[DTrace-devel] [PATCH 06/14] Support strrchr() for addresses that are not DTrace pointers

[Kris Van Hees]

On Thu, Nov 03, 2022 at 03:52:18PM -0400, eugene.loh--- via DTrace-devel wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
> 
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>

Reviewed-by: Kris Van Hees <kris.van.hees at oracle.com>

> ---
>  bpf/strrchr.S                            |  6 +++---
>  test/unittest/funcs/tst.strchr_nonDPTR.d | 25 ++++++++++++++++++++++++
>  test/unittest/funcs/tst.strchr_nonDPTR.r |  3 +++
>  3 files changed, 31 insertions(+), 3 deletions(-)
>  create mode 100644 test/unittest/funcs/tst.strchr_nonDPTR.d
>  create mode 100644 test/unittest/funcs/tst.strchr_nonDPTR.r
> 
> diff --git a/bpf/strrchr.S b/bpf/strrchr.S
> index 8273b59c..05ccecb9 100644
> --- a/bpf/strrchr.S
> +++ b/bpf/strrchr.S
> @@ -21,7 +21,7 @@
>   *     r8 = r6;
>   * Lloop:
>   *     r8--;
> - *     r3 = src[r8];
> + *     r3 = dst[r8];     // use copy in dst[] in case src[] is unsafe memory
>   *     r3 <<= 56;
>   *     if (r3 == c) goto Lfound;
>   *     if (r8 > 0) goto Lloop;
> @@ -65,9 +65,9 @@ dt_strrchr :
>  .Lloop:
>  	sub	%r8, 1			/* r8-- */
>  	mov	%r4, %r8
> -	ldxdw	%r3, [%fp+-8]
> +	ldxdw	%r3, [%fp+-24]
>  	add	%r3, %r4
> -	ldxb	%r3, [%r3+0]		/* r3 = src[r8] */
> +	ldxb	%r3, [%r3+0]		/* r3 = dst[r8] */
>  	lsh	%r3, 56			/* r3 <<= 56 */
>  	jeq	%r3, %r5, .Lfound	/* if (r3 == c) goto Lfound */
>  	jgt	%r8, 0, .Lloop		/* if (r8 > 0) goto Lloop */
> diff --git a/test/unittest/funcs/tst.strchr_nonDPTR.d b/test/unittest/funcs/tst.strchr_nonDPTR.d
> new file mode 100644
> index 00000000..95cb08c2
> --- /dev/null
> +++ b/test/unittest/funcs/tst.strchr_nonDPTR.d
> @@ -0,0 +1,25 @@
> +/*
> + * Oracle Linux DTrace.
> + * Copyright (c) 2022, 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
> +#pragma D option destructive
> +
> +BEGIN
> +{
> +	/* "abcdef" */
> +	system("printf '\x61\x62\x63\x64\x65\x66' > /dev/null 2>&1");
> +}
> +
> +syscall::write:entry
> +/ppid == $pid/
> +{
> +	printf("|%s|\n", strchr((void *)arg1, 'b'));
> +	printf("|%s|\n", strrchr((void *)arg1, 'b'));
> +	exit(0);
> +}
> +
> +ERROR { exit(1); }
> diff --git a/test/unittest/funcs/tst.strchr_nonDPTR.r b/test/unittest/funcs/tst.strchr_nonDPTR.r
> new file mode 100644
> index 00000000..b1b10def
> --- /dev/null
> +++ b/test/unittest/funcs/tst.strchr_nonDPTR.r
> @@ -0,0 +1,3 @@
> +|bcdef|
> +|bcdef|
> +
> -- 
> 2.18.4
> 
> 
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