[PATCH 0/8] x86: A round of x86 segmentation improvements

From: Andy Lutomirski
Date: Tue Apr 26 2016 - 15:23:39 EST


Hi all-

This is preparation for enabling FSGSBASE and fixing FS/GS switching
better than my last attempt.

It cleans up the code, fixes two more holes in X86_BUG_NULL_SEG
handling (loadsegment(fs, val) and load_gs_index(val) failure
handling), and makes set_thread_area behave in a well-defined
manner.

With these patches applied, modify_ldt should be the last remaining
way for a user thread to get its cached descriptors out of sync with
memory, except in the 64-bit FS/GS < 3 case. I'll fix modify_ldt as
well, but those patches will come later.

I'm sending these now because they seem to be good improvements on
their own and it'll help avoid a monster patch series down the road.

Tested on x86_32 with and without lazy GS and on x86_64.

Andy Lutomirski (8):
x86/asm: Stop depending on ptrace.h in alternative.h
x86/asm: Make asm/alternative.h safe from assembly
x86/segments/64: When loadsegment(fs, ...) fails, clear the base
x86/segments/64: When load_gs_index fails, clear the base
x86/arch_prctl/64: Remove FSBASE/GSBASE < 4G optimization
x86/asm/64: Rename thread_struct's fs and gs to fsbase and gsbase
x86/tls: Synchronize segment registers in set_thread_area
selftests/x86/ldt_gdt: Test set_thread_area deletion of an active
segment

arch/x86/entry/entry_64.S | 6 +
arch/x86/include/asm/alternative.h | 35 +----
arch/x86/include/asm/elf.h | 6 +-
arch/x86/include/asm/kgdb.h | 2 +
arch/x86/include/asm/processor.h | 11 +-
arch/x86/include/asm/segment.h | 49 +++++--
arch/x86/include/asm/setup.h | 1 +
arch/x86/include/asm/text-patching.h | 40 ++++++
arch/x86/kernel/alternative.c | 1 +
arch/x86/kernel/cpu/common.c | 2 +-
arch/x86/kernel/jump_label.c | 1 +
arch/x86/kernel/kgdb.c | 1 +
arch/x86/kernel/kprobes/core.c | 1 +
arch/x86/kernel/kprobes/opt.c | 1 +
arch/x86/kernel/module.c | 1 +
arch/x86/kernel/process_64.c | 97 ++++---------
arch/x86/kernel/ptrace.c | 48 ++-----
arch/x86/kernel/tls.c | 42 ++++++
arch/x86/kernel/traps.c | 1 +
arch/x86/kvm/svm.c | 2 +-
arch/x86/mm/extable.c | 10 ++
tools/testing/selftests/x86/ldt_gdt.c | 250 ++++++++++++++++++++++++++++++++++
22 files changed, 446 insertions(+), 162 deletions(-)
create mode 100644 arch/x86/include/asm/text-patching.h

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2.5.5