat.com/~jbaron/qemu-dump/qemu-dump.patch

In my testing the qemu core dump shrunk from 383MB -> 13MB with this
patch.

I also believe that the 'MADV_DONTDUMP' flag might be useful for
security sensitive apps, which might want to select which areas are
dumped.

This patch:

The VM_ALWAYSDUMP flag is currently used by the coredump code to
indicate that a vma is part of a vsyscall or vdso section.  However, we
can determine if a vma is in one these sections by checking it against
the gate_vma and checking for a non-NULL return value from
arch_vma_name().  Thus, freeing a valuable vma bit.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Acked-by: Roland McGrath <roland@hack.frob.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Avi Kivity <avi@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-23 16:58:42 -07:00
..
asm-offsets.c Hexagon: Add configuration and makefiles for the Hexagon architecture. 2011-11-01 07:34:21 -07:00
dma.c Hexagon: Provide DMA implementation 2011-11-01 07:34:20 -07:00
head.S Hexagon: Add startup code 2011-11-01 07:34:19 -07:00
hexagon_ksyms.c Hexagon: Export ksyms defined in assembly files. 2011-11-01 07:34:19 -07:00
init_task.c Hexagon: Add init_task and process functions 2011-11-01 07:34:19 -07:00
irq_cpu.c Hexagon: Add interrupts 2011-11-01 07:34:19 -07:00
kgdb.c Hexagon: kgdb support files 2011-11-01 07:34:21 -07:00
Makefile Hexagon: Add configuration and makefiles for the Hexagon architecture. 2011-11-01 07:34:21 -07:00
module.c Hexagon: Support dynamic module loading. 2011-11-01 07:34:19 -07:00
process.c Hexagon: Add init_task and process functions 2011-11-01 07:34:19 -07:00
ptrace.c Hexagon: Add ptrace support 2011-11-01 07:34:19 -07:00
reset.c Hexagon: Add startup code 2011-11-01 07:34:19 -07:00
setup.c Hexagon: Add startup code 2011-11-01 07:34:19 -07:00
signal.c Hexagon: use set_current_blocked() and block_sigmask() 2012-03-23 16:58:41 -07:00
smp.c sched: Cleanup cpu_active madness 2012-03-12 20:43:15 +01:00
stacktrace.c Hexagon: Add basic stacktrace functionality for Hexagon architecture. 2011-11-01 07:34:21 -07:00
syscall.c
syscalltab.c
time.c Hexagon: Add time and timer functions 2011-11-01 07:34:19 -07:00
topology.c Hexagon: Add SMP support 2011-11-01 07:34:20 -07:00
trampoline.S Hexagon: Add signal functions 2011-11-01 07:34:19 -07:00
traps.c Hexagon: Provide basic debugging and system trap support. 2011-11-01 07:34:19 -07:00
vdso.c coredump: remove VM_ALWAYSDUMP flag 2012-03-23 16:58:42 -07:00
vm_entry.S Hexagon: Add hypervisor interface 2011-11-01 07:34:19 -07:00
vm_events.c Hexagon: Add hypervisor interface 2011-11-01 07:34:19 -07:00
vm_init_segtable.S Hexagon: Add hypervisor interface 2011-11-01 07:34:19 -07:00
vm_ops.S Hexagon: Add hypervisor interface 2011-11-01 07:34:19 -07:00
vm_switch.S Hexagon: Add hypervisor interface 2011-11-01 07:34:19 -07:00
vm_vectors.S Hexagon: Add hypervisor interface 2011-11-01 07:34:19 -07:00
vmlinux.lds.S Hexagon: Add configuration and makefiles for the Hexagon architecture. 2011-11-01 07:34:21 -07:00