x86/entry/64: Move the switch_to_thread_stack() call to interrupt_entry()

We can also move the CLD, SWAPGS, and the switch_to_thread_stack() call
to the interrupt_entry() helper function. As we do not want call depths
of two, convert switch_to_thread_stack() to a macro.

However, switch_to_thread_stack() has another user in entry_64_compat.S,
which currently expects it to be a function. To keep the code changes
in this patch minimal, create a wrapper function.

The switch to a macro means that there is some binary code duplication
if CONFIG_IA32_EMULATION=y is enabled. Therefore, the size reduction
differs whether CONFIG_IA32_EMULATION is enabled or not:

CONFIG_IA32_EMULATION=y (-0.13k):
   text	   data	    bss	    dec	    hex	filename
  17158	      0	      0	  17158	   4306	entry_64.o-orig
  17028	      0	      0	  17028	   4284	entry_64.o

CONFIG_IA32_EMULATION=n (-0.27k):
   text	   data	    bss	    dec	    hex	filename
  17158	      0	      0	  17158	   4306	entry_64.o-orig
  16882	      0	      0	  16882	   41f2	entry_64.o

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: dan.j.williams@intel.com
Link: http://lkml.kernel.org/r/20180220210113.6725-4-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 7a6ae19962ec2df1d950dcf5698404b204915a6e..b45d76649eff46c0f45c1928b376de7160e3684e 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -537,6 +537,31 @@ END(irq_entries_start)
        decl    PER_CPU_VAR(irq_count)
 .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.)
+ */
+.macro DO_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
+       UNWIND_HINT sp_offset=16 sp_reg=ORC_REG_DI
+
+       pushq   7*8(%rdi)               /* regs->ss */
+       pushq   6*8(%rdi)               /* regs->rsp */
+       pushq   5*8(%rdi)               /* regs->eflags */
+       pushq   4*8(%rdi)               /* regs->cs */
+       pushq   3*8(%rdi)               /* regs->ip */
+       pushq   2*8(%rdi)               /* regs->orig_ax */
+       pushq   8(%rdi)                 /* return address */
+       UNWIND_HINT_FUNC
+
+       movq    (%rdi), %rdi
+.endm
+
 /*
  * Interrupt entry/exit.
  *
@@ -544,8 +569,16 @@ END(irq_entries_start)
  *
  * Entry runs with interrupts off.
  */
+/* 8(%rsp): ~(interrupt number) */
 ENTRY(interrupt_entry)
        UNWIND_HINT_FUNC
+       cld
+
+       testb   $3, CS-ORIG_RAX+8(%rsp)
+       jz      1f
+       SWAPGS
+       DO_SWITCH_TO_THREAD_STACK
+1:
 
        PUSH_AND_CLEAR_REGS save_ret=1
        ENCODE_FRAME_POINTER 8
@@ -577,14 +610,6 @@ END(interrupt_entry)
 
 /* 0(%rsp): ~(interrupt number) */
        .macro interrupt func
-       cld
-
-       testb   $3, CS-ORIG_RAX(%rsp)
-       jz      1f
-       SWAPGS
-       call    switch_to_thread_stack
-1:
-
        call    interrupt_entry
 
        UNWIND_HINT_REGS indirect=1
@@ -858,33 +883,16 @@ apicinterrupt IRQ_WORK_VECTOR                     irq_work_interrupt              smp_irq_work_interrupt
  */
 #define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss_rw) + (TSS_ist + ((x) - 1) * 8)
 
-/*
- * 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.)
- */
+#if defined(CONFIG_IA32_EMULATION)
+/* entry_64_compat.S::entry_INT80_compat expects this to be an ASM function */
 ENTRY(switch_to_thread_stack)
        UNWIND_HINT_FUNC
 
-       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
-
-       pushq   7*8(%rdi)               /* regs->ss */
-       pushq   6*8(%rdi)               /* regs->rsp */
-       pushq   5*8(%rdi)               /* regs->eflags */
-       pushq   4*8(%rdi)               /* regs->cs */
-       pushq   3*8(%rdi)               /* regs->ip */
-       pushq   2*8(%rdi)               /* regs->orig_ax */
-       pushq   8(%rdi)                 /* return address */
-       UNWIND_HINT_FUNC
+       DO_SWITCH_TO_THREAD_STACK
 
-       movq    (%rdi), %rdi
        ret
 END(switch_to_thread_stack)
+#endif
 
 .macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1
 ENTRY(\sym)