x86,64: Simplify save_regs()

The save_regs function that saves the regs on low level
irq entry is complicated because of the fact it changes
its stack in the middle and also because it manipulates
data allocated in the caller frame and accesses there
are directly calculated from callee rsp value with the
return address in the middle of the way.

This complicates the static stack offsets calculation and
require more dynamic ones. It also needs a save/restore
of the function's return address.

To simplify and optimize this, turn save_regs() into a
macro.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 8a445a0c989e095bc84557861d4a4e73e09e3e90..b6b2e85454cf523e5f8bb95fc18f386df0d1bfe3 100644 (file)
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -297,27 +297,22 @@ ENDPROC(native_usergs_sysret64)
        .endm
 
 /* save partial stack frame */
-       .pushsection .kprobes.text, "ax"
-ENTRY(save_args)
-       XCPT_FRAME
+       .macro SAVE_ARGS_IRQ
        cld
-       /*
-        * start from rbp in pt_regs and jump over
-        * return address.
-        */
-       movq_cfi rdi, RDI+8-RBP
-       movq_cfi rsi, RSI+8-RBP
-       movq_cfi rdx, RDX+8-RBP
-       movq_cfi rcx, RCX+8-RBP
-       movq_cfi rax, RAX+8-RBP
-       movq_cfi  r8,  R8+8-RBP
-       movq_cfi  r9,  R9+8-RBP
-       movq_cfi r10, R10+8-RBP
-       movq_cfi r11, R11+8-RBP
-
-       leaq -RBP+8(%rsp),%rdi  /* arg1 for handler */
-       movq_cfi rbp, 8         /* push %rbp */
-       leaq 8(%rsp), %rbp              /* mov %rsp, %ebp */
+       /* start from rbp in pt_regs and jump over */
+       movq_cfi rdi, RDI-RBP
+       movq_cfi rsi, RSI-RBP
+       movq_cfi rdx, RDX-RBP
+       movq_cfi rcx, RCX-RBP
+       movq_cfi rax, RAX-RBP
+       movq_cfi  r8,  R8-RBP
+       movq_cfi  r9,  R9-RBP
+       movq_cfi r10, R10-RBP
+       movq_cfi r11, R11-RBP
+
+       leaq -RBP(%rsp),%rdi    /* arg1 for handler */
+       movq_cfi rbp, 0         /* push %rbp */
+       movq %rsp, %rbp
        testl $3, CS(%rdi)
        je 1f
        SWAPGS
@@ -329,19 +324,14 @@ ENTRY(save_args)
         */
 1:     incl PER_CPU_VAR(irq_count)
        jne 2f
-       popq_cfi %rax                   /* move return address... */
        mov PER_CPU_VAR(irq_stack_ptr),%rsp
        EMPTY_FRAME 0
        pushq_cfi %rbp                  /* backlink for unwinder */
-       pushq_cfi %rax                  /* ... to the new stack */
        /*
         * We entered an interrupt context - irqs are off:
         */
 2:     TRACE_IRQS_OFF
-       ret
-       CFI_ENDPROC
-END(save_args)
-       .popsection
+       .endm
 
 ENTRY(save_rest)
        PARTIAL_FRAME 1 REST_SKIP+8
@@ -791,7 +781,7 @@ END(interrupt)
        /* reserve pt_regs for scratch regs and rbp */
        subq $ORIG_RAX-RBP, %rsp
        CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP
-       call save_args
+       SAVE_ARGS_IRQ
        PARTIAL_FRAME 0
        call \func
        .endm