Re: port-sparc/60838: sparc fails to enforce RLIMIT_DATA on exec

["Taylor R Campbell via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR port-sparc/60838; it has been noted by GNATS.

From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
To: gnats-bugs%NetBSD.org@localhost, netbsd-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: port-sparc/60838: sparc fails to enforce RLIMIT_DATA on exec
Date: Fri, 2 Oct 2026 16:43:03 +0000

 Looks like the kernel might consider the executable in question to
 have zero data size because all LOAD segments have the X bit set
 (/bin/sh, but I also checked a couple others, /bin/ls, /bin/sync, and
 /usr/bin/awk on sparc64, and they have the same pattern):
 
 $ readelf -l ./bin/sh
 ...
   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
 ...
   LOAD           0x000000 0x00010000 0x00010000 0x30760 0x30760 R E 0x10000
   LOAD           0x030760 0x00050760 0x00050760 0x00af4 0x02468 RWE 0x10000
 
 (Here `E' means execute, which I'm also calling `X' because the
 constant is named PF_X and colloquially it's known as the eXecute
 bit in the context of, e.g., W^X protection.)
 
 So the kernel will consider them both to be `text segment', and
 neither to be `data segment', and eventually conclude that the
 executable's `data size' is zero:
 
     703 	epp->ep_taddr = epp->ep_tsize = ELFDEFNNAME(NO_ADDR);
     704 	epp->ep_daddr = epp->ep_dsize = ELFDEFNNAME(NO_ADDR);
 ...
     776 			/*
     777 			 * Consider this as text segment, if it is executable.
     778 			 * If there is more than one text segment, pick the
     779 			 * largest.
     780 			 */
     781 			if (ph[i].p_flags & PF_X) {
     782 				if (epp->ep_taddr == ELFDEFNNAME(NO_ADDR) ||
     783 				    size > epp->ep_tsize) {
     784 					epp->ep_taddr = addr;
     785 					epp->ep_tsize = size;
     786 				}
     787 				end_text = addr + size;
     788 			} else {
     789 				epp->ep_daddr = addr;
     790 				epp->ep_dsize = size;
     791 			}
 ...
     828 	if (epp->ep_daddr == ELFDEFNNAME(NO_ADDR)) {
     829 		epp->ep_daddr = round_page(end_text);
     830 		epp->ep_dsize = 0;
     831 	}
 
 https://nxr.NetBSD.org/xref/src/sys/kern/exec_elf.c?r=1.107#776
 
 Is it expected that sparc executables have only RX and RWX segments,
 no separate R or RW segments?  Does sparc have some stupid ABI design
 that is incompatible with W^X?