[PATCH v8 11/22] scripts/gdb: Add lx-dmesg command

[Jan Kiszka]

This pokes into the log buffer of the debugged kernel, dumping it to the
gdb console. Helping in case the target should or can no longer execute
dmesg itself.

CC: Kay Sievers <kay@xxxxxxxx>
Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
 scripts/gdb/linux/dmesg.py | 64 ++++++++++++++++++++++++++++++++++++++++++++++
 scripts/gdb/vmlinux-gdb.py |  1 +
 2 files changed, 65 insertions(+)
 create mode 100644 scripts/gdb/linux/dmesg.py

diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py
new file mode 100644
index 0000000..7650f24
--- /dev/null
+++ b/scripts/gdb/linux/dmesg.py
@@ -0,0 +1,64 @@
+#
+# gdb helper commands and functions for Linux kernel debugging
+#
+#  kernel log buffer dump
+#
+# Copyright (c) Siemens AG, 2011, 2012
+#
+# Authors:
+#  Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
+#
+# This work is licensed under the terms of the GNU GPL version 2.
+#
+
+import gdb
+import string
+
+from linux import utils
+
+
+class LxDmesg(gdb.Command):
+    """Print Linux kernel log buffer."""
+
+    def __init__(self):
+        super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA)
+
+    def invoke(self, arg, from_tty):
+        log_buf_addr = int(str(gdb.parse_and_eval("log_buf")).split()[0], 16)
+        log_first_idx = int(gdb.parse_and_eval("log_first_idx"))
+        log_next_idx = int(gdb.parse_and_eval("log_next_idx"))
+        log_buf_len = int(gdb.parse_and_eval("log_buf_len"))
+
+        inf = gdb.inferiors()[0]
+        start = log_buf_addr + log_first_idx
+        if log_first_idx < log_next_idx:
+            log_buf_2nd_half = -1
+            length = log_next_idx - log_first_idx
+            log_buf = inf.read_memory(start, length)
+        else:
+            log_buf_2nd_half = log_buf_len - log_first_idx
+            log_buf = inf.read_memory(start, log_buf_2nd_half) + \
+                inf.read_memory(log_buf_addr, log_next_idx)
+
+        pos = 0
+        while pos < log_buf.__len__():
+            length = utils.read_u16(log_buf[pos + 8:pos + 10])
+            if length == 0:
+                if log_buf_2nd_half == -1:
+                    gdb.write("Corrupted log buffer!\n")
+                    break
+                pos = log_buf_2nd_half
+                continue
+
+            text_len = utils.read_u16(log_buf[pos + 10:pos + 12])
+            time_stamp = utils.read_u64(log_buf[pos:pos + 8])
+
+            for line in log_buf[pos + 16:pos + 16 + text_len].splitlines():
+                gdb.write("[{time:12.6f}] {line}\n".format(
+                    time=time_stamp / 1000000000.0,
+                    line=line))
+
+            pos += length
+
+
+LxDmesg()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index cf2e716..fa66d23 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -25,3 +25,4 @@ else:
     import linux.utils
     import linux.symbols
     import linux.modules
+    import linux.dmesg
-- 
1.8.1.1.298.ge7eed54

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