Messages in this thread | | | Date | Mon, 7 Dec 2015 19:50:55 -0500 | Subject | Re: [PATCH 07/12] x86/entry/64: Always run ptregs-using syscalls on the slow path | From | Brian Gerst <> |
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On Mon, Dec 7, 2015 at 4:51 PM, Andy Lutomirski <luto@kernel.org> wrote: > 64-bit syscalls currently have an optimization in which they are > called with partial pt_regs. A small handful require full pt_regs. > > In the 32-bit and compat cases, I cleaned this up by forcing full > pt_regs for all syscalls. The performance hit doesn't really matter. > > I want to clean up the 64-bit case as well, but I don't want to hurt > fast path performance. To do that, I want to force the syscalls > that use pt_regs onto the slow path. This will enable us to make > slow path syscalls be real ABI-compliant C functions. > > Use the new syscall entry qualification machinery for this. > stub_clone is now stub_clone/ptregs. > > The next patch will eliminate the stubs, and we'll just have > sys_clone/ptregs.
I've got an idea on how to do this without the duplicate syscall table.
ptregs_foo: leaq sys_foo(%rip), %rax jmp stub_ptregs_64
stub_ptregs_64: testl $TS_EXTRAREGS, <current->ti_status> jnz 1f SAVE_EXTRA_REGS call *%rax RESTORE_EXTRA_REGS ret 1: call *%rax
-- Brian Gerst
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