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133 lines
3.6 KiB
133 lines
3.6 KiB
Subject: [PATCH] add syslog printing to xmon debugger.
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From: Linas Vepstas <linas@austin.ibm.com>
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Patch-mainline: Not yet
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This patch 'dmesg'/printk log buffer printing to xmon. I find this
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useful because crashes are almost always preceeded by interesting
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printk's. This patch is simple & straightforward, except for one
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possibly controversial aspect: it embeds a small snippet in
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kernel/printk.c to return the location of the syslog. This is
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needed because kallsyms and even CONFIG_KALLSYMS_ALL is not enough
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to reveal the location of log_buf. This code is about 90%
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cut-n-paste of earlier code from Keith Owens.
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Signed-off-by: Olaf Hering <olh@suse.de>
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---
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arch/powerpc/xmon/xmon.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++
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kernel/printk.c | 15 ++++++++++++
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2 files changed, 72 insertions(+)
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--- a/arch/powerpc/xmon/xmon.c
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+++ b/arch/powerpc/xmon/xmon.c
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@@ -138,6 +138,7 @@ static struct bpt *in_breakpoint_table(u
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static int do_step(struct pt_regs *);
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static void bpt_cmds(void);
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static void cacheflush(void);
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+static void xmon_show_dmesg(void);
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static int cpu_cmd(void);
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static void csum(void);
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static void bootcmds(void);
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@@ -194,6 +195,7 @@ Commands:\n\
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#endif
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"\
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C checksum\n\
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+ D show dmesg (printk) buffer\n\
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d dump bytes\n\
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di dump instructions\n\
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df dump float values\n\
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@@ -828,6 +830,9 @@ cmds(struct pt_regs *excp)
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case 'd':
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dump();
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break;
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+ case 'D':
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+ xmon_show_dmesg();
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+ break;
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case 'l':
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symbol_lookup();
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break;
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@@ -2599,6 +2604,58 @@ static void xmon_print_symbol(unsigned l
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printf("%s", after);
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}
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+extern void debugger_syslog_data(char *syslog_data[4]);
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+#define SYSLOG_WRAP(p) if (p < syslog_data[0]) p = syslog_data[1]-1; \
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+ else if (p >= syslog_data[1]) p = syslog_data[0];
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+
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+static void xmon_show_dmesg(void)
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+{
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+ char *syslog_data[4], *start, *end, c;
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+ int logsize;
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+
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+ /* syslog_data[0,1] physical start, end+1.
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+ * syslog_data[2,3] logical start, end+1.
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+ */
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+ debugger_syslog_data(syslog_data);
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+ if (syslog_data[2] == syslog_data[3])
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+ return;
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+ logsize = syslog_data[1] - syslog_data[0];
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+ start = syslog_data[0] + (syslog_data[2] - syslog_data[0]) % logsize;
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+ end = syslog_data[0] + (syslog_data[3] - syslog_data[0]) % logsize;
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+
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+ /* Do a line at a time (max 200 chars) to reduce overhead */
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+ c = '\0';
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+ while(1) {
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+ char *p;
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+ int chars = 0;
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+ if (!*start) {
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+ while (!*start) {
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+ ++start;
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+ SYSLOG_WRAP(start);
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+ if (start == end)
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+ break;
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+ }
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+ if (start == end)
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+ break;
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+ }
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+ p = start;
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+ while (*start && chars < 200) {
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+ c = *start;
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+ ++chars;
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+ ++start;
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+ SYSLOG_WRAP(start);
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+ if (start == end || c == '\n')
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+ break;
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+ }
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+ if (chars)
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+ printf("%.*s", chars, p);
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+ if (start == end)
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+ break;
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+ }
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+ if (c != '\n')
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+ printf("\n");
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+}
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+
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#ifdef CONFIG_PPC_BOOK3S_64
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static void dump_slb(void)
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{
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--- a/kernel/printk.c
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+++ b/kernel/printk.c
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@@ -413,6 +413,21 @@ SYSCALL_DEFINE3(syslog, int, type, char
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return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
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}
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+#ifdef CONFIG_DEBUG_KERNEL
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+/* Its very handy to be able to view the syslog buffer during debug.
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+ * But do_syslog() uses locks so it cannot be used during debugging.
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+ * Instead, provide the start and end of the physical and logical logs.
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+ * This is equivalent to do_syslog(3).
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+ */
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+void debugger_syslog_data(char *syslog_data[4])
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+{
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+ syslog_data[0] = log_buf;
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+ syslog_data[1] = log_buf + log_buf_len;
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+ syslog_data[2] = log_buf + log_end - (logged_chars < log_buf_len ? logged_chars : log_buf_len);
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+ syslog_data[3] = log_buf + log_end;
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+}
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+#endif /* CONFIG_DEBUG_KERNEL */
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+
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/*
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* Call the console drivers on a range of log_buf
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*/
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