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    SubjectRe: [RFC][PATCH 4/4] x86_32: Provide consistent pt_regs
    On Wed, May 08, 2019 at 09:49:05AM +0200, Peter Zijlstra wrote:
    > Currently pt_regs on x86_32 has an oddity in that kernel regs
    > (!user_mode(regs)) are short two entries (esp/ss). This means that any
    > code trying to use them (typically: regs->sp) needs to jump through
    > some unfortunate hoops.
    >
    > Change the entry code to fix this up and create a full pt_regs frame.
    >
    > This then simplifies:
    >
    > - ftrace
    > - kprobes
    > - stack unwinder
    > - ptrace
    > - kdump
    > - kgdb
    >
    > Hated-by: Linus Torvalds <torvalds@linux-foundation.org>
    > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    > ---
    > arch/x86/entry/entry_32.S | 105 ++++++++++++++++++++++++++++++++++----
    > arch/x86/include/asm/kexec.h | 17 ------
    > arch/x86/include/asm/ptrace.h | 17 ------
    > arch/x86/include/asm/stacktrace.h | 2
    > arch/x86/kernel/crash.c | 8 --
    > arch/x86/kernel/ftrace_32.S | 81 ++++++++++++++++-------------
    > arch/x86/kernel/kgdb.c | 8 --
    > arch/x86/kernel/kprobes/common.h | 4 -
    > arch/x86/kernel/kprobes/core.c | 29 ++++------
    > arch/x86/kernel/kprobes/opt.c | 20 ++++---
    > arch/x86/kernel/process_32.c | 16 +----
    > arch/x86/kernel/ptrace.c | 29 ----------
    > arch/x86/kernel/time.c | 3 -
    > arch/x86/kernel/unwind_frame.c | 32 +----------
    > arch/x86/kernel/unwind_orc.c | 2
    > 15 files changed, 181 insertions(+), 192 deletions(-)

    Very nice diffstat. This moves all the pain to the 32-bit entry code
    where it belongs.

    --
    Josh

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