Commit 2704fbb6 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

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: default avatarJiri Slaby <jslaby@suse.cz>
Tested-by: default avatarJiri Slaby <jslaby@suse.cz>
Signed-off-by: default avatarJosh 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: default avatarIngo Molnar <mingo@kernel.org>
parent abbe1cac

arch/x86/kernel/Makefile

+0 −1
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/head_64.S

+12 −2
Original line number Diff line number Diff line
@@ -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

		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

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