Entry stack switching

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

I'm fiddling with a patch to make the TSS remap read-only on 64-bit.

Known issues:
- 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 from v2:
- Tons of review comments
- The IDT entry stack switching code is less messy
- The last patch is new

Changes from v1:
- Fixed KASAN for real (as far as I can tell).
- Compiler errors due to my old hackish KASAN fix are gone.
- Context tracking lockdep errors are fixed (and maybe

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

Andy Lutomirski (19):
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/kasan/64: Teach KASAN about the cpu_entry_area 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to userspace from the trampoline stack x86/entry/64: Create a percpu SYSCALL entry trampoline x86/irq: Remove an old outdated comment about context tracking races x86/irq/64: In the stack overflow warning, print the offending IP x86/entry/64: Move the IST stacks into cpu_entry_area x86/entry/64: Remove the SYSENTER stack canary
x86/entry: Clean up SYSENTER_stack code

 arch/x86/entry/entry_32.S          |   6 +-
 arch/x86/entry/entry_64.S          | 170 ++++++++++++++++++++++++++++++++-----
 arch/x86/entry/entry_64_compat.S   |   7 +-
 arch/x86/include/asm/desc.h        |  11 +--
 arch/x86/include/asm/fixmap.h      |  58 ++++++++++++-
 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      |   7 ++
 arch/x86/kernel/asm-offsets_32.c   |   5 --
 arch/x86/kernel/asm-offsets_64.c   |   1 +
 arch/x86/kernel/cpu/common.c       | 133 +++++++++++++++++++++--------
 arch/x86/kernel/doublefault.c      |  36 ++++----
 arch/x86/kernel/dumpstack.c        |  42 ++++++---
 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          |  13 ++-
 arch/x86/kernel/process_64.c       |   1 +
 arch/x86/kernel/traps.c            |  27 +++---
 arch/x86/kernel/vmlinux.lds.S      |  10 +++
 arch/x86/mm/kasan_init_64.c        |  13 ++-
 arch/x86/power/cpu.c               |  16 ++--
 arch/x86/xen/mmu_pv.c              |   2 +-
 27 files changed, 473 insertions(+), 170 deletions(-)

2.13.6