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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2023, 2024, Oracle and/or its affiliates.
*/
#include <bpf_asm_helpers.h>
#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
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