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x86/entry: Move irq flags tracing to prepare_exit_to_usermode()

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This is another step towards more C-code and less convoluted ASM.

Similar to the entry path, invoke the tracer before context tracking which
might turn off RCU and invoke lockdep as the last step before going back to
user space. Annotate the code sections in exit_to_user_mode() accordingly
so objtool won't complain about the tracer invocation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505134340.703783926@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-03-04 12:51:59 +01:00
parent dd8e2d9ae6
commit 4983e5d74c
4 changed files with 27 additions and 22 deletions
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19
arch/x86/entry/common.c
View File

@ -72,10 +72,27 @@ static __always_inline void enter_from_user_mode(void)
}
#endif
static noinstr void exit_to_user_mode(void)
/**
* exit_to_user_mode - Fixup state when exiting to user mode
*
* Syscall exit enables interrupts, but the kernel state is interrupts
* disabled when this is invoked. Also tell RCU about it.
*
* 1) Trace interrupts on state
* 2) Invoke context tracking if enabled to adjust RCU state
* 3) Clear CPU buffers if CPU is affected by MDS and the migitation is on.
* 4) Tell lockdep that interrupts are enabled
*/
static __always_inline void exit_to_user_mode(void)
{
instrumentation_begin();
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare(CALLER_ADDR0);
instrumentation_end();
user_enter_irqoff();
mds_user_clear_cpu_buffers();
lockdep_hardirqs_on(CALLER_ADDR0);
}
static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)

10
arch/x86/entry/entry_32.S
View File

@ -817,8 +817,7 @@ SYM_CODE_START(ret_from_fork)
/* When we fork, we trace the syscall return in the child, too. */
movl %esp, %eax
call syscall_return_slowpath
STACKLEAK_ERASE
jmp restore_all
jmp .Lsyscall_32_done
/* kernel thread */
1: movl %edi, %eax
@ -862,7 +861,7 @@ ret_from_intr:
TRACE_IRQS_OFF
movl %esp, %eax
call prepare_exit_to_usermode
jmp restore_all
jmp restore_all_switch_stack
SYM_CODE_END(ret_from_exception)
SYM_ENTRY(__begin_SYSENTER_singlestep_region, SYM_L_GLOBAL, SYM_A_NONE)
@ -976,7 +975,6 @@ SYM_FUNC_START(entry_SYSENTER_32)
STACKLEAK_ERASE
/* Opportunistic SYSEXIT */
TRACE_IRQS_ON /* User mode traces as IRQs on. */
/*
* Setup entry stack - we keep the pointer in %eax and do the
@ -1079,11 +1077,9 @@ SYM_FUNC_START(entry_INT80_32)
movl %esp, %eax
call do_int80_syscall_32
.Lsyscall_32_done:
STACKLEAK_ERASE
restore_all:
TRACE_IRQS_ON
restore_all_switch_stack:
SWITCH_TO_ENTRY_STACK
CHECK_AND_APPLY_ESPFIX

4
arch/x86/entry/entry_64.S
View File

@ -172,8 +172,6 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe, SYM_L_GLOBAL)
movq %rsp, %rsi
call do_syscall_64 /* returns with IRQs disabled */
TRACE_IRQS_ON /* return enables interrupts */
/*
* Try to use SYSRET instead of IRET if we're returning to
* a completely clean 64-bit userspace context. If we're not,
@ -342,7 +340,6 @@ SYM_CODE_START(ret_from_fork)
UNWIND_HINT_REGS
movq %rsp, %rdi
call syscall_return_slowpath /* returns with IRQs disabled */
TRACE_IRQS_ON /* user mode is traced as IRQS on */
jmp swapgs_restore_regs_and_return_to_usermode
1:
@ -620,7 +617,6 @@ ret_from_intr:
.Lretint_user:
mov %rsp,%rdi
call prepare_exit_to_usermode
TRACE_IRQS_ON
SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL)
#ifdef CONFIG_DEBUG_ENTRY

14
arch/x86/entry/entry_64_compat.S
View File

@ -132,8 +132,8 @@ SYM_FUNC_START(entry_SYSENTER_compat)
movq %rsp, %rdi
call do_fast_syscall_32
/* XEN PV guests always use IRET path */
ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
"jmp .Lsyscall_32_done", X86_FEATURE_XENPV
ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \
"jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV
jmp sysret32_from_system_call
.Lsysenter_fix_flags:
@ -244,8 +244,8 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_after_hwframe, SYM_L_GLOBAL)
movq %rsp, %rdi
call do_fast_syscall_32
/* XEN PV guests always use IRET path */
ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
"jmp .Lsyscall_32_done", X86_FEATURE_XENPV
ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \
"jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV
/* Opportunistic SYSRET */
sysret32_from_system_call:
@ -254,7 +254,7 @@ sysret32_from_system_call:
* stack. So let's erase the thread stack right now.
*/
STACKLEAK_ERASE
TRACE_IRQS_ON /* User mode traces as IRQs on. */
movq RBX(%rsp), %rbx /* pt_regs->rbx */
movq RBP(%rsp), %rbp /* pt_regs->rbp */
movq EFLAGS(%rsp), %r11 /* pt_regs->flags (in r11) */
@ -393,9 +393,5 @@ SYM_CODE_START(entry_INT80_compat)
movq %rsp, %rdi
call do_int80_syscall_32
.Lsyscall_32_done:
/* Go back to user mode. */
TRACE_IRQS_ON
jmp swapgs_restore_regs_and_return_to_usermode
SYM_CODE_END(entry_INT80_compat)