---

yaml
---
r: 21023
b: refs/heads/master
c: c33d456
h: refs/heads/master
i:
  21021: a90b57e
  21019: c4021e5
  21015: a8f361f
  21007: 17f8c3f
  20991: d2687a6
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 31fe4d331729e9687db84521c3ceb8e43390efcf
+refs/heads/master: c33d4568aca9028a22857f94f5e0850012b6444b

trunk/arch/x86_64/kernel/entry.S

@@ -178,6 +178,12 @@ rff_trace:
  * Interrupts are off on entry.
  * Only called from user space.
  *
+ * EM64T CPUs have somewhat weird error reporting for non canonical RIPs in SYSRET. 
+ * We can't handle any exceptions there because the exception handler would
+ * end up running on the user stack which is unsafe. To avoid problems 
+ * any code that might end up with a user touched pt_regs should return
+ * using int_ret_from_syscall.
+ *
  * XXX	if we had a free scratch register we could save the RSP into the stack frame
  *      and report it properly in ps. Unfortunately we haven't.
  */ 			 		
@@ -254,7 +260,9 @@ sysret_signal:
 	xorl %esi,%esi # oldset -> arg2
 	call ptregscall_common
 1:	movl $_TIF_NEED_RESCHED,%edi
-	jmp sysret_check
+	/* Stack frame might have been changed. The IRET path does
+	   some additional checks to handle this */
+	jmp int_with_check
 
 badsys:
 	movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
@@ -280,7 +288,8 @@ tracesys:
 	call syscall_trace_leave
 	RESTORE_TOP_OF_STACK %rbx
 	RESTORE_REST
-	jmp ret_from_sys_call
+	/* Stack frame might have been changed. Use the more careful IRET path */
+	jmp int_ret_from_sys_call
 	CFI_ENDPROC
 
 /* 
@@ -408,25 +417,9 @@ ENTRY(stub_execve)
 	CFI_ADJUST_CFA_OFFSET -8
 	CFI_REGISTER rip, r11
 	SAVE_REST
-	movq %r11, %r15
-	CFI_REGISTER rip, r15
 	FIXUP_TOP_OF_STACK %r11
 	call sys_execve
-	GET_THREAD_INFO(%rcx)
-	bt $TIF_IA32,threadinfo_flags(%rcx)
-	CFI_REMEMBER_STATE
-	jc exec_32bit
 	RESTORE_TOP_OF_STACK %r11
-	movq %r15, %r11
-	CFI_REGISTER rip, r11
-	RESTORE_REST
-	pushq %r11
-	CFI_ADJUST_CFA_OFFSET 8
-	CFI_REL_OFFSET rip, 0
-	ret
-
-exec_32bit:
-	CFI_RESTORE_STATE
 	movq %rax,RAX(%rsp)
 	RESTORE_REST
 	jmp int_ret_from_sys_call