From 9bb6050d40b9936beda5cb1cd15040f6c1b07179 Mon Sep 17 00:00:00 2001
From: Amaury Pouly <amaury.pouly@gmail.com>
Date: Wed, 18 Jan 2017 14:36:27 +0100
Subject: hwstub: rewrite exception catching

Since we can catch exceptions like data aborts on read/write, it takes very
little to also catch exceptions in calls. When extending this with the catching
of illegal instructions, the call instruction now becomes much more robust and
also for address and instruction probing. Since we can catch several types of
exception, rename set_data_abort_jmp to set_exception_jmp. At the same time,
simplify the logic in read/write request handlers. Also fix a bug in ARM
jump code: it was using
  stmia r1, {..., pc}
as if pc would get current pc + 8 but this is actually implementation defined
on older ARMs (typically pc + 12) and deprecated on newer ARMs, so rewrite the
code avoid that. The set_exception_jmp() function now also reports the exception
type.

Change-Id: Icd0dd52d2456b361b27c4776be09c3d13528ed93
---
 utils/hwstub/stub/asm/mips/system.S | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

(limited to 'utils/hwstub/stub/asm/mips/system.S')

diff --git a/utils/hwstub/stub/asm/mips/system.S b/utils/hwstub/stub/asm/mips/system.S
index 2d89bde096..7f619c6edd 100644
--- a/utils/hwstub/stub/asm/mips/system.S
+++ b/utils/hwstub/stub/asm/mips/system.S
@@ -19,23 +19,24 @@
  ****************************************************************************/
 #include "mips.h"
 #include "target-config.h"
+#include "system.h"
 
-/* Handling of data abort:
+/* Handling of exception:
  * the code can register a "longjmp" buffer to restore the context in case of
  * fault */
 .data
-.global data_abort_jmp_ctx_ptr
-data_abort_jmp_ctx_ptr:
+.global exception_jmp_ctx_ptr
+exception_jmp_ctx_ptr:
 /* buffer contains in order: s0-s7, sp, s8, ra */
 .skip   44 /* = 4 * (9 callee saved registers + sp + ra) */
 
 .set noreorder
 .section .icode, "ax", %progbits
-/* Prototype: int set_data_abort_jmp()
+/* Prototype: int set_exception_jmp()
  * Return: 1 in case of data abort, 0 otherwise */
-.global set_data_abort_jmp
-set_data_abort_jmp:
-    la v0,  data_abort_jmp_ctx_ptr
+.global set_exception_jmp
+set_exception_jmp:
+    la v0,  exception_jmp_ctx_ptr
     sw s0,  0(v0)
     sw s1,  4(v0)
     sw s2,  8(v0)
@@ -50,10 +51,12 @@ set_data_abort_jmp:
     jr ra
     move v0, zero
 
-/* restore context on read/write error, performs the interrupt return */
-.global restore_data_abort_jmp
-restore_data_abort_jmp:
-la k1, data_abort_jmp_ctx_ptr
+/* restore context on read/write error, performs the interrupt return
+ * arguments:
+ * a0: exception type (EXCEPTION_*) */
+.global restore_exception_jmp
+restore_exception_jmp:
+    la k1, exception_jmp_ctx_ptr
     lw s0,  0(k1)
     lw s1,  4(k1)
     lw s2,  8(k1)
@@ -73,7 +76,7 @@ la k1, data_abort_jmp_ctx_ptr
 #else
     ehb
 #endif
-    li v0, 1
+    move v0, a0 /* set exception type */
     eret
     nop
 .set reorder
-- 
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