x86-64: Fix CFI data for interrupt frames

The patch titled "x86: Don't use frame pointer to save old stack
on irq entry" did not properly adjust CFI directives, so this
patch is a follow-up to that one.

With the old stack pointer no longer stored in a callee-saved
register (plus some offset), we now have to use a CFA expression
to describe the memory location where it is being found. This
requires the use of .cfi_escape (allowing arbitrary byte streams
to be emitted into .eh_frame), as there is no
.cfi_def_cfa_expression (which also cannot reasonably be
expected, as it would require a full expression parser).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/4E8360200200007800058467@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 11 insertions, 5 deletions

diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
index 326099199318..f6f15986df6c 100644
--- a/arch/x86/include/asm/dwarf2.h
+++ b/arch/x86/include/asm/dwarf2.h
@@ -27,6 +27,7 @@
 #define CFI_REMEMBER_STATE      .cfi_remember_state
 #define CFI_RESTORE_STATE       .cfi_restore_state
 #define CFI_UNDEFINED           .cfi_undefined
+#define CFI_ESCAPE              .cfi_escape
 
 #ifdef CONFIG_AS_CFI_SIGNAL_FRAME
 #define CFI_SIGNAL_FRAME        .cfi_signal_frame
@@ -68,6 +69,7 @@
 #define CFI_REMEMBER_STATE      cfi_ignore
 #define CFI_RESTORE_STATE       cfi_ignore
 #define CFI_UNDEFINED           cfi_ignore
+#define CFI_ESCAPE              cfi_ignore
 #define CFI_SIGNAL_FRAME        cfi_ignore
 
 #endif
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 6419bb05ecd5..faf8d5e74b0b 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -331,10 +331,15 @@ ENDPROC(native_usergs_sysret64)
 1:      incl PER_CPU_VAR(irq_count)
         jne 2f
         mov PER_CPU_VAR(irq_stack_ptr),%rsp
-        EMPTY_FRAME 0
+        CFI_DEF_CFA_REGISTER    rsi
 
 2:      /* Store previous stack value */
         pushq %rsi
+        CFI_ESCAPE      0x0f /* DW_CFA_def_cfa_expression */, 6, \
+                        0x77 /* DW_OP_breg7 */, 0, \
+                        0x06 /* DW_OP_deref */, \
+                        0x08 /* DW_OP_const1u */, SS+8-RBP, \
+                        0x22 /* DW_OP_plus */
         /* We entered an interrupt context - irqs are off: */
         TRACE_IRQS_OFF
         .endm
@@ -788,7 +793,6 @@ END(interrupt)
         subq $ORIG_RAX-RBP, %rsp
         CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP
         SAVE_ARGS_IRQ
-        PARTIAL_FRAME 0
         call \func
         .endm
 
@@ -813,10 +817,10 @@ ret_from_intr:
 
         /* Restore saved previous stack */
         popq %rsi
-        leaq 16(%rsi), %rsp
-
+        CFI_DEF_CFA_REGISTER    rsi
+        leaq ARGOFFSET-RBP(%rsi), %rsp
         CFI_DEF_CFA_REGISTER    rsp
-        CFI_ADJUST_CFA_OFFSET   -16
+        CFI_ADJUST_CFA_OFFSET   RBP-ARGOFFSET
 
 exit_intr:
         GET_THREAD_INFO(%rcx)