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SubjectRe: [PATCH 0/4] x86: clean up orig_ax handling

* Roland McGrath <roland@redhat.com> wrote:

> Here is the aforementioned other tack on this.
>
> I said earlier that getreg() (i.e. 64-bit ptrace/core-dump fetches)
> should sign-extend the low 32 bits of orig_ax up. But I've changed my
> mind. It's true that today you can store 0xffffffff via either 64-bit
> ptrace or 32-bit ptrace and then read back -1 via 64-bit ptrace. (This
> wasn't always so, and so we can hope that no debugger really depends on
> it.) What seems more important is that tracing and core dumps correctly
> show the full orig_ax value incoming in %rax from userland, since
> %rax=__NR_foo|(1UL<<32) behaves differently (i.e. -ENOSYS) than
> %eax=_NR_foo in actual fact when user-mode does "syscall" with those
> values. In a bogon case like that, you would like to have traces/dumps
> tell you why the task is not making a proper syscall rather than lie
> about what register bits it entered the kernel with.
>
> Patches 1-3 change no ptrace-tests outcomes, i.e. don't regress on the
> test cases that went with the original sign-extension changes. They
> reintroduce e.g. the ability to blindly read and write back the whole
> regset when at syscall-entry tracing with %rax=__NR_foo|(1UL<<32) and
> have that fail with -ENOSYS as it would without tracing rather than
> perturb the tracee to call sys_foo instead. (Not that this is useful.)
>
> Patch 4 does Linus's fix for the outstanding bug. I've verified it works.
>
>
> Thanks,
> Roland
> ---
> The following changes since commit 7fa07729e439a6184bd824746d06a49cca553f15:
> Linus Torvalds (1):
> Merge branch 'perf-fixes-for-linus' of git://git.kernel.org/.../tip/linux-2.6-tip
>
> are available in the git repository at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/frob/linux-2.6-roland.git x86/orig_ax
>
> Roland McGrath (4):
> asm-generic: syscall_get_nr returns int
> x86: syscall_get_nr returns int
> x86: ptrace: do not sign-extend orig_ax on write
> x86: ptrace: set TS_COMPAT when 32-bit ptrace sets orig_eax>=0
>
> arch/x86/include/asm/syscall.h | 14 +++++++-------
> arch/x86/kernel/ptrace.c | 21 ++++++++-------------
> include/asm-generic/syscall.h | 8 ++++++--
> 3 files changed, 21 insertions(+), 22 deletions(-)

Linus, this series looks good to me. Do you want to pull this directly
or should we test this for a few days in the x86 tree? (either solution
is fine to me)

Ingo


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