[Qemu-devel] [PATCH 6/6] gdbstub: add qSymbol handling for TARGET_MIPS

[Nathan Froyd]

QEMU needs to know the address of _mdi_syscall so that breakpoints can
be set appropriately.  But if QEMU is started from within GDB as:

  (gdb) target remote | qemu -M mipssim -s -S ... -kernel /dev/null
  ...
  (gdb) load

then QEMU's ELF loader never gets a chance to grovel through the ELF
file to look for the .sdeosabi section.

Therefore, the GDB stub needs to know how to ask GDB for the address of
_mdi_syscall so that the necessary breakpoint can be set.

Signed-off-by: Nathan Froyd <address@hidden>
---
 gdbstub.c |   29 +++++++++++++++++++++++++++++
 1 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/gdbstub.c b/gdbstub.c
index bb38971..d881a66 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -1937,6 +1937,35 @@ static int gdb_handle_packet(GDBState *s, const char 
*line_buf)
                 put_packet(s, buf);
             }
             break;
+        } else if (strncmp(p, "Symbol:", 7) == 0) {
+#if defined(TARGET_MIPS) && !defined(TARGET_MIPS64) && 
!defined(CONFIG_USER_ONLY)
+#define MDI_SYSCALL_SYMBOL "_mdi_syscall"
+            if (strncmp(p+7, ":", 1) == 0) {
+                /* GDB is telling us we can ask for symbols.  Look for
+                   _mdi_syscall.  */
+                memtohex((char *)mem_buf, (const uint8_t *)MDI_SYSCALL_SYMBOL,
+                         strlen(MDI_SYSCALL_SYMBOL));
+                mem_buf[strlen(MDI_SYSCALL_SYMBOL)*2] = 0;
+                snprintf(buf, sizeof(buf), "qSymbol:%s", mem_buf);
+                put_packet(s, buf);
+                break;
+            } else {
+                /* A response from a previous query.  */
+                if (*(p+7) != ':') {
+                    addr = strtoull(p+7, (char **)&p, 16);
+                    hextomem(mem_buf, p+1, strlen(MDI_SYSCALL_SYMBOL)*2);
+
+                    if (memcmp(mem_buf, MDI_SYSCALL_SYMBOL,
+                               strlen(MDI_SYSCALL_SYMBOL)) == 0) {
+                        install_semihosting_breakpoint(s->c_cpu, addr);
+                    }
+                }
+            }
+            /* All done, regardless of whether we got the right symbol.  */
+            put_packet(s, "OK");
+            break;
+#undef MDI_SYSCALL_SYMBOL                
+#endif
         }
 #ifdef CONFIG_USER_ONLY
         else if (strncmp(p, "Offsets", 7) == 0) {
-- 
1.6.3.2