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@gmail.com> Signed-off-by: Alexandre Julliard <julliard@winehq.org>

winedbg/gdbproxy: Replace memory read over a breakpoint with the real value.
eb63a5f3 · Zebediah Figura · Alexandre Julliard · d1e9694e · eb63a5f3
Commit eb63a5f3 authored Jan 14, 2018 by Zebediah Figura Committed by Alexandre Julliard Jan 19, 2018
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gdbproxy.c programs/winedbg/gdbproxy.c +23 -2

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--- a/programs/winedbg/gdbproxy.c
+++ b/programs/winedbg/gdbproxy.c
@@ -1568,6 +1568,28 @@ 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;
@@ -1584,8 +1606,7 @@ 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);