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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2025, Oracle and/or its affiliates.
*/
#include <bpf_asm_helpers.h>
#include <dtrace/faults_defines.h>
/*
* uint64_t dt_bvar_execargs(const dt_dctx_t *dctx, char *args)
*/
.text
.align 4
.global dt_bvar_execargs
.type dt_bvar_execargs, @function
dt_bvar_execargs:
stxdw [%fp+-8], %r1 /* save dctx to stack */
mov %r9, %r2 /* %r9 = args */
mov %r6, 0 /* set %r6 in case of error */
call BPF_FUNC_get_current_task /* get curthread (T) */
jeq %r0, 0, .Lerror
mov %r6, %r0
add %r6, TASK_MM /* %r6 = &(T->mm) */
mov %r1, %r9
mov %r2, 8
mov %r3, %r6
call BPF_FUNC_probe_read
jne %r0, 0, .Lerror
ldxdw %r8, [%r9+0] /* %r8 = T->mm */
jeq %r8, 0, .Lempty
mov %r6, %r8
add %r6, TASK_MM_ARG_START /* ptr = &(T->mm->arg_start) */
mov %r1, %r9
mov %r2, 8
mov %r3, %r6
call BPF_FUNC_probe_read
jne %r0, 0, .Lerror
ldxdw %r7, [%r9+0] /* %r7 = T->mm->arg_start */
mov %r6, %r8
add %r6, TASK_MM_ARG_END /* ptr = &(T->mm->arg_end) */
mov %r1, %r9
mov %r2, 8
mov %r3, %r6
call BPF_FUNC_probe_read
jne %r0, 0, .Lerror
ldxdw %r6, [%r9+0] /* %r6 = T->mm->arg_end */
mov %r8, %r6
sub %r8, %r7 /* %r8 = len = arg_end - arg_start */
jslt %r8, 2, .Lempty
mov %r0, STRSZ
jslt %r8, %r0, .Llen_ok
mov %r8, %r0
.Llen_ok:
/* read data from arg_start to arg_end */
mov %r1, %r9
mov %r2, %r8
mov %r3, %r7
call BPF_FUNC_probe_read_user /* bpf_probe_read_user(&args, len + 1, arg_start) */
jne %r0, 0, .Lerror
/* loop over args and replace '\0' with ' ' */
mov %r1, %r8
sub %r1, 2
.Lloop:
mov %r2, %r9
add %r2, %r1
ldxb %r0, [%r2+0]
jne %r0, 0, .Lnot_nil
stb [%r2+0], 32
.Lnot_nil:
sub %r1, 1
jsge %r1, 0, .Lloop
.Ldone:
mov %r0, %r9
exit /* return args */
.Lerror:
ldxdw %r1, [%fp+-8]
mov %r2, PC
mov %r3, DTRACEFLT_BADADDR
mov %r4, %r6
call dt_probe_error
.Lempty:
mov %r0, %r9
stb [%r9+0], 0 /* args[0] = 0 */
exit /* return args */
.size dt_bvar_execargs, .-dt_bvar_execargs
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