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Subject[PATCH 0/6 v3] sycalls: Remove args i and n from syscall_get_arguments()
[ Looking for acks ]

Two and a half years ago I sent out 3 patches and a title letter that
had this[1]:

At Linux Plumbers, Andy Lutomirski approached me to tell me that the
syscall_get_arguments() implementation in x86 was horrible and gcc
certainly gets it wrong. He said that since the tracepoints only pass
in 0 and 6 for i and n repectively, it should be optimized for that case.
Inspecting the kernel, I discovered that all users pass in 0 for i and
only one file passing in something other than 6 for the number of arguments.
That code happens to be my own code used for the special syscall tracing.
That can easily be converted to just using 0 and 6 as well, and only copying
what is needed. Which is probably the faster path anyway for that case.

I haven't run the numbers (I can do that when I get some time), but since
pretty much all use cases use 0 and 6 and that would allow these functions
not to need strange logic to handle odd cases, I think this is still a win.

It received positive comments but also Linus asked to remove the separate
arg pointers and replace them with a single structure and fill that
instead. But for some reason, this got pushed aside and forgotten (probably,
had to do with the fact that I left Red Hat shortly after this).

Recently, it was brought back up again[2] and I decided to dust off these
patches and resubmit them. I also added one more patch to do the same
for syscall_set_arguments() that I did for syscall_get_arguments() even
though syscall_set_arguments() currently (and never has) had any callers.
But we are told that in the near future it may have one.

The changes do optimize the logic a little, but for most archs I just kept
the same logic (loops and such) as I don't have a way to test it, and
didn't want to break the logic.

I added a new struct syscall_info that holds seccomp_data and also
includes a stack pointer (sp) field. I would change seccomp_data,
but because its in include/uapi/linux/seccomp.h I didn't want to
touch it and break userspace. Perhaps we could add the field at the
end, but I didn't want to chance it (unless others say its OK).

I ran these through zero-day-bot and compiled tested these changes for
all architectures except for csky which I do not have a cross compiler
for.

Note the following archs fail normal builds, but they fail the same
with these patches:

arc
h8300
parisc64

Note, you may notice that I have "(Red Hat)" as the author of the
first three patches (even though they are signed off by "(VMware)").
This is because those patches were originally written while I was
working for Red Hat. But as I forward ported them while working for
VMware, my signed-off-by reflects that.

[1] - https://lore.kernel.org/lkml/20161107212634.529267342@goodmis.org/T/#u
[2] - https://lore.kernel.org/lkml/20190326151244.GC16837@redhat.com/T/#u


Changes since v2:

- Added Dmitry's two patches to fix riscv and csky
- Rebased to handle the two new patches

Dmitry V. Levin (2):
riscv: Fix syscall_get_arguments() and syscall_set_arguments()
csky: Fix syscall_get_arguments() and syscall_set_arguments()

Steven Rostedt (Red Hat) (3):
ptrace: Remove maxargs from task_current_syscall()
tracing/syscalls: Pass in hardcoded 6 into syscall_get_arguments()
syscalls: Remove start and number from syscall_get_arguments() args

Steven Rostedt (VMware) (1):
syscalls: Remove start and number from syscall_set_arguments() args

----
arch/arc/include/asm/syscall.h | 7 +-
arch/arm/include/asm/syscall.h | 47 ++---------
arch/arm64/include/asm/syscall.h | 46 ++---------
arch/c6x/include/asm/syscall.h | 79 ++++---------------
arch/csky/include/asm/syscall.h | 26 ++-----
arch/h8300/include/asm/syscall.h | 34 ++------
arch/hexagon/include/asm/syscall.h | 4 +-
arch/ia64/include/asm/syscall.h | 13 +---
arch/ia64/kernel/ptrace.c | 7 +-
arch/microblaze/include/asm/syscall.h | 8 +-
arch/mips/include/asm/syscall.h | 3 +-
arch/mips/kernel/ptrace.c | 2 +-
arch/nds32/include/asm/syscall.h | 62 +++------------
arch/nios2/include/asm/syscall.h | 84 ++++----------------
arch/openrisc/include/asm/syscall.h | 12 +--
arch/parisc/include/asm/syscall.h | 30 ++-----
arch/powerpc/include/asm/syscall.h | 15 ++--
arch/riscv/include/asm/syscall.h | 24 ++----
arch/s390/include/asm/syscall.h | 28 +++----
arch/sh/include/asm/syscall_32.h | 47 +++--------
arch/sh/include/asm/syscall_64.h | 8 +-
arch/sparc/include/asm/syscall.h | 11 ++-
arch/um/include/asm/syscall-generic.h | 78 +++----------------
arch/x86/include/asm/syscall.h | 142 ++++++++--------------------------
arch/xtensa/include/asm/syscall.h | 33 ++------
fs/proc/base.c | 17 ++--
include/asm-generic/syscall.h | 21 ++---
include/linux/ptrace.h | 11 ++-
include/trace/events/syscalls.h | 2 +-
kernel/seccomp.c | 2 +-
kernel/trace/trace_syscalls.c | 9 ++-
lib/syscall.c | 57 ++++++--------
32 files changed, 247 insertions(+), 722 deletions(-)

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