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.
Along the way, a couple of real fixes came from this as the
syscall_get_arguments() function was incorrect for csky and riscv.
x86 has been optimized to for the new interface that removes the variable
number of arguments, but the other architectures could still use some
loving and take more advantage of the simpler interface.
-----BEGIN PGP SIGNATURE-----
iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCXKdi7RQccm9zdGVkdEBn
b29kbWlzLm9yZwAKCRAp5XQQmuv6qjtiAQDaZbFaSgEbs99jjuAPDSZ0li8dyUOC
3KS5TyuLw+fEaAD/QZnKjplVFAfA5FxrABZ0ioIKDON4nLyESEb+xCv0gA4=
=dTuo
-----END PGP SIGNATURE-----
Merge tag 'trace-5.1-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull syscall-get-arguments cleanup and fixes from Steven Rostedt:
"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.
Along the way, a couple of real fixes came from this as the
syscall_get_arguments() function was incorrect for csky and riscv.
x86 has been optimized to for the new interface that removes the
variable number of arguments, but the other architectures could still
use some loving and take more advantage of the simpler interface"
* tag 'trace-5.1-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
syscalls: Remove start and number from syscall_set_arguments() args
syscalls: Remove start and number from syscall_get_arguments() args
csky: Fix syscall_get_arguments() and syscall_set_arguments()
riscv: Fix syscall_get_arguments() and syscall_set_arguments()
tracing/syscalls: Pass in hardcoded 6 into syscall_get_arguments()
ptrace: Remove maxargs from task_current_syscall()
970b766cfd