Commit-ID: 24d978b76ffd20ecff8a8d1c21b16fe740f8b119 Gitweb: http://git.kernel.org/tip/24d978b76ffd20ecff8a8d1c21b16fe740f8b119 Author: Andy Lutomirski <[email protected]> AuthorDate: Thu, 28 Jan 2016 15:11:27 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Fri, 29 Jan 2016 09:46:38 +0100
x86/entry/64: Stop using int_ret_from_sys_call in ret_from_fork ret_from_fork is now open-coded and is no longer tangled up with the syscall code. This isn't so bad -- this adds very little code, and IMO the result is much easier to understand. Signed-off-by: Andy Lutomirski <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/a0747e2a5e47084655a1e96351c545b755c41fa7.1454022279.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/entry/entry_64.S | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index f7050a5..cb5d940 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -390,7 +390,6 @@ END(ptregs_\func) * rdi: prev task we switched from */ ENTRY(ret_from_fork) - LOCK ; btr $TIF_FORK, TI_flags(%r8) pushq $0x0002 @@ -398,28 +397,32 @@ ENTRY(ret_from_fork) call schedule_tail /* rdi: 'prev' task parameter */ - RESTORE_EXTRA_REGS - testb $3, CS(%rsp) /* from kernel_thread? */ + jnz 1f /* - * By the time we get here, we have no idea whether our pt_regs, - * ti flags, and ti status came from the 64-bit SYSCALL fast path, - * the slow path, or one of the 32-bit compat paths. - * Use IRET code path to return, since it can safely handle - * all of the above. + * We came from kernel_thread. This code path is quite twisted, and + * someone should clean it up. + * + * copy_thread_tls stashes the function pointer in RBX and the + * parameter to be passed in RBP. The called function is permitted + * to call do_execve and thereby jump to user mode. */ - jnz int_ret_from_sys_call + movq RBP(%rsp), %rdi + call *RBX(%rsp) + movl $0, RAX(%rsp) /* - * We came from kernel_thread - * nb: we depend on RESTORE_EXTRA_REGS above + * Fall through as though we're exiting a syscall. This makes a + * twisted sort of sense if we just called do_execve. */ - movq %rbp, %rdi - call *%rbx - movl $0, RAX(%rsp) - RESTORE_EXTRA_REGS - jmp int_ret_from_sys_call + +1: + movq %rsp, %rdi + call syscall_return_slowpath /* returns with IRQs disabled */ + TRACE_IRQS_ON /* user mode is traced as IRQS on */ + SWAPGS + jmp restore_regs_and_iret END(ret_from_fork) /*
