x86/head: Add unwind hint annotations

Jiri Slaby reported an ORC issue when unwinding from an idle task.  The
stack was:

    ffffffff811083c2 do_idle+0x142/0x1e0
    ffffffff8110861d cpu_startup_entry+0x5d/0x60
    ffffffff82715f58 start_kernel+0x3ff/0x407
    ffffffff827153e8 x86_64_start_kernel+0x14e/0x15d
    ffffffff810001bf secondary_startup_64+0x9f/0xa0

The ORC unwinder errored out at secondary_startup_64 because the head
code isn't annotated yet so there wasn't a corresponding ORC entry.

Fix that and any other head-related unwinding issues by adding unwind
hints to the head code.

Reported-by: Jiri Slaby <jslaby@suse.cz>
Tested-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/78ef000a2f68f545d6eef44ee912edceaad82ccf.1505764066.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index fd0a7895b63f57bd77a4310936e6d239a45035d1..d8e2b700d1dbe9516e8e73a79f2d61c6175afc71 100644 (file)
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -26,7 +26,6 @@ KASAN_SANITIZE_dumpstack.o                            := n
 KASAN_SANITIZE_dumpstack_$(BITS).o                     := n
 KASAN_SANITIZE_stacktrace.o := n
 
-OBJECT_FILES_NON_STANDARD_head_$(BITS).o               := y
 OBJECT_FILES_NON_STANDARD_relocate_kernel_$(BITS).o    := y
 OBJECT_FILES_NON_STANDARD_ftrace_$(BITS).o             := y
 OBJECT_FILES_NON_STANDARD_test_nx.o                    := y

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index edacd579d5047ee8479104bc255a7a6b3ac606e8..42e32c2e51bb5f5125db9032de3b343e37ec5100 100644 (file)
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -49,6 +49,7 @@ L3_START_KERNEL = pud_index(__START_KERNEL_map)
        .code64
        .globl startup_64
 startup_64:
+       UNWIND_HINT_EMPTY
        /*
         * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
         * and someone has loaded an identity mapped page table
@@ -88,6 +89,7 @@ startup_64:
        addq    $(early_top_pgt - __START_KERNEL_map), %rax
        jmp 1f
 ENTRY(secondary_startup_64)
+       UNWIND_HINT_EMPTY
        /*
         * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
         * and someone has loaded a mapped page table.
@@ -132,6 +134,7 @@ ENTRY(secondary_startup_64)
        movq    $1f, %rax
        jmp     *%rax
 1:
+       UNWIND_HINT_EMPTY
 
        /* Check if nx is implemented */
        movl    $0x80000001, %eax
@@ -246,6 +249,7 @@ END(secondary_startup_64)
  */
 ENTRY(start_cpu0)
        movq    initial_stack(%rip), %rsp
+       UNWIND_HINT_EMPTY
        jmp     .Ljump_to_C_code
 ENDPROC(start_cpu0)
 #endif
@@ -270,13 +274,18 @@ ENTRY(early_idt_handler_array)
        i = 0
        .rept NUM_EXCEPTION_VECTORS
        .ifeq (EXCEPTION_ERRCODE_MASK >> i) & 1
-       pushq $0                # Dummy error code, to make stack frame uniform
+               UNWIND_HINT_IRET_REGS
+               pushq $0        # Dummy error code, to make stack frame uniform
+       .else
+               UNWIND_HINT_IRET_REGS offset=8
        .endif
        pushq $i                # 72(%rsp) Vector number
        jmp early_idt_handler_common
+       UNWIND_HINT_IRET_REGS
        i = i + 1
        .fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
        .endr
+       UNWIND_HINT_IRET_REGS offset=16
 END(early_idt_handler_array)
 
 early_idt_handler_common:
@@ -305,6 +314,7 @@ early_idt_handler_common:
        pushq %r13                              /* pt_regs->r13 */
        pushq %r14                              /* pt_regs->r14 */
        pushq %r15                              /* pt_regs->r15 */
+       UNWIND_HINT_REGS
 
        cmpq $14,%rsi           /* Page fault? */
        jnz 10f
@@ -427,7 +437,7 @@ ENTRY(phys_base)
 EXPORT_SYMBOL(phys_base)
 
 #include "../../x86/xen/xen-head.S"
-       
+
        __PAGE_ALIGNED_BSS
 NEXT_PAGE(empty_zero_page)
        .skip PAGE_SIZE