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-rw-r--r--arch/x86/kernel/entry_64.S31
1 files changed, 16 insertions, 15 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index e41734a537b..3194636a429 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -361,34 +361,35 @@ ENTRY(save_paranoid)
END(save_paranoid)
/*
- * A newly forked process directly context switches into this.
+ * A newly forked process directly context switches into this address.
+ *
+ * rdi: prev task we switched from
*/
-/* rdi: prev */
ENTRY(ret_from_fork)
DEFAULT_FRAME
+
push kernel_eflags(%rip)
CFI_ADJUST_CFA_OFFSET 8
- popf # reset kernel eflags
+ popf # reset kernel eflags
CFI_ADJUST_CFA_OFFSET -8
- call schedule_tail
+
+ call schedule_tail # rdi: 'prev' task parameter
+
GET_THREAD_INFO(%rcx)
- testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),TI_flags(%rcx)
+
CFI_REMEMBER_STATE
- jnz rff_trace
-rff_action:
RESTORE_REST
- testl $3,CS-ARGOFFSET(%rsp) # from kernel_thread?
+
+ testl $3, CS-ARGOFFSET(%rsp) # from kernel_thread?
je int_ret_from_sys_call
- testl $_TIF_IA32,TI_flags(%rcx)
+
+ testl $_TIF_IA32, TI_flags(%rcx) # 32-bit compat task needs IRET
jnz int_ret_from_sys_call
+
RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
- jmp ret_from_sys_call
+ jmp ret_from_sys_call # go to the SYSRET fastpath
+
CFI_RESTORE_STATE
-rff_trace:
- movq %rsp,%rdi
- call syscall_trace_leave
- GET_THREAD_INFO(%rcx)
- jmp rff_action
CFI_ENDPROC
END(ret_from_fork)