Commit 1c3e5d3f authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
Browse files

x86/entry: Make entry_64_compat.S objtool clean 



Currently entry_64_compat is exempt from objtool, but with vmlinux
mode there is no hiding it.

Make the following changes to make it pass:

 - change entry_SYSENTER_compat to STT_NOTYPE; it's not a function
   and doesn't have function type stack setup.

 - mark all STT_NOTYPE symbols with UNWIND_HINT_EMPTY; so we do
   validate them and don't treat them as unreachable.

 - don't abuse RSP as a temp register, this confuses objtool
   mightily as it (rightfully) thinks we're doing unspeakable
   things to the stack.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: default avatarAndy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505134341.272248024@linutronix.de
parent a7ef9ba9

arch/x86/entry/Makefile

+0 −2
Original line number Diff line number Diff line
@@ -11,8 +11,6 @@ CFLAGS_REMOVE_common.o = $(CC_FLAGS_FTRACE) -fstack-protector -fstack-protector- 
CFLAGS_REMOVE_syscall_32.o = $(CC_FLAGS_FTRACE) -fstack-protector -fstack-protector-strong

CFLAGS_REMOVE_syscall_64.o = $(CC_FLAGS_FTRACE) -fstack-protector -fstack-protector-strong



OBJECT_FILES_NON_STANDARD_entry_64_compat.o := y



CFLAGS_syscall_64.o		+= $(call cc-option,-Wno-override-init,)

CFLAGS_syscall_32.o		+= $(call cc-option,-Wno-override-init,)

obj-y				:= entry_$(BITS).o thunk_$(BITS).o syscall_$(BITS).o

arch/x86/entry/entry_64_compat.S

+20 −5
Original line number Diff line number Diff line
@@ -46,12 +46,14 @@ 
 * ebp  user stack

 * 0(%ebp) arg6

 */

SYM_FUNC_START(entry_SYSENTER_compat)

SYM_CODE_START(entry_SYSENTER_compat)

	UNWIND_HINT_EMPTY

	/* Interrupts are off on entry. */

	SWAPGS



	/* We are about to clobber %rsp anyway, clobbering here is OK */

	SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp

	pushq	%rax

	SWITCH_TO_KERNEL_CR3 scratch_reg=%rax

	popq	%rax



	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp
@@ -104,6 +106,9 @@ SYM_FUNC_START(entry_SYSENTER_compat) 
	xorl	%r14d, %r14d		/* nospec   r14 */

	pushq   $0			/* pt_regs->r15 = 0 */

	xorl	%r15d, %r15d		/* nospec   r15 */



	UNWIND_HINT_REGS



	cld



	/*
@@ -141,7 +146,7 @@ SYM_FUNC_START(entry_SYSENTER_compat) 
	popfq

	jmp	.Lsysenter_flags_fixed

SYM_INNER_LABEL(__end_entry_SYSENTER_compat, SYM_L_GLOBAL)

SYM_FUNC_END(entry_SYSENTER_compat)

SYM_CODE_END(entry_SYSENTER_compat)



/*

 * 32-bit SYSCALL entry.
@@ -191,6 +196,7 @@ SYM_FUNC_END(entry_SYSENTER_compat) 
 * 0(%esp) arg6

 */

SYM_CODE_START(entry_SYSCALL_compat)

	UNWIND_HINT_EMPTY

	/* Interrupts are off on entry. */

	swapgs
@@ -241,6 +247,8 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_after_hwframe, SYM_L_GLOBAL) 
	pushq   $0			/* pt_regs->r15 = 0 */

	xorl	%r15d, %r15d		/* nospec   r15 */



	UNWIND_HINT_REGS



	movq	%rsp, %rdi

	call	do_fast_syscall_32

	/* XEN PV guests always use IRET path */
@@ -328,6 +336,7 @@ SYM_CODE_END(entry_SYSCALL_compat) 
 * ebp  arg6

 */

SYM_CODE_START(entry_INT80_compat)

	UNWIND_HINT_EMPTY

	/*

	 * Interrupts are off on entry.

	 */
@@ -349,8 +358,11 @@ SYM_CODE_START(entry_INT80_compat) 


	/* Need to switch before accessing the thread stack. */

	SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi



	/* In the Xen PV case we already run on the thread stack. */

	ALTERNATIVE "movq %rsp, %rdi", "jmp .Lint80_keep_stack", X86_FEATURE_XENPV

	ALTERNATIVE "", "jmp .Lint80_keep_stack", X86_FEATURE_XENPV



	movq	%rsp, %rdi

	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp



	pushq	6*8(%rdi)		/* regs->ss */
@@ -389,6 +401,9 @@ SYM_CODE_START(entry_INT80_compat) 
	xorl	%r14d, %r14d		/* nospec   r14 */

	pushq   %r15                    /* pt_regs->r15 */

	xorl	%r15d, %r15d		/* nospec   r15 */



	UNWIND_HINT_REGS



	cld



	movq	%rsp, %rdi

CRA Git | Maintained and supported by SUSTech CRA and CCSE