verify_namelist() uses strings command and scans full part of vmlinux
file to find linux_banner string. However, vmlinux file is quite large
these days, reaching over 500MB. As a result, this degradates start-up
time of crash command 10 or more seconds. (Of course, this depends on
machines you use for investigation, but I guess typically we cannot
use such powerful machines to investigate crash dump...)
To resolve this issue, let's use bfd library and read linux_banner
string in vmlinux file directly.
A simple benchmark shows the following result:
Without the fix:
# cat ./commands.txt
quit
# time ./crash -i ./commands.txt \
/usr/lib/debug/lib/modules/5.16.15-201.fc35.x86_64/vmlinux \
/var/crash/*/vmcore >/dev/null 2>&1
real 0m20.251s
user 0m19.022s
sys 0m1.054s
With the fix:
# time ./crash -i ./commands.txt \
/usr/lib/debug/lib/modules/5.16.15-201.fc35.x86_64/vmlinux \
/var/crash/*/vmcore >/dev/null 2>&1
real 0m6.528s
user 0m6.143s
sys 0m0.431s
Note that this commit keeps the original logic that uses strings
command for backward compatibility for in case.
Signed-off-by: HATAYAMA Daisuke <[email protected]>
---
Makefile | 2 +-
kernel.c | 41 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 42 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index 007d030..e520b12 100644
--- a/Makefile
+++ b/Makefile
@@ -364,7 +364,7 @@ task.o: ${GENERIC_HFILES} task.c
${CC} -c ${CRASH_CFLAGS} task.c ${WARNING_OPTIONS} ${WARNING_ERROR}
kernel.o: ${GENERIC_HFILES} kernel.c
- ${CC} -c ${CRASH_CFLAGS} kernel.c ${WARNING_OPTIONS} ${WARNING_ERROR}
+ ${CC} -c ${CRASH_CFLAGS} kernel.c -I${BFD_DIRECTORY}
-I${GDB_INCLUDE_DIRECTORY} ${WARNING_OPTIONS} ${WARNING_ERROR}
printk.o: ${GENERIC_HFILES} printk.c
${CC} -c ${CRASH_CFLAGS} printk.c ${WARNING_OPTIONS} ${WARNING_ERROR}
diff --git a/kernel.c b/kernel.c
index 1c63447..92434a3 100644
--- a/kernel.c
+++ b/kernel.c
@@ -23,6 +23,11 @@
#include <ctype.h>
#include <stdbool.h>
#include "xendump.h"
+#if defined(GDB_7_6) || defined(GDB_10_2)
+#define __CONFIG_H__ 1
+#include "config.h"
+#endif
+#include "bfd.h"
static void do_module_cmd(ulong, char *, ulong, char *, char *);
static void show_module_taint(void);
@@ -97,6 +102,7 @@ static void dump_printk_safe_seq_buf(int);
static char *vmcoreinfo_read_string(const char *);
static void check_vmcoreinfo(void);
static int is_pvops_xen(void);
+static int get_linux_banner_from_vmlinux(char *, size_t);
/*
@@ -1324,6 +1330,12 @@ verify_namelist()
target_smp = strstr(kt->utsname.version, " SMP ") ? TRUE : FALSE;
namelist_smp = FALSE;
+ if (get_linux_banner_from_vmlinux(buffer, sizeof(buffer)) &&
+ strstr(buffer, kt->proc_version)) {
+ found = TRUE;
+ goto found;
+ }
+
sprintf(command, "/usr/bin/strings %s", namelist);
if ((pipe = popen(command, "r")) == NULL) {
error(INFO, "%s: %s\n", namelist, strerror(errno));
@@ -1384,6 +1396,7 @@ verify_namelist()
}
}
+found:
if (found) {
if (CRASHDEBUG(1)) {
fprintf(fp, "verify_namelist:\n");
@@ -11770,3 +11783,31 @@ check_vmcoreinfo(void)
}
}
}
+
+static
+int get_linux_banner_from_vmlinux(char *buf, size_t size)
+{
+ struct bfd_section *sect;
+ long offset;
+
+ sect = bfd_get_section_by_name(st->bfd, ".rodata");
+ if (!sect)
+ return FALSE;
+
+ /*
+ * Although symbol_value() returns dynamic symbol value that
+ * is affected by kaslr, which is different from static symbol
+ * value in vmlinux file, but relative offset to linux_banner
+ * object in .rodata section is idential.
+ */
+ offset = symbol_value("linux_banner") - symbol_value(".rodata");
+
+ if (!bfd_get_section_contents(st->bfd,
+ sect,
+ buf,
+ offset,
+ size))
+ return FALSE;
+
+ return TRUE;
+}
--
2.31.1
--
Crash-utility mailing list
[email protected]
https://listman.redhat.com/mailman/listinfo/crash-utility
Contribution Guidelines: https://github.com/crash-utility/crash/wiki
