Add support for the link_ntop() subroutine

Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
Reviewed-by: Kris Van Hees <kris.van.hees@oracle.com>

bpf/Build

@@ -30,6 +30,7 @@ bpf_dlib_SOURCES = \
 	index.S \
 	inet_ntoa.S \
 	inet_ntoa6.S \
+	link_ntop.S \
 	lltostr.S \
 	mutex_owned.S \
 	mutex_owner.S \

bpf/link_ntop.S

@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ */
+
+#define BPF_FUNC_probe_read	4
+
+#define ARPHRD_ETHER		1	/* ARP protocol hw identifier <linux/if_arp.h> */
+#define ARPHRD_INFINIBAND	32	/* ARP protocol hw identifier <linux/if_arp.h> */
+
+#define ETH_ALEN		6	/* Octets in ethernet addr <linux/if_ether.h> */
+#define INFINIBAND_ALEN		20	/* Octets in IPoIB HW addr <linux/if_infiniband.h> */
+
+#define MAX_ALEN		20
+
+#define LENGTH			72
+
+	.text
+
+/*
+ * uint64_t write_byte2hex(const uint8_t src, char *dst)
+ */
+	.align	4
+	.global	write_byte2hex
+	.type	write_byte2hex, @function
+write_byte2hex:
+	/*
+	 * Branch-free implementation of byte-to-hex function.
+	 *
+	 * Process 4 bits (one hex digit) at a time.
+	 *
+	 * Given: r3 in [0, 15].
+	 * Then, ((-(r3 - 9)) >> 63) is 1 if r3 in [10, 15], and 0 otherwise.
+	 * Therefore, the hex digit (character) representing r3 is:
+	 *	r3 + '0' + ((-(r3 - 9)) >> 63) * ('a' - '0' - 10)
+	 */
+
+.macro WRITE_DIGIT n
+	/* Put digit n from %r1 into %r3. */
+	mov	%r3, %r1
+	rsh	%r3, 4 * (1 - \n)
+	and	%r3, 0xf
+
+	/* Store the converted value into %r2. */
+	mov	%r4, %r3
+	sub	%r4, 9
+	neg	%r4
+	rsh	%r4, 63
+	mul	%r4, 'a' - '0' - 10
+	add	%r4, '0'
+	add	%r4, %r3
+	stxb	[%r2 + \n], %r4
+.endm
+
+	WRITE_DIGIT 0
+	WRITE_DIGIT 1
+
+	exit
+	.size	write_byte2hex, .-write_byte2hex
+
+/*
+ * void link_ntop(const dt_dctx_t *dctx, const uint8_t *src, char *dst, uint32 type)
+ */
+	.align	4
+	.global	dt_link_ntop
+	.type	dt_link_ntop, @function
+dt_link_ntop:
+	/*
+	 * %r9		dst pointer
+	 * %r8		src copy
+	 * %r7		len left
+	 *
+	 * We copy the src string so that we can safely dereference individual
+	 * bytes.  The src string is at most MAX_ALEN bytes.  The dst string is
+	 * three times the src length.  The dst space is a tstring, which is
+	 * known to be at least 72 bytes.  This is long enough for both src copy
+	 * and dst string since, as we write the dst string, src bytes are
+	 * being used up.  So the dst string will start at byte 0 while src
+	 * will be copied to offset LENGTH-MAX_ALEN.
+	 */
+
+	/* Write pointer to dst. */
+	mov	%r9, %r3
+
+	/* Copy of src data. */
+	mov	%r8, %r3
+	add	%r8, LENGTH - MAX_ALEN
+
+	/* Store len in %r7 based on arg4. */
+	mov	%r7, ETH_ALEN
+	jeq	%r4, ARPHRD_INFINIBAND, .Lib
+	jne	%r4, ARPHRD_ETHER, .Lerror
+	ja	.Lcomp
+.Lib:
+	mov	%r7, INFINIBAND_ALEN
+.Lcomp:
+
+	/* Copy src data. */
+	mov	%r3, %r2
+	mov	%r2, %r7
+	mov	%r1, %r8
+	call	BPF_FUNC_probe_read
+	jne	%r0, 0, .Lerror
+
+	/* Loop over bytes.  Each byte is appended with a ':'. */
+.Lloop:
+	jle	%r7, 0, .Ldone
+	ldxb	%r1, [%r8 + 0]
+	mov	%r2, %r9
+	call	write_byte2hex
+	stb	[%r9 + 2], ':'
+	add	%r9, 3
+	add	%r8, 1
+	sub	%r7, 1
+	ja	.Lloop
+.Ldone:
+	stb	[%r9 + -1], 0
+	mov	%r0, 0
+	exit
+
+.Lerror:
+	/* Output the terminating NUL byte and return. */
+	stb	[%r9 + 0], 0
+	mov	%r0, 0
+	exit
+
+	.size	dt_link_ntop, .-dt_link_ntop

libdtrace/dt_cg.c

@@ -12,6 +12,9 @@
 #include <assert.h>
 #include <errno.h>
 
+#include <sys/socket.h>			/* needed for if_arp.h on OL7/x86 */
+#include <linux/if_arp.h>		/* ARPHRD_ETHER ARPHRD_INFINIBAND */
+
 #include <dt_impl.h>
 #include <dt_dis.h>
 #include <dt_dctx.h>
@@ -6239,6 +6242,25 @@ dt_cg_subr_inet_ntop(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
 	tnp->dn_tstring = NULL;
 }
 
+static void
+dt_cg_subr_link_ntop(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
+{
+	dt_node_t	*type = dnp->dn_args;
+	uint_t		Lokay = dt_irlist_label(dlp);
+
+	/* Determine type and check it is okay. */
+	dt_cg_node(type, dlp, drp);
+	emit(dlp,  BPF_BRANCH_IMM(BPF_JEQ, type->dn_reg, ARPHRD_INFINIBAND, Lokay));
+	emit(dlp,  BPF_BRANCH_IMM(BPF_JEQ, type->dn_reg, ARPHRD_ETHER, Lokay));
+	dt_cg_probe_error(yypcb, DTRACEFLT_ILLOP, DT_ISREG, type->dn_reg);
+	emitl(dlp, Lokay,
+		   BPF_NOP());
+
+	dt_cg_subr_arg_to_tstring(dnp, dlp, drp, "dt_link_ntop", 1,
+				  DT_ISREG, type->dn_reg, DT_IGNOR, 0);
+	dt_regset_free(drp, type->dn_reg);
+}
+
 typedef void dt_cg_subr_f(dt_node_t *, dt_irlist_t *, dt_regset_t *);
 
 static dt_cg_subr_f *_dt_cg_subr[DIF_SUBR_MAX + 1] = {
@@ -6287,7 +6309,7 @@ static dt_cg_subr_f *_dt_cg_subr[DIF_SUBR_MAX + 1] = {
 	[DIF_SUBR_INET_NTOA]		= &dt_cg_subr_inet_ntoa,
 	[DIF_SUBR_INET_NTOA6]		= &dt_cg_subr_inet_ntoa6,
 	[DIF_SUBR_D_PATH]		= NULL,
-	[DIF_SUBR_LINK_NTOP]		= NULL,
+	[DIF_SUBR_LINK_NTOP]		= &dt_cg_subr_link_ntop,
 };
 
 static void

test/unittest/funcs/err.link_ntopbadaddr.r

@@ -0,0 +1,3 @@
+-- @@stderr --
+dtrace: error on enabled probe ID 3 (ID 1: dtrace:::BEGIN): invalid address ({ptr}) in action #1 at BPF pc NNN
+

test/unittest/funcs/err.link_ntopbadarg.r

@@ -0,0 +1,3 @@
+-- @@stderr --
+dtrace: error on enabled probe ID 3 (ID 1: dtrace:::BEGIN): illegal operation in action #1 at BPF pc NNN
+

test/unittest/funcs/tst.link_ntop.d

@@ -4,7 +4,6 @@
  * Licensed under the Universal Permissive License v 1.0 as shown at
  * http://oss.oracle.com/licenses/upl.
  */
-/* @@xfail: dtv2 */
 
 #pragma D option quiet
 

test/unittest/funcs/tst.link_ntop_runtime_type.d

@@ -0,0 +1,85 @@
+/*
+ * Oracle Linux DTrace.
+ * Copyright (c) 2017, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Licensed under the Universal Permissive License v 1.0 as shown at
+ * http://oss.oracle.com/licenses/upl.
+ */
+
+#pragma D option quiet
+
+uint8_t ibaddr[20];
+
+BEGIN
+{
+	mytype = ARPHRD_ETHER;
+
+	this->buf_eth = (uint64_t *)alloca(sizeof(uint64_t));
+
+	/* Ethernet MAC address 00:01:02:03:04:05 */
+	*(this->buf_eth) = htonll(0x000102030405 << 16);
+	printf("%s\n", link_ntop(mytype, this->buf_eth));
+
+	/* Ethernet MAC address ff:ff:ff:ff:ff:ff */
+	*(this->buf_eth) = htonll(0xffffffffffff << 16);
+	printf("%s\n", link_ntop(mytype, this->buf_eth));
+
+	/* Ethernet MAC address 01:33:0a:00:00:01 */
+	*(this->buf_eth) = htonll(0x01330a000001 << 16);
+	printf("%s\n", link_ntop(mytype, this->buf_eth));
+
+	/* Ethernet MAC address 00:10:e0:8a:71:5e */
+	*(this->buf_eth) = htonll(0x0010e08a715e << 16);
+	printf("%s\n", link_ntop(mytype, this->buf_eth));
+
+	/* Ethernet MAC address 2:8:20:ac:4:e */
+	*(this->buf_eth) = htonll(0x020820ac040e << 16);
+	printf("%s\n", link_ntop(mytype, this->buf_eth));
+
+	mytype = ARPHRD_INFINIBAND;
+
+	ibaddr[0] = 0x10;
+	ibaddr[1] = 0x80;
+	ibaddr[2] = 0x08;
+	ibaddr[3] = 0x08;
+	ibaddr[4] = 0x20;
+	ibaddr[5] = 0x0c;
+	ibaddr[6] = 0x41;
+	ibaddr[7] = 0x7a;
+	ibaddr[8] = 0x01;
+	ibaddr[9] = 0x7f;
+	ibaddr[10] = 0x01;
+	ibaddr[11] = 0xff;
+	ibaddr[12] = 0xff;
+	ibaddr[13] = 0x7f;
+	ibaddr[14] = 0x01;
+	ibaddr[15] = 0xff;
+	ibaddr[16] = 0xfe;
+	ibaddr[17] = 0x7f;
+	ibaddr[18] = 0x01;
+	ibaddr[19] = 0xff;
+	printf("%s\n", link_ntop(mytype, ibaddr));
+
+	ibaddr[0] = 0x80;
+	ibaddr[1] = 0x00;
+	ibaddr[2] = 0x04;
+	ibaddr[3] = 0x04;
+	ibaddr[4] = 0xFE;
+	ibaddr[5] = 0x8C;
+	ibaddr[6] = 0x41;
+	ibaddr[7] = 0x7A;
+	ibaddr[8] = 0x00;
+	ibaddr[9] = 0x00;
+	ibaddr[10] = 0x00;
+	ibaddr[11] = 0x00;
+	ibaddr[12] = 0x00;
+	ibaddr[13] = 0x02;
+	ibaddr[14] = 0xC9;
+	ibaddr[15] = 0x02;
+	ibaddr[16] = 0x00;
+	ibaddr[17] = 0x29;
+	ibaddr[18] = 0x31;
+	ibaddr[19] = 0xCD;
+	printf("%s\n", link_ntop(mytype, ibaddr));
+
+	exit(0);
+}

test/unittest/funcs/tst.link_ntop_runtime_type.r

@@ -0,0 +1,8 @@
+00:01:02:03:04:05
+ff:ff:ff:ff:ff:ff
+01:33:0a:00:00:01
+00:10:e0:8a:71:5e
+02:08:20:ac:04:0e
+10:80:08:08:20:0c:41:7a:01:7f:01:ff:ff:7f:01:ff:fe:7f:01:ff
+80:00:04:04:fe:8c:41:7a:00:00:00:00:00:02:c9:02:00:29:31:cd
+