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@xxxxxxxxxxx/T/#u [2] - https://lore.kernel.org/lkml/20190326151244.GC16837@xxxxxxxxxx/T/#u 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(-)
