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Full Discussion: Data segment or Text segment
Top Forums Programming Data segment or Text segment Post 302519395 by Corona688 on Tuesday 3rd of May 2011 11:27:25 PM
Old 05-04-2011
Quote:
Originally Posted by shamrock
The rodata section is a specific section of the text segment set aside for storing constants and literals for the purpose of efficiency as they can be embedded in the instructions passed to the CPU and so no overhead is incurred to fetch them from memory.
Sorry, no. This contradicts itself on many levels. You don't embed something by separating it into its own, separate, independent segment -- that's the exact opposite of "embed". That it's not in the text segment indicates that it's not in the text segment.

It's definitely not a part of CPU instructions here either. There are CPU instructions that take a literal value, usually an integer or pointer of some sort, this isn't one of them. I'd believe that instructions can have embedded pointers to fixed strings, or might embed some data from the read-only section when it's of convenient sizes to fit in instruction literals, but the strings themselves are not embedded in the instructions, and therefore don't need to be embedded in the text segment.

Quote:
Another clue to the location of the literal is the fact that out of the 3 segments text data and stack only the text segment is readonly
This logic only works if you assume that only text segments are read-only. This is not true.

This isn't to say there aren't architectures where strings might be embedded in the text segment for some reason, but this isn't one of them.

Last edited by Corona688; 05-04-2011 at 12:32 AM..
 

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plock(3C)						   Standard C Library Functions 						 plock(3C)

NAME
plock - lock or unlock into memory process, text, or data SYNOPSIS
#include <sys/lock.h> int plock(int op); DESCRIPTION
The plock() function allows the calling process to lock or unlock into memory its text segment (text lock), its data segment (data lock), or both its text and data segments (process lock). Locked segments are immune to all routine swapping. The effective user ID of the calling process must be super-user to use this call. The plock() function performs the function specified by op: PROCLOCK Lock text and data segments into memory (process lock). TXTLOCK Lock text segment into memory (text lock). DATLOCK Lock data segment into memory (data lock). UNLOCK Remove locks. RETURN VALUES
Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error. ERRORS
The plock() function fails and does not perform the requested operation if: EAGAIN Not enough memory. EINVAL The op argument is equal to PROCLOCK and a process lock, a text lock, or a data lock already exists on the calling process; the op argument is equal to TXTLOCK and a text lock or a process lock already exists on the calling process; the op argument is equal to DATLOCK and a data lock or a process lock already exists on the calling process; or the op argument is equal to UNLOCK and no lock exists on the calling process. EPERM The {PRIV_PROC_LOCK_MEMORY} privilege is not asserted in the effective set of the calling process. USAGE
The mlock(3C) and mlockall(3C) functions are the preferred interfaces for process locking. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
exec(2), exit(2), fork(2), memcntl(2), mlock(3C), mlockall(3C), attributes(5) SunOS 5.10 22 Mar 2004 plock(3C)
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