git: 74408970498a - stable/13 - Clarify code comments on ASLR default settings

The branch stable/13 has been updated by emaste:

URL: https://cgit.FreeBSD.org/src/commit/?id=74408970498a7934672a73f8d0894401ba54b813

commit 74408970498a7934672a73f8d0894401ba54b813
Author:     Ed Maste <emaste@FreeBSD.org>
AuthorDate: 2022-08-05 14:01:07 +0000
Commit:     Ed Maste <emaste@FreeBSD.org>
CommitDate: 2022-09-04 23:57:28 +0000

    Clarify code comments on ASLR default settings
    
    Sponsored by:   The FreeBSD Foundation
    
    (cherry picked from commit f0687f3e0e4d09edce906308f79b312abd574553)
---
 sys/kern/imgact_elf.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c
index 548a65a6f677..34cfef0d7cd9 100644
--- a/sys/kern/imgact_elf.c
+++ b/sys/kern/imgact_elf.c
@@ -173,10 +173,9 @@ SYSCTL_NODE(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, aslr,
 #define	ASLR_NODE_OID	__CONCAT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), _aslr)
 
 /*
- * While for 64-bit machines ASLR works properly, there are
- * still some problems when using 32-bit architectures. For this
- * reason ASLR is only enabled by default when running native
- * 64-bit non-PIE executables.
+ * Enable ASLR by default for 64-bit non-PIE binaries.  32-bit architectures
+ * have limited address space (which can cause issues for applications with
+ * high memory use) so we leave it off there.
  */
 static int __elfN(aslr_enabled) = __ELF_WORD_SIZE == 64;
 SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, enable, CTLFLAG_RWTUN,
@@ -185,7 +184,7 @@ SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, enable, CTLFLAG_RWTUN,
     ": enable address map randomization");
 
 /*
- * Enable ASLR only for 64-bit PIE binaries by default.
+ * Enable ASLR by default for 64-bit PIE binaries.
  */
 static int __elfN(pie_aslr_enabled) = __ELF_WORD_SIZE == 64;
 SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, pie_enable, CTLFLAG_RWTUN,
@@ -194,9 +193,9 @@ SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, pie_enable, CTLFLAG_RWTUN,
     ": enable address map randomization for PIE binaries");
 
 /*
- * Sbrk is now deprecated and it can be assumed, that in most
- * cases it will not be used anyway. This setting is valid only
- * for the ASLR enabled and allows for utilizing the bss grow region.
+ * Sbrk is deprecated and it can be assumed that in most cases it will not be
+ * used anyway. This setting is valid only with ASLR enabled, and allows ASLR
+ * to use the bss grow region.
  */
 static int __elfN(aslr_honor_sbrk) = 0;
 SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, honor_sbrk, CTLFLAG_RW,