x86/entry/64: Open-code switch_to_thread_stack()

Open-code the two instances which called 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,
and update the commentary to reflect what we are actually doing here.

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/20180220210113.6725-7-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 42a4b65..d5c7f18 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -538,17 +538,48 @@ 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 helper function.
+ *
+ * Entry runs with interrupts off. Stack layout at entry:
+ * +----------------------------------------------------+
+ * | regs->ss                                          |
+ * | regs->rsp                                         |
+ * | regs->eflags                                      |
+ * | regs->cs                                          |
+ * | regs->ip                                          |
+ * +----------------------------------------------------+
+ * | regs->orig_ax = ~(interrupt number)               |
+ * +----------------------------------------------------+
+ * | return address                                    |
+ * +----------------------------------------------------+
  */
-.macro DO_SWITCH_TO_THREAD_STACK
+ENTRY(interrupt_entry)
+       UNWIND_HINT_FUNC
+       ASM_CLAC
+       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
 
        pushq   7*8(%rdi)               /* regs->ss */
        pushq   6*8(%rdi)               /* regs->rsp */
@@ -560,25 +591,6 @@ END(irq_entries_start)
        UNWIND_HINT_FUNC
 
        movq    (%rdi), %rdi
-.endm
-
-/*
- * Interrupt entry/exit.
- *
- * Interrupt entry points save only callee clobbered registers in fast path.
- *
- * Entry runs with interrupts off.
- */
-/* 8(%rsp): ~(interrupt number) */
-ENTRY(interrupt_entry)
-       UNWIND_HINT_FUNC
-       ASM_CLAC
-       cld
-
-       testb   $3, CS-ORIG_RAX+8(%rsp)
-       jz      1f
-       SWAPGS
-       DO_SWITCH_TO_THREAD_STACK
 1:
 
        PUSH_AND_CLEAR_REGS save_ret=1
@@ -592,7 +604,7 @@ ENTRY(interrupt_entry)
         *
         * We need to tell lockdep that IRQs are off.  We can't do this until
         * we fix gsbase, and we should do it before enter_from_user_mode
-        * (which can take locks).  Since TRACE_IRQS_OFF idempotent,
+        * (which can take locks).  Since TRACE_IRQS_OFF is idempotent,
         * the simplest way to handle it is to just call it twice if
         * we enter from user mode.  There's no reason to optimize this since
         * TRACE_IRQS_OFF is a no-op if lockdep is off.
@@ -609,6 +621,9 @@ ENTRY(interrupt_entry)
        ret
 END(interrupt_entry)
 
+
+/* Interrupt entry/exit. */
+
        /*
         * The interrupt stubs push (~vector+0x80) onto the stack and
         * then jump to common_interrupt.
@@ -878,17 +893,6 @@ 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)
 
-#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
-
-       DO_SWITCH_TO_THREAD_STACK
-
-       ret
-END(switch_to_thread_stack)
-#endif
-
 .macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1
 ENTRY(\sym)
        UNWIND_HINT_IRET_REGS offset=\has_error_code*8

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 364ea4a..e811dd9 100644 (file)
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -347,10 +347,23 @@ ENTRY(entry_INT80_compat)
         */
        movl    %eax, %eax
 
+       /* switch to thread stack expects orig_ax and rdi to be pushed */
        pushq   %rax                    /* pt_regs->orig_ax */
+       pushq   %rdi                    /* pt_regs->di */
+
+       /* 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
+
+       pushq   6*8(%rdi)               /* regs->ss */
+       pushq   5*8(%rdi)               /* regs->rsp */
+       pushq   4*8(%rdi)               /* regs->eflags */
+       pushq   3*8(%rdi)               /* regs->cs */
+       pushq   2*8(%rdi)               /* regs->ip */
+       pushq   1*8(%rdi)               /* regs->orig_ax */
 
-       /* switch to thread stack expects orig_ax to be pushed */
-       call    switch_to_thread_stack
+       movq    (%rdi), %rdi            /* restore %rdi */
 
        pushq   %rdi                    /* pt_regs->di */
        pushq   %rsi                    /* pt_regs->si */