On Fri, 24 Nov 2023 at 06:01, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote:
Dimitri John Ledkov <dimitri.ledkov@xxxxxxxxxxxxx> writes:
I was working on how linux-libc-dev headers are shipped in Ubuntu and
stumbled upon seemingly unused and useless linux/a.out.h header. It
seems like it is an accidental leftover at this point.
How do you see that they are unused?
Are they never exported to userspace?
Are there any userspace programs that care?
Performing a quick debian code search I see chromium, qt6, ruby-rogue, hurd,
bazel_bootstrap, aboot, cde.
I can imagine all kinds of reasons old code could be using headers for a
historical format. Some of them are quite legitimate, and some of them
are quite silly. If it is old code like aboot it may be that it is
difficult to test any changes. If memory serves you have to flash your
firmware to change/test aboot.
Because showing userspace does not care about the definitions in a file
is a completely different problem then showing the kernel does not care
about the definitions I left them, last time I was working in this area.
Keeping headers that will never change is not cost to the kernel so it
doesn't hurt us to be nice to historical userspace.
My quick debian code search suggests that there are pieces of userspace
that still use linux/a.out.h. Are you seeing something I am not?
Do all of those pieces of code compile just fine with a.out.h missing?
I will recheck the above mentioned things again, but as far as I could
tell up to this point, is that things mostly use a.out.h provided by
glibc.
Separately, I can do this change in a test-rebuild of ubuntu archive
of all packages on amd64,. as that's the only Ubuntu arch that ships
linux/a.out.h.
As far as I can tell, the legacy userspace access to linux/a.out.h can
use glibc's a.out.h instead. But yes, it would be pain, if code
changes are required to things.
Eric
Dimitri John Ledkov (5):
alpha: remove a.out support from tools/objstrip
alpha: stop shipping a.out.h uapi headers
m68k: stop shipping a.out.h uapi headers
I think above three patches still can be merged in m68k & alpha trees.
x86: stop shipping a.out.h uapi headers
uapi: remove a.out.h uapi header
And these two need further validation now, based on Eric's input.
arch/alpha/boot/tools/objstrip.c | 52 +-----
arch/alpha/include/uapi/asm/a.out.h | 92 ----------
arch/m68k/include/uapi/asm/a.out.h | 21 ---
arch/x86/include/uapi/asm/a.out.h | 21 ---
include/uapi/Kbuild | 4 -
include/uapi/linux/a.out.h | 251 ----------------------------
6 files changed, 6 insertions(+), 435 deletions(-)
delete mode 100644 arch/alpha/include/uapi/asm/a.out.h
delete mode 100644 arch/m68k/include/uapi/asm/a.out.h
delete mode 100644 arch/x86/include/uapi/asm/a.out.h
delete mode 100644 include/uapi/linux/a.out.h
--
okurrr,
Dimitri
