Changeset 418 for trunk/hal/tsar_mips32/core

Timestamp:

Jan 8, 2018, 2:25:39 PM (7 years ago)

Author:

alain

Message:

Fix a bug in hal_kentry.S : the "uzone" pointer in the thread descriptor
must not be modified in case of interrupt.

Location:

trunk/hal/tsar_mips32/core

Files:

• hal_kentry.S (modified) (12 diffs)
• hal_syscall.c (modified) (3 diffs)

trunk/hal/tsar_mips32/core/hal_kentry.S

@@ -99 +99 @@
         
 #------------------------------------------------------------------------------------
-# This code is executed when the core is in user mode:
+# This code is executed when the core is in user mode,
+# to handle a syscall, an interrupt, or an user exception.
 # - save current c2_mode in $26.
 # - set MMU OFF.
-# - save user stack pointer in $27.
-# - set kernel stack pointer in $29.
+# - copy user stack pointer in $27 to be saved in uzone.
+# - set kernel stack pointer in $29 == top_kernel_stack(this).
 
 user_mode:
@@ -117 +118 @@
 
 #------------------------------------------------------------------------------------
-# This code is executed when the core is already in kernel mode:
+# This code is executed when the core is already in kernel mode,
+# after a syscall, to handle an interrupt.
 # - save current c2_mode in $26.
 # - set MMU OFF.
-# - save current kernel stack pointer in $27.
+# - copy current kernel stack pointer in $27.
 
 kernel_mode:
@@ -134 +136 @@
 # - $26 contains the previous c2_mode value.
 # - $27 contains the previous sp value (can be usp or ksp).
-# - $29 contains the kernel stack pointer.
+# - $29 contains the curren kernel stack pointer.
 # We execute the following actions:
-# - allocate an uzone in kernel stack, decrementing $29.
+# - decrement $29 to allocate an uzone in kernel stack
 # - save relevant GPR, CP0 and CP2 registers to uzone.
 # - set the SR in kernel mode: IRQ disabled, clear exl.
@@ -198 +200 @@
         mtc0    $3,         $12                         # set new c0_sr 
 
-#if CONFIG_KENTRY_DEBUG
+#-----------------------
+#if CONFIG_KENTRY_DEBUG 
 
     # display "enter" message
@@ -207 +210 @@
     jal     putx
     nop
+    la      $4,     msg_cycle
+    jal     puts
+    nop
+    jal     hal_time_stamp
+    nop
+    move    $4,     $2
+    jal     putx
+    nop
     la      $4,     msg_crlf
     jal     puts
@@ -270 +281 @@
     jal     puts
     nop    
-        
+
 #endif
+#-----
     
 #------------------------------------------------------------------------------------
-# This code update the uzone field in thread descriptor, 
-# and call the relevant Interrupt / Exception / Syscall handler,
+# This code calls the relevant Interrupt / Exception / Syscall handler,
 # depending on XCODE in CP0_CR.
-# assumption: $29 contains the kernel stack pointer, that is the uzone base.
+# In case of syscall or exception, it set the "uzone" pointer in thread descriptor,
+# that is used by the hal_do_syscall() & hal_do_exception() functions.
+# WARNING: This "uzone" pointer is NOT modified in case of interrupt,
+# because syscalls can be interrupted, and we want preserve this pointer.
 
         mfc0    $17,    $13                 # $17 <= CR
         andi    $17,    $17,   0x3F         # $17 <= XCODE
-
-        mfc0    $4,     $4,   2             # $4 <= pointer on thread desc
-    sw      $29,    8($4)               # update uzone pointer in thread desc
-
         ori         $8,     $0,   0x20
     beq     $8,     $17,  cause_sys     # go to syscall handler
@@ -292 +302 @@
 
 cause_excp:
+        mfc0    $4,     $4,   2             # get pointer on thread desc
+    sw      $29,    8($4)               # update uzone pointer in thread desc
         jal     hal_do_exception            # call exception handler
         nop
@@ -298 +310 @@
 
 cause_sys:
+        mfc0    $4,     $4,   2             # get pointer on thread desc
+    sw      $29,    8($4)               # update uzone pointer in thread desc
         jal     hal_do_syscall              # call syscall handler                 
     nop
@@ -309 +323 @@
 # -----------------------------------------------------------------------------------
 # Kernel exit
-# The pointer on uzone is supposed to be contained in $29
+# - All registers saved in the uzone are restored, using the pointer on uzone,
+#   that is contained in $29.
+# - The "uzone" field in thread descriptor, that has beeen modified at kernel entry
+#   is restored from value contained in the uzone[UZ_SP] slot. 
 # -----------------------------------------------------------------------------------
+
 kentry_exit:
 
+#----------------------
 #if CONFIG_KENTRY_DEBUG
 
@@ -322 +341 @@
     jal     putx
     nop
+    la      $4,     msg_cycle
+    jal     puts
+    nop
+    jal     hal_time_stamp
+    nop
+    move    $4,     $2
+    jal     putx
+    nop
     la      $4,     msg_crlf
     jal     puts
@@ -387 +414 @@
         
 #endif
+#-----
     
         # restore registers from uzone
@@ -475 +503 @@
     .align 2
     .asciiz "\nexit kernel : &uzone = " 
-
+msg_cycle:
+    .align 2
+    .asciiz " / cycle = "
+

trunk/hal/tsar_mips32/core/hal_syscall.c

@@ -29 +29 @@
 #include <hal_kentry.h>
 
+// @@@
+// __attribute__((section(".kdata"))) uint32_t * enter_uzone;
+// __attribute__((section(".kdata"))) uint32_t * exit_uzone;
+// @@@
 
 /////////////////////
@@ -69 +73 @@
     exit_uzone = (uint32_t *)this->uzone;
 
+// printk("\n@@@ %s exit : enter_uzone = %x / exit_uzone = %x\n",
+// __FUNCTION__ , enter_uzone , exit_uzone );
+
     // set syscall return value to uzone 
         exit_uzone[UZ_V0] = retval;
@@ -75 +82 @@
         exit_uzone[UZ_EPC] += 4;
 
+    hal_fence();
 }