[Qemu-devel] [PATCH 4/5] Report exact PC on watchpoint hit

[Jan Kiszka <jan.kiszka@web.de>]

Watchpoints may hit us right in the middle of a TB, but so far we
complete the TB before servicing the breakpoint trap. This patch picks
up the preexisting feature of QEMU to leave a TB immediately if the
underlying memory page changes. The result is that the exact
instruction pointer is reported back to gdb. This improves the
usefulness of watchpoints significantly!

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
---
 exec.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: b/exec.c
===================================================================
--- a/exec.c
+++ b/exec.c
@@ -2382,6 +2382,7 @@ static target_ulong check_watchpoint(tar
                                      int len, int type)
 {
     CPUState *env = cpu_single_env;
+    target_phys_addr_t tb_addr;
     target_ulong watch;
     target_ulong retaddr;
     int i;
@@ -2395,6 +2396,11 @@ static target_ulong check_watchpoint(tar
                 (env->watchpoint[i].type == type ||
                  env->watchpoint[i].type == GDB_WATCHPOINT_ACCESS)) {
                 env->watchpoint_hit = i + 1;
+                if (env->current_tb) {
+                    tb_addr = env->current_tb->page_addr[0];
+                    tb_invalidate_phys_page_range(tb_addr,
+                                            tb_addr+TARGET_PAGE_SIZE-1, 1);
+                }
                 cpu_interrupt(env, CPU_INTERRUPT_DEBUG);
                 break;
             }