[PATCH 5.10 009/130] x86/xen: Support objtool validation in xen-asm.S

Greg Kroah-Hartman
2022-07-12T18:42:16Z

From: Josh Poimboeuf <jpoimboe@redhat.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@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/8b042a09c69e8645f3b133ef6653ba28f896807d.1611263462.git.jpoimboe@redhat.com
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 */