linux-kernel - [PATCH 5.10 009/148] x86/xen: Support objtool validation in xen-asm.S

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Date:   Sat, 23 Jul 2022 11:53:41 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Ben Hutchings <ben@...adent.org.uk>
Subject: [PATCH 5.10 009/148] x86/xen: Support objtool validation in xen-asm.S

From: Josh Poimboeuf <jpoimboe@...hat.com>

commit cde07a4e4434ddfb9b1616ac971edf6d66329804 upstream.

The OBJECT_FILES_NON_STANDARD annotation is used to tell objtool to
ignore a file.  File-level ignores won't work when validating vmlinux.o.

Tweak the ELF metadata and unwind hints to allow objtool to follow the
code.

Cc: Juergen Gross <jgross@...e.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Link: https://lore.kernel.org/r/8b042a09c69e8645f3b133ef6653ba28f896807d.1611263462.git.jpoimboe@redhat.com
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/xen/Makefile  |    1 -
 arch/x86/xen/xen-asm.S |   29 +++++++++++++++++++----------
 2 files changed, 19 insertions(+), 11 deletions(-)

--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -1,5 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
-OBJECT_FILES_NON_STANDARD_xen-asm.o := y
 
 ifdef CONFIG_FUNCTION_TRACER
 # Do not profile debug and lowlevel utilities
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -14,6 +14,7 @@
 #include <asm/thread_info.h>
 #include <asm/asm.h>
 #include <asm/frame.h>
+#include <asm/unwind_hints.h>
 
 #include <xen/interface/xen.h>
 
@@ -147,6 +148,7 @@ SYM_FUNC_END(xen_read_cr2_direct);
 
 .macro xen_pv_trap name
 SYM_CODE_START(xen_\name)
+	UNWIND_HINT_EMPTY
 	pop %rcx
 	pop %r11
 	jmp  \name
@@ -186,6 +188,7 @@ xen_pv_trap asm_exc_xen_hypervisor_callb
 SYM_CODE_START(xen_early_idt_handler_array)
 	i = 0
 	.rept NUM_EXCEPTION_VECTORS
+	UNWIND_HINT_EMPTY
 	pop %rcx
 	pop %r11
 	jmp early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE
@@ -212,11 +215,13 @@ hypercall_iret = hypercall_page + __HYPE
  * rsp->rax		}
  */
 SYM_CODE_START(xen_iret)
+	UNWIND_HINT_EMPTY
 	pushq $0
 	jmp hypercall_iret
 SYM_CODE_END(xen_iret)
 
 SYM_CODE_START(xen_sysret64)
+	UNWIND_HINT_EMPTY
 	/*
 	 * We're already on the usermode stack at this point, but
 	 * still with the kernel gs, so we can easily switch back.
@@ -271,7 +276,8 @@ SYM_CODE_END(xenpv_restore_regs_and_retu
  */
 
 /* Normal 64-bit system call target */
-SYM_FUNC_START(xen_syscall_target)
+SYM_CODE_START(xen_syscall_target)
+	UNWIND_HINT_EMPTY
 	popq %rcx
 	popq %r11
 
@@ -284,12 +290,13 @@ SYM_FUNC_START(xen_syscall_target)
 	movq $__USER_CS, 1*8(%rsp)
 
 	jmp entry_SYSCALL_64_after_hwframe
-SYM_FUNC_END(xen_syscall_target)
+SYM_CODE_END(xen_syscall_target)
 
 #ifdef CONFIG_IA32_EMULATION
 
 /* 32-bit compat syscall target */
-SYM_FUNC_START(xen_syscall32_target)
+SYM_CODE_START(xen_syscall32_target)
+	UNWIND_HINT_EMPTY
 	popq %rcx
 	popq %r11
 
@@ -302,10 +309,11 @@ SYM_FUNC_START(xen_syscall32_target)
 	movq $__USER32_CS, 1*8(%rsp)
 
 	jmp entry_SYSCALL_compat_after_hwframe
-SYM_FUNC_END(xen_syscall32_target)
+SYM_CODE_END(xen_syscall32_target)
 
 /* 32-bit compat sysenter target */
-SYM_FUNC_START(xen_sysenter_target)
+SYM_CODE_START(xen_sysenter_target)
+	UNWIND_HINT_EMPTY
 	/*
 	 * NB: Xen is polite and clears TF from EFLAGS for us.  This means
 	 * that we don't need to guard against single step exceptions here.
@@ -322,17 +330,18 @@ SYM_FUNC_START(xen_sysenter_target)
 	movq $__USER32_CS, 1*8(%rsp)
 
 	jmp entry_SYSENTER_compat_after_hwframe
-SYM_FUNC_END(xen_sysenter_target)
+SYM_CODE_END(xen_sysenter_target)
 
 #else /* !CONFIG_IA32_EMULATION */
 
-SYM_FUNC_START_ALIAS(xen_syscall32_target)
-SYM_FUNC_START(xen_sysenter_target)
+SYM_CODE_START(xen_syscall32_target)
+SYM_CODE_START(xen_sysenter_target)
+	UNWIND_HINT_EMPTY
 	lea 16(%rsp), %rsp	/* strip %rcx, %r11 */
 	mov $-ENOSYS, %rax
 	pushq $0
 	jmp hypercall_iret
-SYM_FUNC_END(xen_sysenter_target)
-SYM_FUNC_END_ALIAS(xen_syscall32_target)
+SYM_CODE_END(xen_sysenter_target)
+SYM_CODE_END(xen_syscall32_target)
 
 #endif	/* CONFIG_IA32_EMULATION */