Recent linux kernels enable KASLR to randomize phys/virt memory addresses. This series aims to provide enough information in qemu dumps so that crash utility can work with randomized kernel too (it hasn't been tested on other archs than x86 though, help welcome).
The vmcoreinfo device is an emulated ACPI device that exposes a 4k memory range to the guest to store various informations useful to debug the guest OS. (it is greatly inspired by the VMGENID device implementation). The version field with value 0 is meant to give paddr/size of the VMCOREINFO ELF PT_NOTE, other values can be used for different purposes or OSes. (note: some wanted to see pvpanic somehow merged with this device, I have no clear idea how to do that, nor do I think this is a good idea since the devices are quite different, used at different time for different purposes. And it can be done as a future iteration if it is appropriate, feel free to send patches) Crash 7.1.9 will parse the "phys_base" value from the VMCOREINFO note, and thus will work with KASLR-dump produced by this series. By priority, VMCOREINFO "phys_base" value is the most accurate. If not available, qemu will keep the current guessed value. The series implements the VMCOREINFO note addition in qemu ELF/kdump, as well as the python scripts/dump-guest-memory.py. To test: Compile and run a guest kernel with CONFIG_RANDOMIZE_BASE=y. Run qemu with -device vmcoreinfo. Load the experimental vmcoreinfo module in guest https://github.com/elmarco/vmgenid-test/blob/master/qemuvmci-test.c. Produce an ELF dump: { "execute": "dump-guest-memory", "arguments": { "protocol": "file:dump", "paging": false } } Produce a kdump: { "execute": "dump-guest-memory", "arguments": { "protocol": "file:dump", "paging": false, "format": "kdump-zlib" } } Or with (gdb) dump-guest-memory, with scripts/dump-guest-memory.py script. Analyze with crash >= 7.1.9 $ crash vmlinux dump Marc-André Lureau (7): vmgenid: replace x-write-pointer-available hack acpi: add vmcoreinfo device tests: add simple vmcoreinfo test dump: add vmcoreinfo ELF note kdump: add vmcoreinfo ELF note scripts/dump-guest-memory.py: add vmcoreinfo MAINTAINERS: add Dump maintainers scripts/dump-guest-memory.py | 32 ++++++ include/hw/acpi/aml-build.h | 1 + include/hw/acpi/bios-linker-loader.h | 2 + include/hw/acpi/vmcoreinfo.h | 37 ++++++ include/hw/compat.h | 4 - include/sysemu/dump.h | 2 + dump.c | 165 ++++++++++++++++++++++++++- hw/acpi/aml-build.c | 2 + hw/acpi/bios-linker-loader.c | 6 + hw/acpi/vmcoreinfo.c | 214 +++++++++++++++++++++++++++++++++++ hw/acpi/vmgenid.c | 9 +- hw/i386/acpi-build.c | 14 +++ tests/vmcoreinfo-test.c | 130 +++++++++++++++++++++ MAINTAINERS | 7 ++ default-configs/arm-softmmu.mak | 1 + default-configs/i386-softmmu.mak | 1 + default-configs/x86_64-softmmu.mak | 1 + docs/specs/vmcoreinfo.txt | 138 ++++++++++++++++++++++ hw/acpi/Makefile.objs | 1 + tests/Makefile.include | 2 + 20 files changed, 753 insertions(+), 16 deletions(-) create mode 100644 include/hw/acpi/vmcoreinfo.h create mode 100644 hw/acpi/vmcoreinfo.c create mode 100644 tests/vmcoreinfo-test.c create mode 100644 docs/specs/vmcoreinfo.txt -- 2.13.1.395.gf7b71de06
