Zebediah Figura : winedbg/gdbproxy: Replace memory read over a breakpoint with the real value.

[Alexandre Julliard]

Module: wine
Branch: oldstable
Commit: e46cfd0fbec434a7258f56c7780016f6b3123567
URL:    https://source.winehq.org/git/wine.git/?a=commit;h=e46cfd0fbec434a7258f56c77...

Author: Zebediah Figura <z.figura12(a)gmail.com>
Date:   Sun Jan 14 19:01:15 2018 -0600

winedbg/gdbproxy: Replace memory read over a breakpoint with the real value.

Normally, when we hit a breakpoint, we remove it before stopping and add it
after continuing. gdb, however, reads the process memory before requesting
that the breakpoint be removed, and apparently caches it until the `stepi`
instruction is executed; as a result, it thinks that the interrupt byte that
is present in the code is an actual interrupt and not a breakpoint, and so
tries to step over it as one byte instead of executing the real instruction
at that location.

Signed-off-by: Zebediah Figura <z.figura12(a)gmail.com>
Signed-off-by: Alexandre Julliard <julliard(a)winehq.org>
(cherry picked from commit eb63a5f3c3c1851f212bd14f91da329bf3166e42)
Signed-off-by: Michael Stefaniuc <mstefani(a)winehq.org>

---

 programs/winedbg/gdbproxy.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/programs/winedbg/gdbproxy.c b/programs/winedbg/gdbproxy.c
index f94fef5..400f6de 100644
--- a/programs/winedbg/gdbproxy.c
+++ b/programs/winedbg/gdbproxy.c
@@ -1499,6 +1499,28 @@ static enum packet_return packet_thread(struct gdb_context* gdbctx)
     }
 }
 
+static BOOL read_memory(struct gdb_context *gdbctx, char *addr, char *buffer, SIZE_T blk_len, SIZE_T *r)
+{
+    /* Wrapper around process_io->read() that replaces values displaced by breakpoints. */
+
+    BOOL ret;
+
+    ret = gdbctx->process->process_io->read(gdbctx->process->handle, addr, buffer, blk_len, r);
+    if (ret)
+    {
+        struct gdb_ctx_Xpoint *xpt;
+
+        for (xpt = &gdbctx->Xpoints[NUM_XPOINT - 1]; xpt >= gdbctx->Xpoints; xpt--)
+        {
+            char *xpt_addr = xpt->addr;
+
+            if (xpt->type != -1 && xpt_addr >= addr && xpt_addr < addr + blk_len)
+                buffer[xpt_addr - addr] = xpt->val;
+        }
+    }
+    return ret;
+}
+
 static enum packet_return packet_read_memory(struct gdb_context* gdbctx)
 {
     char               *addr;
@@ -1515,8 +1537,7 @@ static enum packet_return packet_read_memory(struct gdb_context* gdbctx)
     for (nread = 0; nread < len; nread += r, addr += r)
     {
         blk_len = min(sizeof(buffer), len - nread);
-        if (!gdbctx->process->process_io->read(gdbctx->process->handle, addr, buffer, blk_len, &r) ||
-            r == 0)
+        if (!read_memory(gdbctx, addr, buffer, blk_len, &r) || r == 0)
         {
             /* fail at first address, return error */
             if (nread == 0) return packet_reply_error(gdbctx, EFAULT);