linux-kernel - [PATCH v2 0/9] x86/entry/head: standardize the end of the stack

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Date:   Wed, 21 Sep 2016 16:03:58 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Nilay Vaish <nilayvaish@...il.com>
Subject: [PATCH v2 0/9] x86/entry/head: standardize the end of the stack

v2:
- keep 'restore_all' label in "x86/entry/head/32: use local labels"

---

Thanks to all the recent x86 entry code refactoring, most tasks' kernel
stacks start at the same offset right below their saved pt_regs,
regardless of which syscall was used to enter the kernel.  That creates
a nice convention which makes it straightforward to identify the end of
the stack, which can be useful [*] for the unwinder.

But there a few places where tasks don't yet follow the convention.
This patch set finishes the job.

[*] This will be useful for three upcoming proposed features:

- Detecting corrupt stacks in the unwinder (which will also be a force
  for ensuring this end of stack convention continues to be followed in
  the future).

- Printing all saved pt_regs on the stack during an oops/warning.

- Validating stacks in the livepatch consistency model.


Josh Poimboeuf (9):
  x86/entry/head/32: use local labels
  x86/entry/32: rename 'error_code' to 'common_exception'
  x86/entry/32: fix the end of the stack for newly forked tasks
  x86/head/32: fix the end of the stack for idle tasks
  x86/smp: fix initial idle stack location on 32-bit
  x86/asm/head: use a common function for starting CPUs
  x86/head: put real return address on idle task stack
  x86/head: fix the end of the stack for idle tasks
  x86: move _stext marker to before head code

 arch/x86/entry/entry_32.S     | 108 +++++++++++++++++++++++++-----------------
 arch/x86/kernel/head_32.S     |  49 +++++++++++--------
 arch/x86/kernel/head_64.S     |  42 ++++++++--------
 arch/x86/kernel/smpboot.c     |   4 +-
 arch/x86/kernel/vmlinux.lds.S |   2 +-
 5 files changed, 116 insertions(+), 89 deletions(-)

-- 
2.7.4