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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2021, 2024, Oracle and/or its affiliates.
*/
#include <bpf_asm_helpers.h>
/*
* void dt_dirname(const dt_dctx_t *dctx, char *src, char *dst);
*/
.text
.align 4
.global dt_dirname
.type dt_dirname, @function
dt_dirname :
#define SRC %r6
#define DST %r7
#define LEN %r8
/* store copies of input arguments */
mov SRC, %r2
mov DST, %r3
/*
* Copy src to dst for two reasons:
* - to get the string length
* - to have a copy that we can access directly
*/
/* r0 = bpf_probe_read_str(dst, STRSZ + 1, src) */
mov %r1, DST
lddw %r2, STRSZ
add %r2, 1
mov %r3, SRC
call BPF_FUNC_probe_read_str
/* if (r0 s<= 1) goto Ldot */
jsle %r0, 1, .Ldot
/* len = r0 - 1 */
mov LEN, %r0
sub LEN, 1
/*
* In general, the string will look like
* "dirname////basename////".
*/
/*
* Back up, looking for a non-'/' char.
* That gives us the end of basename.
*/
.L1:
/* len-- */
sub LEN, 1
/* if (len s< 0) goto Lslash */
jslt LEN, 0, .Lslash
/* if (dst[len] == '/') goto L1 */
mov %r0, DST
add %r0, LEN
ldxb %r0, [%r0+0]
and %r0, 0xff
jeq %r0, '/', .L1
/*
* Back up, looking for a '/' char.
* That gives us right before the start of basename.
*/
.L2:
/* len-- */
sub LEN, 1
/* if (len s< 0) goto Ldot */
jslt LEN, 0, .Ldot
/* if (dst[len] != '/') goto L2 */
mov %r0, DST
add %r0, LEN
ldxb %r0, [%r0+0]
and %r0, 0xff
jne %r0, '/', .L2
/*
* Back up, looking for a non-'/' char.
* That gives us the end of dirname.
*/
.L3:
/* len-- */
sub LEN, 1
/* if (len s< 0) goto Lslash */
jslt LEN, 0, .Lslash
/* if (dst[len] == '/') goto L3 */
mov %r0, DST
add %r0, LEN
ldxb %r0, [%r0+0]
and %r0, 0xff
jeq %r0, '/', .L3
/* len++ */
add LEN, 1
/*
* The output string is up to the end of the dirname.
*/
/* bpf_probe_read_str(dst, len + 1, src) */
mov %r1, DST
mov %r2, LEN
add %r2, 1
mov %r3, SRC
call BPF_FUNC_probe_read_str
/* return */
exit
.Ldot:
/*
* The output string is simply ".".
*/
mov LEN, 1
stb [DST+0], '.'
stb [DST+1], 0
exit
.Lslash:
/*
* The output string is simply "/".
*/
mov LEN, 1
stb [DST+0], '/'
stb [DST+1], 0
exit
#undef SRC
#undef DST
#undef LEN
.size dt_dirname, .-dt_dirname
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