Date: Sun, 15 Sep 2013 18:16:23 -0400 From: Mark Johnston <markj@freebsd.org> To: dtrace-discuss@lists.dtrace.org Cc: freebsd-dtrace@freebsd.org Subject: pr_psargs on FreeBSD Message-ID: <20130915221622.GA2981@raichu>
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Hi!
One of the problems with FreeBSD's DTrace implementation is that it
doesn't have a good way of getting the arguments of a given process.
This is because of the way that they're stored, which is as a single
buffer with null-terminator between consecutive arguments. In
particular, there is no way within DTrace to convert such a buffer to a
single string (say by replacing all but the last terminator with
spaces). So scripts like execsnoop will only print the first element of
a process' argv on FreeBSD, which isn't particularly helpful for
interpreted programs.
You can get a fixed number of arguments with something like
printf("%s %s %s", cupsinfo->pr_psargs,
curpsinfo->pr_psargs + strlen(curpsinfo->pr_psargs) + 1,
curpsinfo->pr_psargs + strlen(curpsinfo->pr_psargs) + 1 +
strlen(curpsinfo->pr_psargs + strlen(curpsinfo->pr_psargs) + 1) + 1);
but this is less than ideal. :)
Apparently OS X has the same problem, but I don't have a machine to test
with, so I'm not completely sure.
It seems to me that there are two ways to solve this problem: change the
format that FreeBSD uses to store process arguments, or add a function
to DTrace which can convert the argument buffer to a string. I'm not too
keen on the former approach, so here's a proposal for the latter. It'd
be great to get some feedback on it and find out whether anyone thinks
it's a terrible idea. :)
It's kind of a strong-armed approach, but the problem's been around for a
while and I can't think of any clever solutions - I'd love to see an
alternative solution.
My patch against FreeBSD (pasted below) adds a function called memstr()
to DTrace. memstr() takes three arguments: addr, c, and len, and returns
a copy of addr of length len with all null-terminators replaced by c,
and with the last byte replaced by a null-terminator. In particular,
memstr() always returns a string of length len - 1, unless len == 0, in
which case we return the empty string.
With this function, the translator for the pr_psargs fields becomes
translator psinfo_t < struct proc *T > {
...
pr_psargs = memstr(T->p_args->ar_args, ' ', T->p_args->ar_length);
...
};
and execsnoop works properly. Any thoughts on this function? Have I missed
a better solution? A patch for FreeBSD is below.
Thanks,
-Mark
diff --git a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_open.c b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_open.c
index 9c9b2a6..83c81e5 100644
--- a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_open.c
+++ b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_open.c
@@ -122,8 +122,9 @@
#define DT_VERS_1_8_1 DT_VERSION_NUMBER(1, 8, 1)
#define DT_VERS_1_9 DT_VERSION_NUMBER(1, 9, 0)
#define DT_VERS_1_9_1 DT_VERSION_NUMBER(1, 9, 1)
-#define DT_VERS_LATEST DT_VERS_1_9_1
-#define DT_VERS_STRING "Sun D 1.9.1"
+#define DT_VERS_1_9_2 DT_VERSION_NUMBER(1, 9, 2)
+#define DT_VERS_LATEST DT_VERS_1_9_2
+#define DT_VERS_STRING "Sun D 1.9.2"
const dt_version_t _dtrace_versions[] = {
DT_VERS_1_0, /* D API 1.0.0 (PSARC 2001/466) Solaris 10 FCS */
@@ -145,6 +146,7 @@ const dt_version_t _dtrace_versions[] = {
DT_VERS_1_8_1, /* D API 1.8.1 */
DT_VERS_1_9, /* D API 1.9 */
DT_VERS_1_9_1, /* D API 1.9.1 */
+ DT_VERS_1_9_2, /* D API 1.9.2 */
0
};
@@ -311,6 +313,8 @@ static const dt_ident_t _dtrace_globals[] = {
&dt_idops_func, "void(@)" },
{ "memref", DT_IDENT_FUNC, 0, DIF_SUBR_MEMREF, DT_ATTR_STABCMN, DT_VERS_1_1,
&dt_idops_func, "uintptr_t *(void *, size_t)" },
+{ "memstr", DT_IDENT_FUNC, 0, DIF_SUBR_MEMSTR, DT_ATTR_STABCMN, DT_VERS_1_0,
+ &dt_idops_func, "string(void *, char, size_t)" },
{ "min", DT_IDENT_AGGFUNC, 0, DTRACEAGG_MIN, DT_ATTR_STABCMN, DT_VERS_1_0,
&dt_idops_func, "void(@)" },
{ "mod", DT_IDENT_ACTFUNC, 0, DT_ACT_MOD, DT_ATTR_STABCMN,
diff --git a/cddl/lib/libdtrace/psinfo.d b/cddl/lib/libdtrace/psinfo.d
index 068e72e..b2a009a 100644
--- a/cddl/lib/libdtrace/psinfo.d
+++ b/cddl/lib/libdtrace/psinfo.d
@@ -57,7 +57,7 @@ translator psinfo_t < struct proc *T > {
pr_gid = T->p_ucred->cr_rgid;
pr_egid = T->p_ucred->cr_groups[0];
pr_addr = 0;
- pr_psargs = stringof(T->p_args->ar_args);
+ pr_psargs = memstr(T->p_args->ar_args, ' ', T->p_args->ar_length);
pr_arglen = T->p_args->ar_length;
pr_jailid = T->p_ucred->cr_prison->pr_id;
};
diff --git a/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c b/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
index babc42c4..6d991fb 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
@@ -4920,6 +4920,38 @@ inetout: regs[rd] = (uintptr_t)end + 1;
break;
}
+ case DIF_SUBR_MEMSTR: {
+ char *str = (char *)mstate->dtms_scratch_ptr;
+ uintptr_t mem = tupregs[0].dttk_value;
+ char c = tupregs[1].dttk_value;
+ size_t size = tupregs[2].dttk_value;
+ uint8_t n;
+ int i;
+
+ regs[rd] = 0;
+
+ if (size == 0)
+ break;
+
+ if (!dtrace_canload(mem, size - 1, mstate, vstate))
+ break;
+
+ if (!DTRACE_INSCRATCH(mstate, size)) {
+ DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
+ break;
+ }
+
+ for (i = 0; i < size - 1; i++) {
+ n = dtrace_load8(mem++);
+ str[i] = (n == 0) ? c : n;
+ }
+ str[size - 1] = 0;
+
+ regs[rd] = (uintptr_t)str;
+ mstate->dtms_scratch_ptr += size;
+ break;
+ }
+
case DIF_SUBR_TYPEREF: {
uintptr_t size = 4 * sizeof(uintptr_t);
uintptr_t *typeref = (uintptr_t *) P2ROUNDUP(mstate->dtms_scratch_ptr, sizeof(uintptr_t));
@@ -9102,6 +9134,7 @@ dtrace_difo_validate_helper(dtrace_difo_t *dp)
subr == DIF_SUBR_NTOHL ||
subr == DIF_SUBR_NTOHLL ||
subr == DIF_SUBR_MEMREF ||
+ subr == DIF_SUBR_MEMSTR ||
subr == DIF_SUBR_TYPEREF)
break;
diff --git a/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h b/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
index 8728e30..295457c 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
+++ b/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
@@ -311,8 +311,9 @@ typedef enum dtrace_probespec {
#define DIF_SUBR_SX_SHARED_HELD 48
#define DIF_SUBR_SX_EXCLUSIVE_HELD 49
#define DIF_SUBR_SX_ISEXCLUSIVE 50
+#define DIF_SUBR_MEMSTR 51
-#define DIF_SUBR_MAX 50 /* max subroutine value */
+#define DIF_SUBR_MAX 51 /* max subroutine value */
typedef uint32_t dif_instr_t;
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