[patch V4 part 5 26/31] x86/entry/64: Remove IRQ stack switching ASM

Thomas Gleixner
2020-05-05T14:17:54Z

arch/x86/entry/entry_64.S | 96 ----------------------------------------------
1 file changed, 96 deletions(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -371,102 +371,6 @@ SYM_CODE_END(ret_from_fork)
#endif
.endm

-/*
- * Enters the IRQ stack if we're not already using it. NMI-safe. Clobbers
- * flags and puts old RSP into old_rsp, and leaves all other GPRs alone.
- * Requires kernel GSBASE.
- *
- * The invariant is that, if irq_count != -1, then the IRQ stack is in use.
- */
-.macro ENTER_IRQ_STACK regs=1 old_rsp save_ret=0
- DEBUG_ENTRY_ASSERT_IRQS_OFF
-
- .if \save_ret
- /*
- * If save_ret is set, the original stack contains one additional
- * entry -- the return address. Therefore, move the address one
- * entry below %rsp to \old_rsp.
- */
- leaq 8(%rsp), \old_rsp
- .else
- movq %rsp, \old_rsp
- .endif
-
- .if \regs
- UNWIND_HINT_REGS base=\old_rsp
- .endif
-
- incl PER_CPU_VAR(irq_count)
- jnz .Lirq_stack_push_old_rsp_\@
-
- /*
- * Right now, if we just incremented irq_count to zero, we've
- * claimed the IRQ stack but we haven't switched to it yet.
- *
- * If anything is added that can interrupt us here without using IST,
- * it must be *extremely* careful to limit its stack usage. This
- * could include kprobes and a hypothetical future IST-less #DB
- * handler.
- *
- * The OOPS unwinder relies on the word at the top of the IRQ
- * stack linking back to the previous RSP for the entire time we're
- * on the IRQ stack. For this to work reliably, we need to write
- * it before we actually move ourselves to the IRQ stack.
- */
-
- movq \old_rsp, PER_CPU_VAR(irq_stack_backing_store + IRQ_STACK_SIZE - 8)
- movq PER_CPU_VAR(hardirq_stack_ptr), %rsp
-
-#ifdef CONFIG_DEBUG_ENTRY
- /*
- * If the first movq above becomes wrong due to IRQ stack layout
- * changes, the only way we'll notice is if we try to unwind right
- * here. Assert that we set up the stack right to catch this type
- * of bug quickly.
- */
- cmpq -8(%rsp), \old_rsp
- je .Lirq_stack_okay\@
- ud2
- .Lirq_stack_okay\@:
-#endif
-
-.Lirq_stack_push_old_rsp_\@:
- pushq \old_rsp
-
- .if \regs
- UNWIND_HINT_REGS indirect=1
- .endif
-
- .if \save_ret
- /*
- * Push the return address to the stack. This return address can
- * be found at the "real" original RSP, which was offset by 8 at
- * the beginning of this macro.
- */
- pushq -8(\old_rsp)
- .endif
-.endm
-
-/*
- * Undoes ENTER_IRQ_STACK.
- */
-.macro LEAVE_IRQ_STACK regs=1
- DEBUG_ENTRY_ASSERT_IRQS_OFF
- /* We need to be off the IRQ stack before decrementing irq_count. */
- popq %rsp
-
- .if \regs
- UNWIND_HINT_REGS
- .endif
-
- /*
- * As in ENTER_IRQ_STACK, irq_count == 0, we are still claiming
- * the irq stack but we're not on it.
- */
-
- decl PER_CPU_VAR(irq_count)
-.endm
-
/**
* idtentry_body - Macro to emit code calling the C function
* @cfunc: C function to be called