kern, arm: Dump dmesg on kernel panic/oops

Add helper functions to dump the guest kernel's dmesg buffer to a text
file in m5out. This functionality is split into two parts. First, a
dmesg dump function that can be used in other places:

void Linux::dumpDmesg(ThreadContext *, std::ostream &)

This function is used to implement two PCEvents: DmesgDumpEvent and
KernelPanic event. The only difference between the two is that the
latter produces a gem5 panic instead of a warning in addition to
dumping the kernel log.

Change-Id: I6d2af1d666ace57124089648ea906f6c787ac63c
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Gabor Dozsa <gabor.dozsa@arm.com>

1 files changed, 148 insertions, 0 deletions

diff --git a/src/kern/linux/helpers.cc b/src/kern/linux/helpers.cc
new file mode 100644
index 000000000..54fc42138
--- /dev/null
+++ b/src/kern/linux/helpers.cc
@@ -0,0 +1,148 @@
+/*
+ * Copyright (c) 2016 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Andreas Sandberg
+ */
+
+#include "kern/linux/helpers.hh"
+
+#include "arch/isa_traits.hh"
+#include "config/the_isa.hh"
+#include "cpu/thread_context.hh"
+#include "mem/fs_translating_port_proxy.hh"
+#include "sim/system.hh"
+
+struct DmesgEntry {
+    uint64_t ts_nsec;
+    uint16_t len;
+    uint16_t text_len;
+    uint16_t dict_len;
+    uint8_t facility;
+    uint8_t flags;
+} M5_ATTR_PACKED;
+
+static int
+dumpDmesgEntry(const uint8_t *base, const uint8_t *end, std::ostream &os)
+{
+    const size_t max_length = end - base;
+    DmesgEntry de;
+
+    if (max_length < sizeof(de)) {
+        warn("Malformed dmesg entry\n");
+        return -1;
+    }
+
+    memcpy(&de, base, sizeof(de));
+    de.ts_nsec = TheISA::gtoh(de.ts_nsec);
+    de.len = TheISA::gtoh(de.len);
+    de.text_len = TheISA::gtoh(de.text_len);
+
+    if (de.len < sizeof(de) ||
+        max_length < de.len ||
+        max_length < sizeof(DmesgEntry) + de.text_len) {
+
+        warn("Malformed dmesg entry:\n");
+        warn("\tMax length: %i\n", max_length);
+        warn("\tde.len: %i\n", de.len);
+        warn("\tde.text_len: %i\n", de.text_len);
+        return -1;
+    }
+
+    ccprintf(os, "[%.6f] ", de.ts_nsec * 10e-9);
+    os.write((char *)base + sizeof(de), de.text_len);
+    os << std::endl;
+
+    return de.len;
+}
+
+void
+Linux::dumpDmesg(ThreadContext *tc, std::ostream &os)
+{
+    System *system = tc->getSystemPtr();
+    const SymbolTable *symtab = system->kernelSymtab;
+    FSTranslatingPortProxy proxy(tc);
+
+    Addr addr_lb = 0, addr_lb_len = 0, addr_first = 0, addr_next = 0;
+    const bool found_symbols =
+        symtab->findAddress("__log_buf", addr_lb) &&
+        symtab->findAddress("log_buf_len", addr_lb_len) &&
+        symtab->findAddress("log_first_idx", addr_first) &&
+        symtab->findAddress("log_next_idx", addr_next);
+
+    if (!found_symbols) {
+        warn("Failed to find kernel dmesg symbols.\n");
+        return;
+    }
+
+    uint32_t log_buf_len = proxy.readGtoH<uint32_t>(addr_lb_len);
+    uint32_t log_first_idx = proxy.readGtoH<uint32_t>(addr_first);
+    uint32_t log_next_idx = proxy.readGtoH<uint32_t>(addr_next);
+
+    if (log_first_idx >= log_buf_len || log_next_idx >= log_buf_len) {
+        warn("dmesg pointers/length corrupted\n");
+        return;
+    }
+
+    // Normalize and read the dmesg ring buffer
+    std::vector<uint8_t> log_buf(log_buf_len);
+    int length;
+    if (log_first_idx < log_next_idx) {
+        length = log_next_idx - log_first_idx;
+        if (length < 0 || length > log_buf.size()) {
+            warn("Unexpected dmesg buffer length\n");
+            return;
+        }
+        proxy.readBlob(addr_lb + log_first_idx, log_buf.data(), length);
+    } else {
+        const int length_2 = log_buf_len - log_first_idx;
+        if (length_2 < 0 || length_2 + log_next_idx > log_buf.size()) {
+            warn("Unexpected dmesg buffer length\n");
+            return;
+        }
+        length = log_buf_len;
+        proxy.readBlob(addr_lb + log_first_idx, log_buf.data(), length_2);
+        proxy.readBlob(addr_lb, log_buf.data() + length_2, log_next_idx);
+    }
+
+    // Print dmesg buffer content
+    const uint8_t *cur = log_buf.data(), *end = log_buf.data() + length;
+    while (cur < end) {
+        int ret = dumpDmesgEntry(cur, end, os);
+        if (ret < 0)
+            return;
+        cur += ret;
+    }
+}