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Subject[tip: objtool/core] x86/xen: Make save_fl() noinstr
The following commit has been merged into the objtool/core branch of tip:

Commit-ID: 1126696d60d04b844be88db50099f8fdb43d8166
Gitweb: https://git.kernel.org/tip/1126696d60d04b844be88db50099f8fdb43d8166
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 24 Jun 2021 11:41:17 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 15 Sep 2021 15:51:49 +02:00

x86/xen: Make save_fl() noinstr

vmlinux.o: warning: objtool: pv_ops[30]: native_save_fl
vmlinux.o: warning: objtool: pv_ops[30]: __raw_callee_save_xen_save_fl
vmlinux.o: warning: objtool: pv_ops[30]: xen_save_fl_direct
vmlinux.o: warning: objtool: lockdep_hardirqs_off()+0x73: call to pv_ops[30]() leaves .noinstr.text section

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20210624095148.749712274@infradead.org
---
arch/x86/include/asm/paravirt.h | 7 +++++--
arch/x86/kernel/irqflags.S | 2 ++-
arch/x86/xen/irq.c | 4 ++--
arch/x86/xen/xen-asm.S | 32 ++++++++++++++++----------------
4 files changed, 25 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 34da790..cebec95 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -653,10 +653,10 @@ bool __raw_callee_save___native_vcpu_is_preempted(long cpu);
* functions.
*/
#define PV_THUNK_NAME(func) "__raw_callee_save_" #func
-#define PV_CALLEE_SAVE_REGS_THUNK(func) \
+#define __PV_CALLEE_SAVE_REGS_THUNK(func, section) \
extern typeof(func) __raw_callee_save_##func; \
\
- asm(".pushsection .text;" \
+ asm(".pushsection " section ", \"ax\";" \
".globl " PV_THUNK_NAME(func) ";" \
".type " PV_THUNK_NAME(func) ", @function;" \
PV_THUNK_NAME(func) ":" \
@@ -669,6 +669,9 @@ bool __raw_callee_save___native_vcpu_is_preempted(long cpu);
".size " PV_THUNK_NAME(func) ", .-" PV_THUNK_NAME(func) ";" \
".popsection")

+#define PV_CALLEE_SAVE_REGS_THUNK(func) \
+ __PV_CALLEE_SAVE_REGS_THUNK(func, ".text")
+
/* Get a reference to a callee-save function */
#define PV_CALLEE_SAVE(func) \
((struct paravirt_callee_save) { __raw_callee_save_##func })
diff --git a/arch/x86/kernel/irqflags.S b/arch/x86/kernel/irqflags.S
index 8ef3506..760e1f2 100644
--- a/arch/x86/kernel/irqflags.S
+++ b/arch/x86/kernel/irqflags.S
@@ -7,9 +7,11 @@
/*
* unsigned long native_save_fl(void)
*/
+.pushsection .noinstr.text, "ax"
SYM_FUNC_START(native_save_fl)
pushf
pop %_ASM_AX
ret
SYM_FUNC_END(native_save_fl)
+.popsection
EXPORT_SYMBOL(native_save_fl)
diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
index dfa091d..9c71f43 100644
--- a/arch/x86/xen/irq.c
+++ b/arch/x86/xen/irq.c
@@ -24,7 +24,7 @@ void xen_force_evtchn_callback(void)
(void)HYPERVISOR_xen_version(0, NULL);
}

-asmlinkage __visible unsigned long xen_save_fl(void)
+asmlinkage __visible noinstr unsigned long xen_save_fl(void)
{
struct vcpu_info *vcpu;
unsigned long flags;
@@ -40,7 +40,7 @@ asmlinkage __visible unsigned long xen_save_fl(void)
*/
return (-flags) & X86_EFLAGS_IF;
}
-PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
+__PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl, ".noinstr.text");

asmlinkage __visible void xen_irq_disable(void)
{
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index aef4a1e..0883e39 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -58,22 +58,6 @@ SYM_FUNC_START(xen_irq_disable_direct)
SYM_FUNC_END(xen_irq_disable_direct)

/*
- * (xen_)save_fl is used to get the current interrupt enable status.
- * Callers expect the status to be in X86_EFLAGS_IF, and other bits
- * may be set in the return value. We take advantage of this by
- * making sure that X86_EFLAGS_IF has the right value (and other bits
- * in that byte are 0), but other bits in the return value are
- * undefined. We need to toggle the state of the bit, because Xen and
- * x86 use opposite senses (mask vs enable).
- */
-SYM_FUNC_START(xen_save_fl_direct)
- testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
- setz %ah
- addb %ah, %ah
- ret
-SYM_FUNC_END(xen_save_fl_direct)
-
-/*
* Force an event check by making a hypercall, but preserve regs
* before making the call.
*/
@@ -103,6 +87,22 @@ SYM_FUNC_START(check_events)
SYM_FUNC_END(check_events)

.pushsection .noinstr.text, "ax"
+/*
+ * (xen_)save_fl is used to get the current interrupt enable status.
+ * Callers expect the status to be in X86_EFLAGS_IF, and other bits
+ * may be set in the return value. We take advantage of this by
+ * making sure that X86_EFLAGS_IF has the right value (and other bits
+ * in that byte are 0), but other bits in the return value are
+ * undefined. We need to toggle the state of the bit, because Xen and
+ * x86 use opposite senses (mask vs enable).
+ */
+SYM_FUNC_START(xen_save_fl_direct)
+ testb $0xff, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
+ setz %ah
+ addb %ah, %ah
+ ret
+SYM_FUNC_END(xen_save_fl_direct)
+
SYM_FUNC_START(xen_read_cr2)
FRAME_BEGIN
_ASM_MOV PER_CPU_VAR(xen_vcpu), %_ASM_AX
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