[Qemu-devel] [PATCH v2 0/2] trace: Forbid trailing newline in event format

[Qemu-devel] [PATCH v2 0/2] trace: Forbid trailing newline in event format

[Philippe Mathieu-Daudé]

Hi Stefan,

I'v been confused by trailing newline in trace reports,
so this series aims to fix this, by cleaning current
formats and add a check to catch new one introduced.

v2:
- Use regex format (easier to review)
- Added R-b

Regards,

Phil.

Philippe Mathieu-Daudé (2):
  trace: Remove trailing newline in events
  trace: Forbid event format ending with newline character

 docs/devel/tracing.txt        |  2 ++
 hw/misc/trace-events          | 10 +++++-----
 hw/scsi/trace-events          |  2 +-
 hw/sd/trace-events            |  2 +-
 nbd/trace-events              |  4 ++--
 net/trace-events              |  6 +++---
 scripts/tracetool/__init__.py |  3 +++
 7 files changed, 17 insertions(+), 12 deletions(-)

-- 
2.20.1

[Qemu-devel] [PATCH v2 1/2] trace: Remove trailing newline in events

[Philippe Mathieu-Daudé]

While the tracing frawework does not forbid trailing newline in
events format string, using them lead to confuse output.
It is the responsibility of the backend to properly end an event
line.

Some of our formats have trailing newlines, remove them.

Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 hw/misc/trace-events | 10 +++++-----
 hw/scsi/trace-events |  2 +-
 hw/sd/trace-events   |  2 +-
 nbd/trace-events     |  4 ++--
 net/trace-events     |  6 +++---
 5 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/hw/misc/trace-events b/hw/misc/trace-events
index c1ea1aa437..74276225f8 100644
--- a/hw/misc/trace-events
+++ b/hw/misc/trace-events
@@ -118,11 +118,11 @@ iotkit_secctl_ns_read(uint32_t offset, uint64_t data, unsigned size) "IoTKit Sec
 iotkit_secctl_ns_write(uint32_t offset, uint64_t data, unsigned size) "IoTKit SecCtl NS regs write: offset 0x%x data 0x%" PRIx64 " size %u"
 
 # imx6ul_ccm.c
-ccm_entry(void) "\n"
-ccm_freq(uint32_t freq) "freq = %d\n"
-ccm_clock_freq(uint32_t clock, uint32_t freq) "(Clock = %d) = %d\n"
-ccm_read_reg(const char *reg_name, uint32_t value) "reg[%s] <= 0x%" PRIx32 "\n"
-ccm_write_reg(const char *reg_name, uint32_t value) "reg[%s] => 0x%" PRIx32 "\n"
+ccm_entry(void) ""
+ccm_freq(uint32_t freq) "freq = %d"
+ccm_clock_freq(uint32_t clock, uint32_t freq) "(Clock = %d) = %d"
+ccm_read_reg(const char *reg_name, uint32_t value) "reg[%s] <= 0x%" PRIx32
+ccm_write_reg(const char *reg_name, uint32_t value) "reg[%s] => 0x%" PRIx32
 
 # iotkit-sysinfo.c
 iotkit_sysinfo_read(uint64_t offset, uint64_t data, unsigned size) "IoTKit SysInfo read: offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
diff --git a/hw/scsi/trace-events b/hw/scsi/trace-events
index 452b5994e6..b0820052f8 100644
--- a/hw/scsi/trace-events
+++ b/hw/scsi/trace-events
@@ -28,7 +28,7 @@ mptsas_mmio_read(void *dev, uint32_t addr, uint32_t val) "dev %p addr 0x%08x val
 mptsas_mmio_unhandled_read(void *dev, uint32_t addr) "dev %p addr 0x%08x"
 mptsas_mmio_unhandled_write(void *dev, uint32_t addr, uint32_t val) "dev %p addr 0x%08x value 0x%x"
 mptsas_mmio_write(void *dev, uint32_t addr, uint32_t val) "dev %p addr 0x%08x value 0x%x"
-mptsas_process_message(void *dev, int msg, uint32_t ctx) "dev %p cmd %d context 0x%08x\n"
+mptsas_process_message(void *dev, int msg, uint32_t ctx) "dev %p cmd %d context 0x%08x"
 mptsas_process_scsi_io_request(void *dev, int bus, int target, int lun, uint64_t len) "dev %p dev %d:%d:%d length %"PRIu64""
 mptsas_reset(void *dev) "dev %p "
 mptsas_scsi_overflow(void *dev, uint32_t ctx, uint64_t req, uint64_t found) "dev %p context 0x%08x: %"PRIu64"/%"PRIu64""
diff --git a/hw/sd/trace-events b/hw/sd/trace-events
index 52971dc033..efcff666a2 100644
--- a/hw/sd/trace-events
+++ b/hw/sd/trace-events
@@ -4,7 +4,7 @@
 bcm2835_sdhost_read(uint64_t offset, uint64_t data, unsigned size) "offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
 bcm2835_sdhost_write(uint64_t offset, uint64_t data, unsigned size) "offset 0x%" PRIx64 " data 0x%" PRIx64 " size %u"
 bcm2835_sdhost_edm_change(const char *why, uint32_t edm) "(%s) EDM now 0x%x"
-bcm2835_sdhost_update_irq(uint32_t irq) "IRQ bits 0x%x\n"
+bcm2835_sdhost_update_irq(uint32_t irq) "IRQ bits 0x%x"
 
 # core.c
 sdbus_command(const char *bus_name, uint8_t cmd, uint32_t arg) "@%s CMD%02d arg 0x%08x"
diff --git a/nbd/trace-events b/nbd/trace-events
index f6cde96790..a955918e97 100644
--- a/nbd/trace-events
+++ b/nbd/trace-events
@@ -61,8 +61,8 @@ nbd_negotiate_begin(void) "Beginning negotiation"
 nbd_negotiate_new_style_size_flags(uint64_t size, unsigned flags) "advertising size %" PRIu64 " and flags 0x%x"
 nbd_negotiate_success(void) "Negotiation succeeded"
 nbd_receive_request(uint32_t magic, uint16_t flags, uint16_t type, uint64_t from, uint32_t len) "Got request: { magic = 0x%" PRIx32 ", .flags = 0x%" PRIx16 ", .type = 0x%" PRIx16 ", from = %" PRIu64 ", len = %" PRIu32 " }"
-nbd_blk_aio_attached(const char *name, void *ctx) "Export %s: Attaching clients to AIO context %p\n"
-nbd_blk_aio_detach(const char *name, void *ctx) "Export %s: Detaching clients from AIO context %p\n"
+nbd_blk_aio_attached(const char *name, void *ctx) "Export %s: Attaching clients to AIO context %p"
+nbd_blk_aio_detach(const char *name, void *ctx) "Export %s: Detaching clients from AIO context %p"
 nbd_co_send_simple_reply(uint64_t handle, uint32_t error, const char *errname, int len) "Send simple reply: handle = %" PRIu64 ", error = %" PRIu32 " (%s), len = %d"
 nbd_co_send_structured_done(uint64_t handle) "Send structured reply done: handle = %" PRIu64
 nbd_co_send_structured_read(uint64_t handle, uint64_t offset, void *data, size_t size) "Send structured read data reply: handle = %" PRIu64 ", offset = %" PRIu64 ", data = %p, len = %zu"
diff --git a/net/trace-events b/net/trace-events
index ac57056497..02c13fd0ba 100644
--- a/net/trace-events
+++ b/net/trace-events
@@ -17,9 +17,9 @@ colo_compare_icmp_miscompare(const char *sta, int size) ": %s = %d"
 colo_compare_ip_info(int psize, const char *sta, const char *stb, int ssize, const char *stc, const char *std) "ppkt size = %d, ip_src = %s, ip_dst = %s, spkt size = %d, ip_src = %s, ip_dst = %s"
 colo_old_packet_check_found(int64_t old_time) "%" PRId64
 colo_compare_miscompare(void) ""
-colo_compare_tcp_info(const char *pkt, uint32_t seq, uint32_t ack, int hdlen, int pdlen, int offset, int flags) "%s: seq/ack= %u/%u hdlen= %d pdlen= %d offset= %d flags=%d\n"
+colo_compare_tcp_info(const char *pkt, uint32_t seq, uint32_t ack, int hdlen, int pdlen, int offset, int flags) "%s: seq/ack= %u/%u hdlen= %d pdlen= %d offset= %d flags=%d"
 
 # filter-rewriter.c
 colo_filter_rewriter_debug(void) ""
-colo_filter_rewriter_pkt_info(const char *func, const char *src, const char *dst, uint32_t seq, uint32_t ack, uint32_t flag) "%s: src/dst: %s/%s p: seq/ack=%u/%u  flags=0x%x\n"
-colo_filter_rewriter_conn_offset(uint32_t offset) ": offset=%u\n"
+colo_filter_rewriter_pkt_info(const char *func, const char *src, const char *dst, uint32_t seq, uint32_t ack, uint32_t flag) "%s: src/dst: %s/%s p: seq/ack=%u/%u  flags=0x%x"
+colo_filter_rewriter_conn_offset(uint32_t offset) ": offset=%u"
-- 
2.20.1

Re: [Qemu-devel] [PATCH v2 1/2] trace: Remove trailing newline in events

[Eric Blake]

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On 9/16/19 4:51 AM, Philippe Mathieu-Daudé wrote:
> While the tracing frawework does not forbid trailing newline in

framework

> events format string, using them lead to confuse output.
> It is the responsibility of the backend to properly end an event
> line.

Why just trailing newline? Should we not forbid ALL use of newline in a
trace message?

> 
> Some of our formats have trailing newlines, remove them.
> 
> Reviewed-by: John Snow <jsnow@redhat.com>
> Reviewed-by: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org


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Re: [Qemu-devel] [PATCH v2 1/2] trace: Remove trailing newline in events

[Philippe Mathieu-Daudé]

On 9/16/19 6:36 PM, Eric Blake wrote:
> On 9/16/19 4:51 AM, Philippe Mathieu-Daudé wrote:
>> While the tracing frawework does not forbid trailing newline in
> 
> framework
> 
>> events format string, using them lead to confuse output.
>> It is the responsibility of the backend to properly end an event
>> line.
> 
> Why just trailing newline? Should we not forbid ALL use of newline in a
> trace message?

I thought about it and forgot to add a comment when respining.
Yes, I think this is the right thing to enforce.
However it requires more cleanup, affecting more subsystems, so I'd
rather keep it for a follow-up series.

>>
>> Some of our formats have trailing newlines, remove them.
>>
>> Reviewed-by: John Snow <jsnow@redhat.com>
>> Reviewed-by: Kevin Wolf <kwolf@redhat.com>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---

Re: [Qemu-devel] [PATCH v2 1/2] trace: Remove trailing newline in events

[John Snow]

On 9/16/19 12:40 PM, Philippe Mathieu-Daudé wrote:
> On 9/16/19 6:36 PM, Eric Blake wrote:
>> On 9/16/19 4:51 AM, Philippe Mathieu-Daudé wrote:
>>> While the tracing frawework does not forbid trailing newline in
>>
>> framework
>>
>>> events format string, using them lead to confuse output.
>>> It is the responsibility of the backend to properly end an event
>>> line.
>>
>> Why just trailing newline? Should we not forbid ALL use of newline in a
>> trace message?
> 
> I thought about it and forgot to add a comment when respining.
> Yes, I think this is the right thing to enforce.
> However it requires more cleanup, affecting more subsystems, so I'd
> rather keep it for a follow-up series.

What's the problem with using multi-line trace statements?
Does it interfere with non-printf backends?

(I think I intentionally use these for AHCI in a few places.)

--js

Re: [Qemu-devel] [PATCH v2 1/2] trace: Remove trailing newline in events

[Stefan Hajnoczi]

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On Mon, Sep 16, 2019 at 12:41:44PM -0400, John Snow wrote:
> On 9/16/19 12:40 PM, Philippe Mathieu-Daudé wrote:
> > On 9/16/19 6:36 PM, Eric Blake wrote:
> >> On 9/16/19 4:51 AM, Philippe Mathieu-Daudé wrote:
> >>> While the tracing frawework does not forbid trailing newline in
> >>
> >> framework
> >>
> >>> events format string, using them lead to confuse output.
> >>> It is the responsibility of the backend to properly end an event
> >>> line.
> >>
> >> Why just trailing newline? Should we not forbid ALL use of newline in a
> >> trace message?
> > 
> > I thought about it and forgot to add a comment when respining.
> > Yes, I think this is the right thing to enforce.
> > However it requires more cleanup, affecting more subsystems, so I'd
> > rather keep it for a follow-up series.
> 
> What's the problem with using multi-line trace statements?

I agree with avoiding trailing newlines in format strings in the
./trace-events files for consistency.

Although non-trailing newlines in format strings are unusual, they could
make trace logs easier to read in complex cases.  I don't see a reason
to forbid them since we support trace backends that emit a binary log
with a parsing API - there's no need to write scripts that parse the
text output.

> (I think I intentionally use these for AHCI in a few places.)

hw/ide/ahci.c format strings do not contain newlines, so they are
technically in compliance.

ahci_pretty_buffer_fis() is used to generate a hex dump with newlines
but it's a %s format string argument to trace_handle_reg_h2d_fis_dump()
and trace_handle_cmd_fis_dump().

Stefan

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[Qemu-devel] [PATCH v2 2/2] trace: Forbid event format ending with newline character

[Philippe Mathieu-Daudé]

Event format ending with newlines confuse the trace reports.
Forbid them.

Add a check to refuse new format added with trailing newline:

  $ make
  [...]
    GEN     hw/misc/trace.h
  Traceback (most recent call last):
    File "scripts/tracetool.py", line 152, in <module>
      main(sys.argv)
    File "scripts/tracetool.py", line 143, in main
      events.extend(tracetool.read_events(fh, arg))
    File "scripts/tracetool/__init__.py", line 367, in read_events
      event = Event.build(line)
    File "scripts/tracetool/__init__.py", line 281, in build
      raise ValueError("Event format can not end with a newline character")
  ValueError: Error at hw/misc/trace-events:121: Event format can not end with a newline character

Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
v2: "\\n\"" -> r'\n"' (jsnow)
---
 docs/devel/tracing.txt        | 2 ++
 scripts/tracetool/__init__.py | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/docs/devel/tracing.txt b/docs/devel/tracing.txt
index 76e492a489..8231bbf5d1 100644
--- a/docs/devel/tracing.txt
+++ b/docs/devel/tracing.txt
@@ -112,6 +112,8 @@ Trace events should use types as follows:
 Format strings should reflect the types defined in the trace event.  Take
 special care to use PRId64 and PRIu64 for int64_t and uint64_t types,
 respectively.  This ensures portability between 32- and 64-bit platforms.
+Format strings must not end with a newline character.  It is the responsibility
+of backends to adapt line ending for proper logging.
 
 Each event declaration will start with the event name, then its arguments,
 finally a format string for pretty-printing. For example:
diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
index 6fca674936..04279fa62e 100644
--- a/scripts/tracetool/__init__.py
+++ b/scripts/tracetool/__init__.py
@@ -277,6 +277,9 @@ class Event(object):
         if fmt.find("%m") != -1 or fmt_trans.find("%m") != -1:
             raise ValueError("Event format '%m' is forbidden, pass the error "
                              "as an explicit trace argument")
+        if fmt.endswith(r'\n"'):
+            raise ValueError("Event format must not end with a newline "
+                             "character")
 
         if len(fmt_trans) > 0:
             fmt = [fmt_trans, fmt]
-- 
2.20.1

Re: [Qemu-devel] [Qemu-block] [PATCH v2 0/2] trace: Forbid trailing newline in event format

[Stefan Hajnoczi]

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On Mon, Sep 16, 2019 at 11:51:19AM +0200, Philippe Mathieu-Daudé wrote:
> Hi Stefan,
> 
> I'v been confused by trailing newline in trace reports,
> so this series aims to fix this, by cleaning current
> formats and add a check to catch new one introduced.
> 
> v2:
> - Use regex format (easier to review)
> - Added R-b
> 
> Regards,
> 
> Phil.
> 
> Philippe Mathieu-Daudé (2):
>   trace: Remove trailing newline in events
>   trace: Forbid event format ending with newline character
> 
>  docs/devel/tracing.txt        |  2 ++
>  hw/misc/trace-events          | 10 +++++-----
>  hw/scsi/trace-events          |  2 +-
>  hw/sd/trace-events            |  2 +-
>  nbd/trace-events              |  4 ++--
>  net/trace-events              |  6 +++---
>  scripts/tracetool/__init__.py |  3 +++
>  7 files changed, 17 insertions(+), 12 deletions(-)

We can continue the broader discussion about whether trace events may
contain newlines in string arguments (John's AHCI case) or in
non-trailing position in the format string.  These patches look fine
though and are ready to go.

Thanks, applied (with Eric's typo fix) to my tracing tree:
https://github.com/stefanha/qemu/commits/tracing

Stefan

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