[DTrace-devel] [PATCH 4/7] Increase the maximum size of strstab

[Eugene Loh]

Reviewed-by: Eugene Loh <eugene.loh at oracle.com>

On 12/7/22 12:53, Kris Van Hees wrote:
> On Tue, Dec 06, 2022 at 05:14:36PM -0500, Eugene Loh via DTrace-devel wrote:
>> I do not understand this.  If the limit is SSIZE_MAX, then there is no point
>> in having a max (or a max check) at all.  The test (soff > DIF_STROFF_MAX)
>> can never fail.  So is the point to use a higher limit, or to remove the
>> limit entirely?
> I chose not to get rid of the define just yet because that entire set of
> defines needs to be reviewed and whatever is not needed, be dropped).  This
> patch gives us the minimal change to accomplish what we need.
>
> Also, there is value to this because the raw size of the strtab is actually
> much larger.  This define is a limit on the size of strtab we are able (or
> willing) to support in our programs.
>
>> On 12/6/22 16:50, Kris Van Hees via DTrace-devel wrote:
>>> The strtab size was limited in the legacy version to 0x7fff.  This
>>> was generally sufficient because of how the strtab was implemented.
>>> Now that all strings used in a probe program are stored in a single
>>> strtab (incl. probe description names), a higher limit is needed.
>>>
>>> All string offsets (and strtab size calculations) are using ssize_t,
>>> so we use SSIZE_MAX as the upper limit.
>>>
>>> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
>>> ---
>>>    include/dtrace/dif_defines.h | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/include/dtrace/dif_defines.h b/include/dtrace/dif_defines.h
>>> index 43824646..d88b3b2e 100644
>>> --- a/include/dtrace/dif_defines.h
>>> +++ b/include/dtrace/dif_defines.h
>>> @@ -113,7 +113,7 @@
>>>    #endif
>>>    #define	DIF_INTOFF_MAX		0xffff	/* highest integer table offset */
>>> -#define	DIF_STROFF_MAX		0x7fff	/* highest string table offset */
>>> +#define	DIF_STROFF_MAX		SSIZE_MAX /* highest string table offset */
>>>    #define	DIF_REGISTER_MAX	0xff	/* highest register number */
>>>    #define	DIF_VARIABLE_MAX	0xffff	/* highest variable identifier */
>>>    #define	DIF_SUBROUTINE_MAX	0xffff	/* highest subroutine code */
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