[LV-kern-commit] CVS: kernel-2.4/arch/vax/kernel entry.S,1.2,1.3

[Kenn H. <ke...@us...>]

Update of /cvsroot/linux-vax/kernel-2.4/arch/vax/kernel
In directory usw-pr-cvs1:/tmp/cvs-serv27409

Modified Files:
	entry.S 
Log Message:
Ensure that the pt_regs structure created when an interrupt occurs 
contains the correct stack pointer for the previous mode (rather than
always being the user SP - makes stack dumps more useful)


Index: entry.S
===================================================================
RCS file: /cvsroot/linux-vax/kernel-2.4/arch/vax/kernel/entry.S,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- entry.S	2001/01/26 00:27:00	1.2
+++ entry.S	2001/01/29 00:55:04	1.3
@@ -60,7 +60,26 @@
 
 	pushl (sp)[r0]     /* Push saved PSL again */
 	pushl (sp)[r0]     /* Push saved PC again */
-	mfpr $PR_USP,-(sp) /* Save user SP at time of exception */
+	extzv $22, $2, 4(sp), -(sp)  /* Extract PREVMODE field from saved
+				        PSL and save on stack (because we
+				        don't have any spare registers yet) */
+	cmpzv $24, $2, 8(sp), (sp)   /* Is PREVMODE == CURMODE? */
+	beql same_mode
+	mfpr (sp),(sp)	   /* HACK ALERT!  The processor modes are 0..3
+                              for kernel..user mode.  The stack pointer
+                              internal processor registers are also 0..3
+                              for kernel..user mode.  So, using the 
+                              PREVMODE value we just saved on the stack,
+                              we overwrite it with the correct stack 
+                              pointer register.  Net result:  the saved_sp
+                              here is the correct stack pointer for the
+                              processor mode before the exception occurred */
+	brb sp_saved
+same_mode:
+	moval 16(sp)[r0],(sp) /* Exception is not changing modes.  Therefore
+				 we calculate how far up the stack the SP
+				 was pointing when the exception occurred. */
+sp_saved:
 	pushr $0x3ffe      /* Push FP to R1 */
         pushl 64(sp)       /* Duplicate saved R0 */
 
@@ -69,7 +88,7 @@
            SP:    saved R0
              +4   saved R1
                   ...
-             +56  saved user SP
+             +56  saved SP for previous mode
              +60  saved PC
              +64  saved PSL
              +68  saved R0
@@ -111,7 +130,7 @@
 
         /* The stack now looks like:
 
-           SP:   saved user SP
+           SP:   saved SP for previous mode
              +4  saved PC (maybe modified by exception handler)
              +8  saved PSL (end of struct pt_regs)
             +12  saved R0 (maybe modified by exception handler)
@@ -135,7 +154,7 @@
 
         /* The stack now looks like:
 
-           SP:   saved user SP
+           SP:   saved SP for previous mode
              +4  saved PC (maybe modified by exception handler)
              +8  saved PSL (end of struct pt_regs)
             +12  saved R0 (maybe modified by exception handler)