Entry stuff, in decent shape now

This sets up stack switching, including for SYSCALL. I think it's in decent shape.

Known issues:
- KASAN is likely to be busted. This could be fixed either by teaching KASAN that cpu_entry_area contains valid stacks (I have no clue how to go about doing this) or by rigging up the IST entry code to switch RSP to point to the direct-mapped copy of the stacks before calling into non-KASAN-excluded C code.

- 32-bit kernels are failing the sigreturn_32 test. But they're also failing without the patches, so I'm not sure this is a bug in the series per se. Needs further investigation. (Off the top of my head, this could be further fallout from Thomas's IDT rework.)

- I think we're going to want a way to turn the stack switching on and off either at boot time or at runtime. It should be fairly straightforward to make it work.

- I think the ORC unwinder isn't so good at dealing with stack overflows. It bails too early (I think), resulting in lots of ? entries. This isn't a regression with this series -- it's just something that could be improved.

Changes:
- This is quite massively changed from last time.
- 32-bit seems to build and mostly work
- KASAN is less broken now

Andy Lutomirski (16):
x86/asm/64: Allocate and enable the SYSENTER stack x86/dumpstack: Add get_stack_info() support for the SYSENTER stack x86/gdt: Put per-cpu GDT remaps in ascending order x86/fixmap: Generalize the GDT fixmap mechanism
x86/asm: Fix assumptions that the HW TSS is at the beginning of
cpu_tss
x86/dumpstack: Handle stack overflow on all stacks x86/asm: Move SYSENTER_stack to the beginning of struct tss_struct x86/asm: Remap the TSS into the cpu entry area x86/asm/64: Separate cpu_current_top_of_stack from TSS.sp0 x86/espfix/64: Stop assuming that pt_regs is on the entry stack x86/asm/64: Use a percpu trampoline stack for IDT entries x86/asm/64: Return to userspace from the trampoline stack x86/entry/64: Create a percpu SYSCALL entry trampoline x86/irq: Remove an old outdated comment about context tracking races x86/irq/64: In the stack overflow warning, print the offending IP x86/entry/64: Move the IST stacks into cpu_entry_area

 arch/x86/entry/entry_32.S          |   6 +-
 arch/x86/entry/entry_64.S          | 177 +++++++++++++++++++++++++++++++++----
 arch/x86/entry/entry_64_compat.S   |   6 +-
 arch/x86/include/asm/desc.h        |  11 +--
 arch/x86/include/asm/fixmap.h      |  55 +++++++++++-
 arch/x86/include/asm/processor.h   |  49 ++++++----
 arch/x86/include/asm/stacktrace.h  |   3 +
 arch/x86/include/asm/switch_to.h   |   2 +-
 arch/x86/include/asm/thread_info.h |   2 +-
 arch/x86/include/asm/traps.h       |   1 -
 arch/x86/kernel/asm-offsets.c      |   9 ++
 arch/x86/kernel/asm-offsets_32.c   |   5 --
 arch/x86/kernel/asm-offsets_64.c   |   1 +
 arch/x86/kernel/cpu/common.c       | 136 +++++++++++++++++++++-------
 arch/x86/kernel/doublefault.c      |  36 ++++----
 arch/x86/kernel/dumpstack.c        |  46 +++++++---
 arch/x86/kernel/dumpstack_32.c     |   6 ++
 arch/x86/kernel/dumpstack_64.c     |   6 ++
 arch/x86/kernel/irq.c              |  12 ---
 arch/x86/kernel/irq_64.c           |   4 +-
 arch/x86/kernel/process.c          |  12 ++-
 arch/x86/kernel/process_64.c       |   1 +
 arch/x86/kernel/traps.c            |  25 +++---
 arch/x86/kernel/vmlinux.lds.S      |  10 +++
 arch/x86/power/cpu.c               |  16 ++--
 arch/x86/xen/mmu_pv.c              |   2 +-
 26 files changed, 487 insertions(+), 152 deletions(-)

2.13.6