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path: root/arch/mips/kernel/vdso.c
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2012-03-23coredump: remove VM_ALWAYSDUMP flagJason Baron
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>
2010-07-26MIPS: Make init_vdso a subsys_initcall.David Daney
Quoting from Jiri Slaby's patch of a similar nature for x86: When initrd is in use and a driver does request_module() in its module_init (i.e. __initcall or device_initcall), a modprobe process is created with VDSO mapping. But VDSO is inited even in __initcall, i.e. on the same level (at the same time), so it may not be inited yet (link order matters). Move init_vdso up to subsys_initcall to avoid the issue. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Cc: David Daney <ddaney@caviumnetworks.com> Cc: Jiri Slaby <jslaby@suse.cz> Patchwork: http://patchwork.linux-mips.org/patch/1386/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2010-07-26MIPS: "Fix" useless 'init_vdso successfully' message.David Daney
In addition to being useless, it was mis-spelled. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Cc: David Daney <ddaney@caviumnetworks.com> Patchwork: http://patchwork.linux-mips.org/patch/1385/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2010-04-12MIPS: Preliminary VDSODavid Daney
This is a preliminary patch to add a vdso to all user processes. Still missing are ELF headers and .eh_frame information. But it is enough to allow us to move signal trampolines off of the stack. Note that emulation of branch delay slots in the FPU emulator still requires the stack. We allocate a single page (the vdso) and write all possible signal trampolines into it. The stack is moved down by one page and the vdso is mapped into this space. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Patchwork: http://patchwork.linux-mips.org/patch/975/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>