libc: Always use our own copy of sys_errlist and sys_nerr (.so only).

This ensures strerror() and friends continue to work correctly even if a
(non-PIE) executable linked against an older libc imports sys_errlist (which
causes sys_errlist to refer to the executable's copy with a size fixed when
that executable was linked).

The executable's use of sys_errlist remains broken because it uses the
current value of sys_nerr and may access past the bounds of the array.

Different from the message "Using sys_errlist from executables is not
ABI-stable" on freebsd-arch, this change does not affect the static library.
There seems no reason to prevent overriding the error messages in the static
library.

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/libc/gen/errlst.c b/lib/libc/gen/errlst.c
index 7b4fd62..f8fe968 100644
--- a/lib/libc/gen/errlst.c
+++ b/lib/libc/gen/errlst.c
@@ -34,6 +34,7 @@ static char sccsid[] = "@(#)errlst.c	8.2 (Berkeley) 11/16/93";
 __FBSDID("$FreeBSD$");
 
 #include <stdio.h>
+#include "errlst.h"
 
 const char *const sys_errlist[] = {
 	"No error: 0",				/*  0 - ENOERROR */
@@ -156,3 +157,8 @@ const char *const sys_errlist[] = {
 	"Previous owner died",			/* 96 - EOWNERDEAD */
 };
 const int sys_nerr = sizeof(sys_errlist) / sizeof(sys_errlist[0]);
+
+#ifdef PIC
+__strong_reference(sys_errlist, __hidden_sys_errlist);
+__strong_reference(sys_nerr, __hidden_sys_nerr);
+#endif