Re: [DTrace-devel] [PATCH 5/5] string: ensure string size is handled correctly

Kris Van Hees <[email protected]>
Newsgroups dev.linux.lists.dtrace
Message-ID <[email protected]> 
A v2 coming soon - I needed to cover a few more cases of tests that I failed to
notice.

On Wed, Aug 13, 2025 at 11:57:33AM -0400, Kris Van Hees via DTrace-devel wrote:
> A string is defined as a character array of size strsize.  Strings
> that are less that strsize in length are terminated by a NUL byte.
> This implies that the NUL byte is part of the array and therefore,
> strsuze is indeed the size of the array and not the maximum number
> of characters in the string.
> 
> Tests are adjusted to reflect this behaviour.
> 
> Signed-off-by: Kris Van Hees <[email protected]>
> ---
>  libdtrace/dt_cg.c                                     | 11 +++++------
>  .../funcs/inet_ntoa6/tst.inet_ntoa6.strsize_10.r      |  6 +++---
>  test/unittest/funcs/strjoin/tst.strjoin-bordercases.d |  2 +-
>  .../funcs/strjoin/tst.strjoin-capped-size-2.d         |  2 +-
>  .../funcs/strjoin/tst.strjoin-capped-size-3.d         |  2 +-
>  test/unittest/funcs/strjoin/tst.strjoin-capped-size.d |  2 +-
>  test/unittest/funcs/strjoin/tst.strjoin_nonDPTR.d     |  2 +-
>  test/unittest/funcs/strtok/tst.strtok_long.d          |  4 ++--
>  test/unittest/funcs/strtok/tst.strtok_long.r          |  4 ++--
>  test/unittest/funcs/substr/tst.substr-stored-len.d    |  2 +-
>  test/unittest/funcs/substr/tst.substr-strsize.d       |  2 +-
>  test/unittest/funcs/substr/tst.substr_nonDPTR.d       |  2 +-
>  test/unittest/funcs/tst.basename_nonDPTR.d            |  2 +-
>  test/unittest/funcs/tst.inet_ntoa_nonDPTR.d           |  2 +-
>  test/unittest/funcs/tst.lltostr-short.d               |  2 +-
>  15 files changed, 23 insertions(+), 24 deletions(-)
> 
> diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
> index 88dddb087..cd9e7f4e9 100644
> --- a/libdtrace/dt_cg.c
> +++ b/libdtrace/dt_cg.c
> @@ -1741,11 +1741,10 @@ dt_cg_store_val(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind,
>  			dt_cg_check_ptr_arg(dlp, drp, dnp, NULL);
>  
>  		TRACE_REGSET("store_val(): Begin ");
> -		off = dt_rec_add(dtp, dt_cg_fill_gap, kind, size + 1, 1, pfp,
> -				 arg);
> +		off = dt_rec_add(dtp, dt_cg_fill_gap, kind, size, 1, pfp, arg);
>  
>  		/*
> -		 * Copy the string data (no more than STRSIZE + 1 bytes) to the
> +		 * Copy the string data (no more than STRSIZE bytes) to the
>  		 * buffer at (%r9 + off).  We depend on the fact that
>  		 * probe_read_str() stops at the terminating NUL byte.
>  		 */
> @@ -1754,7 +1753,7 @@ dt_cg_store_val(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind,
>  
>  		emit(dlp, BPF_MOV_REG(BPF_REG_1, BPF_REG_9));
>  		emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, off));
> -		emit(dlp, BPF_MOV_IMM(BPF_REG_2, strsize + 1));
> +		emit(dlp, BPF_MOV_IMM(BPF_REG_2, strsize));
>  		emit(dlp, BPF_MOV_REG(BPF_REG_3, dnp->dn_reg));
>  		dt_regset_free(drp, dnp->dn_reg);
>  		dt_cg_tstring_free(pcb, dnp);
> @@ -1765,13 +1764,13 @@ dt_cg_store_val(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind,
>  		/*
>  		 * Pad the rest with zeroes, if necessary.
>  		 */
> -		emit(dlp,  BPF_BRANCH_IMM(BPF_JGE, BPF_REG_0, strsize + 1, lbl_ok));
> +		emit(dlp,  BPF_BRANCH_IMM(BPF_JGE, BPF_REG_0, strsize, lbl_ok));
>  		if (dt_regset_xalloc_args(drp) == -1)
>  			longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
>  		emit(dlp,  BPF_MOV_REG(BPF_REG_1, BPF_REG_9));
>  		emit(dlp,  BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, off));
>  		emit(dlp,  BPF_ALU64_REG(BPF_ADD, BPF_REG_1, BPF_REG_0));
> -		emit(dlp,  BPF_MOV_IMM(BPF_REG_2, strsize + 1));
> +		emit(dlp,  BPF_MOV_IMM(BPF_REG_2, strsize));
>  		emit(dlp,  BPF_ALU64_REG(BPF_SUB, BPF_REG_2, BPF_REG_0));
>  		dt_cg_zerosptr(BPF_REG_3, dlp, drp);
>  		emit(dlp,  BPF_CALL_HELPER(dtp->dt_bpfhelper[BPF_FUNC_probe_read_kernel]));
> diff --git a/test/unittest/funcs/inet_ntoa6/tst.inet_ntoa6.strsize_10.r b/test/unittest/funcs/inet_ntoa6/tst.inet_ntoa6.strsize_10.r
> index 5e7d49b03..8090daad6 100644
> --- a/test/unittest/funcs/inet_ntoa6/tst.inet_ntoa6.strsize_10.r
> +++ b/test/unittest/funcs/inet_ntoa6/tst.inet_ntoa6.strsize_10.r
> @@ -1,8 +1,8 @@
> -fe80:7060:
> -1080::808:
> +fe80:7060
> +1080::808
>  ::1
>  ::
>  127.0.0.1
>  127.0.0.1
> -::fffe:7f0
> +::fffe:7f
>  
> diff --git a/test/unittest/funcs/strjoin/tst.strjoin-bordercases.d b/test/unittest/funcs/strjoin/tst.strjoin-bordercases.d
> index 253b2d6ef..1ac5ffd12 100644
> --- a/test/unittest/funcs/strjoin/tst.strjoin-bordercases.d
> +++ b/test/unittest/funcs/strjoin/tst.strjoin-bordercases.d
> @@ -6,7 +6,7 @@
>   */
>  
>  #pragma D option rawbytes
> -#pragma D option strsize=5
> +#pragma D option strsize=6
>  #pragma D option quiet
>  
>  BEGIN
> diff --git a/test/unittest/funcs/strjoin/tst.strjoin-capped-size-2.d b/test/unittest/funcs/strjoin/tst.strjoin-capped-size-2.d
> index 625c786b6..44a6acd88 100644
> --- a/test/unittest/funcs/strjoin/tst.strjoin-capped-size-2.d
> +++ b/test/unittest/funcs/strjoin/tst.strjoin-capped-size-2.d
> @@ -6,7 +6,7 @@
>   */
>  
>  #pragma D option rawbytes
> -#pragma D option strsize=6
> +#pragma D option strsize=7
>  #pragma D option quiet
>  
>  BEGIN
> diff --git a/test/unittest/funcs/strjoin/tst.strjoin-capped-size-3.d b/test/unittest/funcs/strjoin/tst.strjoin-capped-size-3.d
> index 52718325a..d2982a70b 100644
> --- a/test/unittest/funcs/strjoin/tst.strjoin-capped-size-3.d
> +++ b/test/unittest/funcs/strjoin/tst.strjoin-capped-size-3.d
> @@ -6,7 +6,7 @@
>   */
>  
>  #pragma D option rawbytes
> -#pragma D option strsize=6
> +#pragma D option strsize=7
>  #pragma D option quiet
>  
>  BEGIN
> diff --git a/test/unittest/funcs/strjoin/tst.strjoin-capped-size.d b/test/unittest/funcs/strjoin/tst.strjoin-capped-size.d
> index fe5b323f7..b54fd2f29 100644
> --- a/test/unittest/funcs/strjoin/tst.strjoin-capped-size.d
> +++ b/test/unittest/funcs/strjoin/tst.strjoin-capped-size.d
> @@ -6,7 +6,7 @@
>   */
>  
>  #pragma D option rawbytes
> -#pragma D option strsize=10
> +#pragma D option strsize=11
>  #pragma D option quiet
>  
>  BEGIN
> diff --git a/test/unittest/funcs/strjoin/tst.strjoin_nonDPTR.d b/test/unittest/funcs/strjoin/tst.strjoin_nonDPTR.d
> index a1816f975..2b700a5a8 100644
> --- a/test/unittest/funcs/strjoin/tst.strjoin_nonDPTR.d
> +++ b/test/unittest/funcs/strjoin/tst.strjoin_nonDPTR.d
> @@ -6,7 +6,7 @@
>   */
>  
>  #pragma D option quiet
> -#pragma D option strsize=14
> +#pragma D option strsize=15
>  
>  BEGIN
>  {
> diff --git a/test/unittest/funcs/strtok/tst.strtok_long.d b/test/unittest/funcs/strtok/tst.strtok_long.d
> index 1fbe415dc..254a65485 100644
> --- a/test/unittest/funcs/strtok/tst.strtok_long.d
> +++ b/test/unittest/funcs/strtok/tst.strtok_long.d
> @@ -9,8 +9,8 @@
>  
>  BEGIN
>  {
> -	/* 256-char string ending in "XYZ" */
> -	x = "_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________XYZ";
> +	/* 256-char string ending in "XYZ" (255 chars + NUL byte)*/
> +	x = "____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________XYZ";
>  
>  	/* check whether the last char of a long string is seen */
>  	y = "a";
> diff --git a/test/unittest/funcs/strtok/tst.strtok_long.r b/test/unittest/funcs/strtok/tst.strtok_long.r
> index a752554e8..4b172ca1b 100644
> --- a/test/unittest/funcs/strtok/tst.strtok_long.r
> +++ b/test/unittest/funcs/strtok/tst.strtok_long.r
> @@ -1,5 +1,5 @@
> -_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________XYZ
> +____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________XYZ
>  zyxwvutsrqponmlkjihgfedcba
> -_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________XY
> +____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________XY
>  Z
>  
> diff --git a/test/unittest/funcs/substr/tst.substr-stored-len.d b/test/unittest/funcs/substr/tst.substr-stored-len.d
> index 97d2b0f61..fa3e5337c 100644
> --- a/test/unittest/funcs/substr/tst.substr-stored-len.d
> +++ b/test/unittest/funcs/substr/tst.substr-stored-len.d
> @@ -13,7 +13,7 @@
>  
>  #pragma D option quiet
>  #pragma D option rawbytes
> -#pragma D option strsize=13
> +#pragma D option strsize=14
>  
>  BEGIN
>  {
> diff --git a/test/unittest/funcs/substr/tst.substr-strsize.d b/test/unittest/funcs/substr/tst.substr-strsize.d
> index b4d0cc63e..04eab4297 100644
> --- a/test/unittest/funcs/substr/tst.substr-strsize.d
> +++ b/test/unittest/funcs/substr/tst.substr-strsize.d
> @@ -15,7 +15,7 @@
>  
>  #pragma D option quiet
>  #pragma D option rawbytes
> -#pragma D option strsize=13
> +#pragma D option strsize=14
>  
>  BEGIN
>  {
> diff --git a/test/unittest/funcs/substr/tst.substr_nonDPTR.d b/test/unittest/funcs/substr/tst.substr_nonDPTR.d
> index 9d847ab6f..3e10af08e 100644
> --- a/test/unittest/funcs/substr/tst.substr_nonDPTR.d
> +++ b/test/unittest/funcs/substr/tst.substr_nonDPTR.d
> @@ -6,7 +6,7 @@
>   */
>  
>  #pragma D option quiet
> -#pragma D option strsize=13
> +#pragma D option strsize=14
>  
>  BEGIN
>  {
> diff --git a/test/unittest/funcs/tst.basename_nonDPTR.d b/test/unittest/funcs/tst.basename_nonDPTR.d
> index 4f93685f7..cecef827b 100644
> --- a/test/unittest/funcs/tst.basename_nonDPTR.d
> +++ b/test/unittest/funcs/tst.basename_nonDPTR.d
> @@ -6,7 +6,7 @@
>   */
>  
>  #pragma D option quiet
> -#pragma D option strsize=14
> +#pragma D option strsize=15
>  
>  BEGIN
>  {
> diff --git a/test/unittest/funcs/tst.inet_ntoa_nonDPTR.d b/test/unittest/funcs/tst.inet_ntoa_nonDPTR.d
> index 500c53e86..f079c7ef4 100644
> --- a/test/unittest/funcs/tst.inet_ntoa_nonDPTR.d
> +++ b/test/unittest/funcs/tst.inet_ntoa_nonDPTR.d
> @@ -6,7 +6,7 @@
>   */
>  
>  #pragma D option quiet
> -#pragma D option strsize=14
> +#pragma D option strsize=15
>  
>  BEGIN
>  {
> diff --git a/test/unittest/funcs/tst.lltostr-short.d b/test/unittest/funcs/tst.lltostr-short.d
> index 969045667..65a5714c2 100644
> --- a/test/unittest/funcs/tst.lltostr-short.d
> +++ b/test/unittest/funcs/tst.lltostr-short.d
> @@ -6,7 +6,7 @@
>   */
>  
>  #pragma D option quiet
> -#pragma D option strsize=7
> +#pragma D option strsize=8
>  
>  BEGIN
>  {
> -- 
> 2.45.2
> 
> 
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