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Subject[patch V3 10/23] x86/entry: Move irq tracing on syscall entry to C-code
Now that the C entry points are safe, move the irq flags tracing code into
the entry helper:

- Invoke lockdep before calling into context tracking

- Use the safe __trace_hardirqs_on() trace function after context
tracking established state and RCU is watching.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/entry/common.c | 21 +++++++++++++++++++--
arch/x86/entry/entry_32.S | 12 ------------
arch/x86/entry/entry_64.S | 2 --
arch/x86/entry/entry_64_compat.S | 18 ------------------
4 files changed, 19 insertions(+), 34 deletions(-)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -39,19 +39,36 @@
#include <trace/events/syscalls.h>

#ifdef CONFIG_CONTEXT_TRACKING
-/* Called on entry from user mode with IRQs off. */
+/**
+ * enter_from_user_mode - Establish state when coming from user mode
+ *
+ * Syscall entry disables interrupts, but user mode is traced as interrupts
+ * enabled. Also with NO_HZ_FULL RCU might be idle.
+ *
+ * 1) Tell lockdep that interrupts are disabled
+ * 2) Invoke context tracking if enabled to reactivate RCU
+ * 3) Trace interrupts off state
+ */
__visible noinstr void enter_from_user_mode(void)
{
enum ctx_state state = ct_state();

+ lockdep_hardirqs_off(CALLER_ADDR0);
user_exit_irqoff();

instr_begin();
CT_WARN_ON(state != CONTEXT_USER);
+ __trace_hardirqs_off();
instr_end();
}
#else
-static inline void enter_from_user_mode(void) {}
+static __always_inline void enter_from_user_mode(void)
+{
+ lockdep_hardirqs_off(CALLER_ADDR0);
+ instr_begin();
+ __trace_hardirqs_off();
+ instr_end();
+}
#endif

static __always_inline void exit_to_user_mode(void)
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -960,12 +960,6 @@ SYM_FUNC_START(entry_SYSENTER_32)
jnz .Lsysenter_fix_flags
.Lsysenter_flags_fixed:

- /*
- * User mode is traced as though IRQs are on, and SYSENTER
- * turned them off.
- */
- TRACE_IRQS_OFF
-
movl %esp, %eax
call do_fast_syscall_32
/* XEN PV guests always use IRET path */
@@ -1075,12 +1069,6 @@ SYM_FUNC_START(entry_INT80_32)

SAVE_ALL pt_regs_ax=$-ENOSYS switch_stacks=1 /* save rest */

- /*
- * User mode is traced as though IRQs are on, and the interrupt gate
- * turned them off.
- */
- TRACE_IRQS_OFF
-
movl %esp, %eax
call do_int80_syscall_32
.Lsyscall_32_done:
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -167,8 +167,6 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_h

PUSH_AND_CLEAR_REGS rax=$-ENOSYS

- TRACE_IRQS_OFF
-
/* IRQs are off. */
movq %rax, %rdi
movq %rsp, %rsi
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -129,12 +129,6 @@ SYM_FUNC_START(entry_SYSENTER_compat)
jnz .Lsysenter_fix_flags
.Lsysenter_flags_fixed:

- /*
- * User mode is traced as though IRQs are on, and SYSENTER
- * turned them off.
- */
- TRACE_IRQS_OFF
-
movq %rsp, %rdi
call do_fast_syscall_32
/* XEN PV guests always use IRET path */
@@ -247,12 +241,6 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_aft
pushq $0 /* pt_regs->r15 = 0 */
xorl %r15d, %r15d /* nospec r15 */

- /*
- * User mode is traced as though IRQs are on, and SYSENTER
- * turned them off.
- */
- TRACE_IRQS_OFF
-
movq %rsp, %rdi
call do_fast_syscall_32
/* XEN PV guests always use IRET path */
@@ -403,12 +391,6 @@ SYM_CODE_START(entry_INT80_compat)
xorl %r15d, %r15d /* nospec r15 */
cld

- /*
- * User mode is traced as though IRQs are on, and the interrupt
- * gate turned them off.
- */
- TRACE_IRQS_OFF
-
movq %rsp, %rdi
call do_int80_syscall_32
.Lsyscall_32_done:
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