On Sun, Feb 18, 2018 at 01:31:16PM +0100, Dominik Brodowski wrote: > Open-code the two instances which used switch_to_thread_stack. This > allows us to remove the wrapper around DO_SWITCH_TO_THREAD_STACK. > > While at it, update the UNWIND hint to reflect where the IRET frame is. > > Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net> > --- > arch/x86/entry/entry_64.S | 59 > ++++++++++++++++------------------------ > arch/x86/entry/entry_64_compat.S | 19 ++++++++++++- > 2 files changed, 42 insertions(+), 36 deletions(-) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index 0ac2b4865d58..fa61be457082 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -539,17 +539,36 @@ END(irq_entries_start) > .endm > > /* > - * Switch to the thread stack. This is called with the IRET frame and > - * orig_ax on the stack. (That is, RDI..R12 are not on the stack and > - * space has not been allocated for them.) > + * Interrupt entry/exit. > + * > + * Interrupt entry points save only callee clobbered registers in fast path. > + * > + * Entry runs with interrupts off. > */
These comments aren't really accurate anymore: - The function only handles interrupt entry, not exit. - All registers are saved, there is no fast path. > -.macro DO_SWITCH_TO_THREAD_STACK > +/* 8(%rsp): ~(interrupt number) */ > +ENTRY(interrupt_helper) "interrupt_helper" is a bit vague, how about "interrupt_entry"? That better describes its purpose and also makes it more analagous to paranoid_entry() and error_entry(). > + UNWIND_HINT_FUNC > + cld > + > + testb $3, CS-ORIG_RAX+8(%rsp) > + jz 1f > + SWAPGS > + > + /* > + * Switch to the thread stack. The IRET frame and orig_ax are > + * on the stack, as well as the return address. RDI..R12 are > + * not (yet) on the stack and space has not (yet) been > + * allocated for them. > + */ > pushq %rdi > + > /* Need to switch before accessing the thread stack. */ > SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi > movq %rsp, %rdi > movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp > - UNWIND_HINT sp_offset=16 sp_reg=ORC_REG_DI > + /* We have RDI, return address, and orig_ax on the stack on > + * top of the IRET frame. That means offset=24 */ > + UNWIND_HINT_IRET_REGS base=%rdi offset=24 The hint looks right, though the comment formatting isn't in the kernel style. > diff --git a/arch/x86/entry/entry_64_compat.S > b/arch/x86/entry/entry_64_compat.S > index 364ea4a207be..5b9503c7148d 100644 > --- a/arch/x86/entry/entry_64_compat.S > +++ b/arch/x86/entry/entry_64_compat.S > @@ -350,7 +350,24 @@ ENTRY(entry_INT80_compat) > pushq %rax /* pt_regs->orig_ax */ > > /* switch to thread stack expects orig_ax to be pushed */ > - call switch_to_thread_stack > + pushq %rdi > + > + /* Need to switch before accessing the thread stack. */ > + SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi > + movq %rsp, %rdi > + movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp > + /* We have RDI and orig_ax on the stack on top of the IRET frame. > + * That means offset=16 */ > + UNWIND_HINT_IRET_REGS base=%rdi offset=16 Objtool doesn't scan this file yet, so no hints needed here yet. Adding it to my TODO list... -- Josh
