[Qemu-devel] PATCH: allow i386 debugging when segment offset != 0

[Eddie Kohler <kohler@cs.ucla.edu>]

Hi all,

This patch makes QEMU's gdb debugging stub and CPU breakpoints work when
the segment offset is not 0.

Previously, the debugging stub assumed the segment offset was 0, leading
to very odd behavior.

This patch assumes that the code segment and data segment have the same
offset.  This is a reasonable assumption.  Making the code work for
different code and data offsets would be more invasive.

Please accept this patch (this is a resend.)

Eddie Kohler


Index: target-i386/helper2.c
===================================================================
RCS file: /sources/qemu/qemu/target-i386/helper2.c,v
retrieving revision 1.62
diff -u -r1.62 helper2.c
--- target-i386/helper2.c	24 Dec 2007 14:04:06 -0000	1.62
+++ target-i386/helper2.c	6 Mar 2008 22:46:46 -0000
@@ -1081,6 +1081,7 @@
  {
      uint32_t pde_addr, pte_addr;
      uint32_t pde, pte, paddr, page_offset, page_size;
+    addr += env->segs[R_DS].base;

      if (env->cr[4] & CR4_PAE_MASK) {
          uint32_t pdpe_addr, pde_addr, pte_addr;
Index: target-i386/translate.c
===================================================================
RCS file: /sources/qemu/qemu/target-i386/translate.c,v
retrieving revision 1.79
diff -u -r1.79 translate.c
--- target-i386/translate.c	24 Feb 2008 07:45:42 -0000	1.79
+++ target-i386/translate.c	6 Mar 2008 22:46:46 -0000
@@ -6740,7 +6740,7 @@
      for(;;) {
          if (env->nb_breakpoints > 0) {
              for(j = 0; j < env->nb_breakpoints; j++) {
-                if (env->breakpoints[j] == pc_ptr) {
+                if (env->breakpoints[j] == pc_ptr - dc->cs_base) {
                      gen_debug(dc, pc_ptr - dc->cs_base);
                      break;
                  }