qemu-e2k/include/qemu/error-report.h

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/*
* Error reporting
*
* Copyright (C) 2010 Red Hat Inc.
*
* Authors:
* Markus Armbruster <armbru@redhat.com>,
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef QEMU_ERROR_REPORT_H
#define QEMU_ERROR_REPORT_H
typedef struct Location {
/* all members are private to qemu-error.c */
enum { LOC_NONE, LOC_CMDLINE, LOC_FILE } kind;
int num;
const void *ptr;
struct Location *prev;
} Location;
Location *loc_push_restore(Location *loc);
Location *loc_push_none(Location *loc);
Location *loc_pop(Location *loc);
Location *loc_save(Location *loc);
void loc_restore(Location *loc);
void loc_set_none(void);
void loc_set_cmdline(char **argv, int idx, int cnt);
void loc_set_file(const char *fname, int lno);
int error_vprintf(const char *fmt, va_list ap) G_GNUC_PRINTF(1, 0);
int error_printf(const char *fmt, ...) G_GNUC_PRINTF(1, 2);
int error_vprintf_unless_qmp(const char *fmt, va_list ap) G_GNUC_PRINTF(1, 0);
int error_printf_unless_qmp(const char *fmt, ...) G_GNUC_PRINTF(1, 2);
void error_vreport(const char *fmt, va_list ap) G_GNUC_PRINTF(1, 0);
void warn_vreport(const char *fmt, va_list ap) G_GNUC_PRINTF(1, 0);
void info_vreport(const char *fmt, va_list ap) G_GNUC_PRINTF(1, 0);
void error_report(const char *fmt, ...) G_GNUC_PRINTF(1, 2);
void warn_report(const char *fmt, ...) G_GNUC_PRINTF(1, 2);
void info_report(const char *fmt, ...) G_GNUC_PRINTF(1, 2);
bool error_report_once_cond(bool *printed, const char *fmt, ...)
G_GNUC_PRINTF(2, 3);
bool warn_report_once_cond(bool *printed, const char *fmt, ...)
G_GNUC_PRINTF(2, 3);
void error_init(const char *argv0);
qemu-error: introduce {error|warn}_report_once There are many error_report()s that can be used in frequently called functions, especially on IO paths. That can be unideal in that malicious guest can try to trigger the error tons of time which might use up the log space on the host (e.g., libvirt can capture the stderr of QEMU and put it persistently onto disk). In VT-d emulation code, we have trace_vtd_error() tracer. AFAIU all those places can be replaced by something like error_report() but trace points are mostly used to avoid the DDOS attack that mentioned above. However using trace points mean that errors are not dumped if trace not enabled. It's not a big deal in most modern server managements since we have things like logrotate to maintain the logs and make sure the quota is expected. However it'll still be nice that we just provide another way to restrict message generations. In most cases, this kind of error_report()s will only provide valid information on the first message sent, and all the rest of similar messages will be mostly talking about the same thing. This patch introduces *_report_once() helpers to allow a message to be dumped only once during one QEMU process's life cycle. It will make sure: (1) it's on by deffault, so we can even get something without turning the trace on and reproducing, and (2) it won't be affected by DDOS attack. To implement it, I stole the printk_once() macro from Linux. CC: Eric Blake <eblake@redhat.com> CC: Markus Armbruster <armbru@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20180815095328.32414-2-peterx@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> [Whitespace adjusted, comments improved] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2018-08-15 11:53:26 +02:00
/*
* Similar to error_report(), except it prints the message just once.
* Return true when it prints, false otherwise.
*/
#define error_report_once(fmt, ...) \
({ \
static bool print_once_; \
error_report_once_cond(&print_once_, \
fmt, ##__VA_ARGS__); \
qemu-error: introduce {error|warn}_report_once There are many error_report()s that can be used in frequently called functions, especially on IO paths. That can be unideal in that malicious guest can try to trigger the error tons of time which might use up the log space on the host (e.g., libvirt can capture the stderr of QEMU and put it persistently onto disk). In VT-d emulation code, we have trace_vtd_error() tracer. AFAIU all those places can be replaced by something like error_report() but trace points are mostly used to avoid the DDOS attack that mentioned above. However using trace points mean that errors are not dumped if trace not enabled. It's not a big deal in most modern server managements since we have things like logrotate to maintain the logs and make sure the quota is expected. However it'll still be nice that we just provide another way to restrict message generations. In most cases, this kind of error_report()s will only provide valid information on the first message sent, and all the rest of similar messages will be mostly talking about the same thing. This patch introduces *_report_once() helpers to allow a message to be dumped only once during one QEMU process's life cycle. It will make sure: (1) it's on by deffault, so we can even get something without turning the trace on and reproducing, and (2) it won't be affected by DDOS attack. To implement it, I stole the printk_once() macro from Linux. CC: Eric Blake <eblake@redhat.com> CC: Markus Armbruster <armbru@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20180815095328.32414-2-peterx@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> [Whitespace adjusted, comments improved] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2018-08-15 11:53:26 +02:00
})
/*
* Similar to warn_report(), except it prints the message just once.
* Return true when it prints, false otherwise.
*/
#define warn_report_once(fmt, ...) \
({ \
static bool print_once_; \
warn_report_once_cond(&print_once_, \
fmt, ##__VA_ARGS__); \
qemu-error: introduce {error|warn}_report_once There are many error_report()s that can be used in frequently called functions, especially on IO paths. That can be unideal in that malicious guest can try to trigger the error tons of time which might use up the log space on the host (e.g., libvirt can capture the stderr of QEMU and put it persistently onto disk). In VT-d emulation code, we have trace_vtd_error() tracer. AFAIU all those places can be replaced by something like error_report() but trace points are mostly used to avoid the DDOS attack that mentioned above. However using trace points mean that errors are not dumped if trace not enabled. It's not a big deal in most modern server managements since we have things like logrotate to maintain the logs and make sure the quota is expected. However it'll still be nice that we just provide another way to restrict message generations. In most cases, this kind of error_report()s will only provide valid information on the first message sent, and all the rest of similar messages will be mostly talking about the same thing. This patch introduces *_report_once() helpers to allow a message to be dumped only once during one QEMU process's life cycle. It will make sure: (1) it's on by deffault, so we can even get something without turning the trace on and reproducing, and (2) it won't be affected by DDOS attack. To implement it, I stole the printk_once() macro from Linux. CC: Eric Blake <eblake@redhat.com> CC: Markus Armbruster <armbru@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <20180815095328.32414-2-peterx@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> [Whitespace adjusted, comments improved] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2018-08-15 11:53:26 +02:00
})
extern bool message_with_timestamp;
extern bool error_with_guestname;
extern const char *error_guest_name;
#endif