* [PATCH] Fix traceaio with IO_CMD_{PREAD,PWRITE}
@ 2021-09-23 17:49 Nir Soffer
2021-09-23 22:21 ` Nir Soffer
0 siblings, 1 reply; 4+ messages in thread
From: Nir Soffer @ 2021-09-23 17:49 UTC (permalink / raw)
To: systemtap; +Cc: teigland, fche, Nir Soffer
When using IO_CMD_{PREAD,PWRITE} aio_nbytes is the size of a single
buffer aio_buf.
Previously the script logged unrelated memory contents from userspace:
[ 0 sanlock(8214):] io_submit(140589225578496, 1, 0x7fdd5fefc718)
iocb[ 0]=0x7fdd58000b70, fd=16, opcode=0, offset=0, nbytes=1048576, buf=0x7fdd5c5f6000
iovec[ 0]=0x7fdd5c5f6000, base=0x3000412212010, len=16
iovec[ 1]=0x7fdd5c5f6010, base=0x0, len=1
iovec[ 2]=0x7fdd5c5f6020, base=0x1, len=16
...
Now we trace iovecs only when using IO_CMD_{PREADV,PWITEV}:
[ 0 sanlock(8397):] io_submit(140589225566208, 1, 0x7fdd5e6f9718)
iocb[ 0]=0x7fdd48000b70, fd=19, opcode=0, offset=0, nbytes=1048576, buf=0x7fdd5c3f2000
[ 0 sanlock(8397):] io_submit(140589225566208, 1, 0x7fdd5e6f9718)
iocb[ 0]=0x7fdd48000b70, fd=19, opcode=1, offset=512, nbytes=512, buf=0x7fdd4810a000
Signed-off-by: Nir Soffer <nsoffer@redhat.com>
---
testsuite/systemtap.examples/io/traceaio.stp | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/testsuite/systemtap.examples/io/traceaio.stp b/testsuite/systemtap.examples/io/traceaio.stp
index 126ea9c3c..903d65526 100755
--- a/testsuite/systemtap.examples/io/traceaio.stp
+++ b/testsuite/systemtap.examples/io/traceaio.stp
@@ -8,6 +8,9 @@
# published by the Free Software Foundation.
#
+@define IO_CMD_PREADV %( 7 %)
+@define IO_CMD_PWRITEV %( 8 %)
+
probe begin {
println("Tracing started");
}
@@ -27,12 +30,14 @@ probe syscall.io_submit
printf(" iocb[%4d]=%p, fd=%d, opcode=%d, offset=%d, nbytes=%d, buf=%p\n",
i, iocbp, fd, opcode, offset, nbytes, buf)
- for (j = 0; j < nbytes; j++) {
- iovecp = &@cast(buf, "iovec", "kernel")[j]
- base = user_uint64(&@cast(iovecp, "iovec", "kernel")->iov_base)
- len = user_uint32(&@cast(iovecp, "iovec", "kernel")->iov_len)
- printf(" iovec[%4d]=%p, base=%p, len=%d\n",
- j, iovecp, base, len)
+ if (opcode == @IO_CMD_PREADV || opcode == @IO_CMD_PREADV) {
+ for (j = 0; j < nbytes; j++) {
+ iovecp = &@cast(buf, "iovec", "kernel")[j]
+ base = user_uint64(&@cast(iovecp, "iovec", "kernel")->iov_base)
+ len = user_uint32(&@cast(iovecp, "iovec", "kernel")->iov_len)
+ printf(" iovec[%4d]=%p, base=%p, len=%d\n",
+ j, iovecp, base, len)
+ }
}
}
}
--
2.31.1
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] Fix traceaio with IO_CMD_{PREAD,PWRITE}
2021-09-23 17:49 [PATCH] Fix traceaio with IO_CMD_{PREAD,PWRITE} Nir Soffer
@ 2021-09-23 22:21 ` Nir Soffer
2021-09-23 23:00 ` Frank Ch. Eigler
0 siblings, 1 reply; 4+ messages in thread
From: Nir Soffer @ 2021-09-23 22:21 UTC (permalink / raw)
To: systemtap; +Cc: David Teigland, fche
On Thu, Sep 23, 2021 at 8:49 PM Nir Soffer <nsoffer@redhat.com> wrote:
>
> When using IO_CMD_{PREAD,PWRITE} aio_nbytes is the size of a single
> buffer aio_buf.
>
> Previously the script logged unrelated memory contents from userspace:
>
> [ 0 sanlock(8214):] io_submit(140589225578496, 1, 0x7fdd5fefc718)
> iocb[ 0]=0x7fdd58000b70, fd=16, opcode=0, offset=0, nbytes=1048576, buf=0x7fdd5c5f6000
> iovec[ 0]=0x7fdd5c5f6000, base=0x3000412212010, len=16
> iovec[ 1]=0x7fdd5c5f6010, base=0x0, len=1
> iovec[ 2]=0x7fdd5c5f6020, base=0x1, len=16
> ...
>
> Now we trace iovecs only when using IO_CMD_{PREADV,PWITEV}:
>
> [ 0 sanlock(8397):] io_submit(140589225566208, 1, 0x7fdd5e6f9718)
> iocb[ 0]=0x7fdd48000b70, fd=19, opcode=0, offset=0, nbytes=1048576, buf=0x7fdd5c3f2000
> [ 0 sanlock(8397):] io_submit(140589225566208, 1, 0x7fdd5e6f9718)
> iocb[ 0]=0x7fdd48000b70, fd=19, opcode=1, offset=512, nbytes=512, buf=0x7fdd4810a000
>
> Signed-off-by: Nir Soffer <nsoffer@redhat.com>
> ---
> testsuite/systemtap.examples/io/traceaio.stp | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/testsuite/systemtap.examples/io/traceaio.stp b/testsuite/systemtap.examples/io/traceaio.stp
> index 126ea9c3c..903d65526 100755
> --- a/testsuite/systemtap.examples/io/traceaio.stp
> +++ b/testsuite/systemtap.examples/io/traceaio.stp
> @@ -8,6 +8,9 @@
> # published by the Free Software Foundation.
> #
>
> +@define IO_CMD_PREADV %( 7 %)
> +@define IO_CMD_PWRITEV %( 8 %)
Unfortunately this does not work. I tested this before adding these "constants".
This works:
global IO_CMD_PREADV = 7
global IO_CMD_PWRITEV = 8
Do we have a better way to handle this?
> +
> probe begin {
> println("Tracing started");
> }
> @@ -27,12 +30,14 @@ probe syscall.io_submit
> printf(" iocb[%4d]=%p, fd=%d, opcode=%d, offset=%d, nbytes=%d, buf=%p\n",
> i, iocbp, fd, opcode, offset, nbytes, buf)
>
> - for (j = 0; j < nbytes; j++) {
> - iovecp = &@cast(buf, "iovec", "kernel")[j]
> - base = user_uint64(&@cast(iovecp, "iovec", "kernel")->iov_base)
> - len = user_uint32(&@cast(iovecp, "iovec", "kernel")->iov_len)
> - printf(" iovec[%4d]=%p, base=%p, len=%d\n",
> - j, iovecp, base, len)
> + if (opcode == @IO_CMD_PREADV || opcode == @IO_CMD_PREADV) {
> + for (j = 0; j < nbytes; j++) {
> + iovecp = &@cast(buf, "iovec", "kernel")[j]
> + base = user_uint64(&@cast(iovecp, "iovec", "kernel")->iov_base)
> + len = user_uint32(&@cast(iovecp, "iovec", "kernel")->iov_len)
> + printf(" iovec[%4d]=%p, base=%p, len=%d\n",
> + j, iovecp, base, len)
> + }
> }
> }
> }
> --
> 2.31.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] Fix traceaio with IO_CMD_{PREAD,PWRITE}
2021-09-23 22:21 ` Nir Soffer
@ 2021-09-23 23:00 ` Frank Ch. Eigler
2021-09-29 9:14 ` Nir Soffer
0 siblings, 1 reply; 4+ messages in thread
From: Frank Ch. Eigler @ 2021-09-23 23:00 UTC (permalink / raw)
To: Nir Soffer; +Cc: systemtap, David Teigland
Hi -
> This works:
>
> global IO_CMD_PREADV = 7
> global IO_CMD_PWRITEV = 8
>
> Do we have a better way to handle this?
Within a tapset snippet, code can use
@const("IO_CMD_PREADV")
referring to an identifier in embedded-C scope.
If the IO_CMD_PREADV identifier were an enum value that shows up in
DWARF, then $IO_CMD_PREADV can resolve in recent versions of stap.
If none of the above, yeah, use the global gadget.
- FChE
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] Fix traceaio with IO_CMD_{PREAD,PWRITE}
2021-09-23 23:00 ` Frank Ch. Eigler
@ 2021-09-29 9:14 ` Nir Soffer
0 siblings, 0 replies; 4+ messages in thread
From: Nir Soffer @ 2021-09-29 9:14 UTC (permalink / raw)
To: Frank Ch. Eigler; +Cc: systemtap, David Teigland
On Fri, Sep 24, 2021 at 2:00 AM Frank Ch. Eigler <fche@redhat.com> wrote:
>
> Hi -
>
> > This works:
> >
> > global IO_CMD_PREADV = 7
> > global IO_CMD_PWRITEV = 8
> >
> > Do we have a better way to handle this?
>
> Within a tapset snippet, code can use
> @const("IO_CMD_PREADV")
> referring to an identifier in embedded-C scope.
This works, bug require -g in stap script. I don't think it makes sense
to require Guru mode just to access an enum. It would be nice it this
could work without -g, since accessing constants seems to be a safe
operation.
> If the IO_CMD_PREADV identifier were an enum value that shows up in
> DWARF, then $IO_CMD_PREADV can resolve in recent versions of stap.
I could not find the enum in debuginfo files or in stap -L output, but maybe
I was not using the right tool for this.
In a test program using libaio, I cannot find the enum values in the symbols
so I guess this info is not available.
> If none of the above, yeah, use the global gadget.
I sent v2 using globals.
Nir
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-09-23 17:49 [PATCH] Fix traceaio with IO_CMD_{PREAD,PWRITE} Nir Soffer
2021-09-23 22:21 ` Nir Soffer
2021-09-23 23:00 ` Frank Ch. Eigler
2021-09-29 9:14 ` Nir Soffer
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