The branch main has been updated by kib:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=e2879ece4314eed2d22fe484bd4adfcbb1009685

commit e2879ece4314eed2d22fe484bd4adfcbb1009685
Author:     Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2022-09-12 19:45:21 +0000
Commit:     Konstantin Belousov <k...@freebsd.org>
CommitDate: 2022-09-16 20:24:06 +0000

    libc, libthr: use AT_USRSTACK{BASE,LIM} instead of sysctl("kern.usrstack") 
and get_rlimit(RLIMIT_STACK)
    
    Reviewed by:    brooks, imp (previous version)
    Discussed with: markj
    Sponsored by:   The FreeBSD Foundation
    MFC after:      2 weeks
    Differential revision:  https://reviews.freebsd.org/D36540
---
 lib/libc/gen/elf_utils.c      | 27 ++++++++++++++++-----------
 lib/libthr/thread/thr_init.c  | 25 +++++++++++++++++--------
 lib/libthr/thread/thr_stack.c | 26 ++++++++++++++++----------
 3 files changed, 49 insertions(+), 29 deletions(-)

diff --git a/lib/libc/gen/elf_utils.c b/lib/libc/gen/elf_utils.c
index ea5cc25f8601..ed3ac843f7c3 100644
--- a/lib/libc/gen/elf_utils.c
+++ b/lib/libc/gen/elf_utils.c
@@ -29,6 +29,7 @@
  */
 
 #include <sys/param.h>
+#include <sys/auxv.h>
 #include <sys/mman.h>
 #include <sys/resource.h>
 #include <sys/sysctl.h>
@@ -77,19 +78,23 @@ __libc_map_stacks_exec(void)
 {
        int mib[2];
        struct rlimit rlim;
-       u_long usrstack;
+       u_long usrstack, stacksz;
        size_t len;
        
-       mib[0] = CTL_KERN;
-       mib[1] = KERN_USRSTACK;
-       len = sizeof(usrstack);
-       if (sysctl(mib, nitems(mib), &usrstack, &len, NULL, 0)
-           == -1)
-               return;
-       if (getrlimit(RLIMIT_STACK, &rlim) == -1)
-               return;
-       mprotect((void *)(uintptr_t)(usrstack - rlim.rlim_cur),
-           rlim.rlim_cur, _rtld_get_stack_prot());
+       if (_elf_aux_info(AT_USRSTACKBASE, &usrstack, sizeof(usrstack)) != 0) {
+               mib[0] = CTL_KERN;
+               mib[1] = KERN_USRSTACK;
+               len = sizeof(usrstack);
+               if (sysctl(mib, nitems(mib), &usrstack, &len, NULL, 0) == -1)
+                       return;
+       }
+       if (_elf_aux_info(AT_USRSTACKLIM, &stacksz, sizeof(stacksz)) != 0) {
+               if (getrlimit(RLIMIT_STACK, &rlim) == -1)
+                       return;
+               stacksz = rlim.rlim_cur;
+       }
+       mprotect((void *)(uintptr_t)(usrstack - stacksz), stacksz,
+           _rtld_get_stack_prot());
 }
 
 #pragma weak __pthread_map_stacks_exec
diff --git a/lib/libthr/thread/thr_init.c b/lib/libthr/thread/thr_init.c
index 0ab051e57994..b9d3265a05dc 100644
--- a/lib/libthr/thread/thr_init.c
+++ b/lib/libthr/thread/thr_init.c
@@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
 
 #include "namespace.h"
 #include <sys/param.h>
+#include <sys/auxv.h>
 #include <sys/signalvar.h>
 #include <sys/ioctl.h>
 #include <sys/link_elf.h>
@@ -462,18 +463,26 @@ init_private(void)
        if (init_once == 0) {
                __thr_pshared_init();
                __thr_malloc_init();
+
                /* Find the stack top */
-               mib[0] = CTL_KERN;
-               mib[1] = KERN_USRSTACK;
-               len = sizeof (_usrstack);
-               if (sysctl(mib, nitems(mib), &_usrstack, &len, NULL, 0) == -1)
-                       PANIC("Cannot get kern.usrstack from sysctl");
+               if (elf_aux_info(AT_USRSTACKBASE, &_usrstack,
+                   sizeof(_usrstack)) != 0) {
+                       mib[0] = CTL_KERN;
+                       mib[1] = KERN_USRSTACK;
+                       len = sizeof (_usrstack);
+                       if (sysctl(mib, nitems(mib), &_usrstack, &len,
+                           NULL, 0) == -1)
+                               PANIC("Cannot get kern.usrstack from sysctl");
+               }
                env_bigstack = getenv("LIBPTHREAD_BIGSTACK_MAIN");
                env_splitstack = getenv("LIBPTHREAD_SPLITSTACK_MAIN");
                if (env_bigstack != NULL || env_splitstack == NULL) {
-                       if (getrlimit(RLIMIT_STACK, &rlim) == -1)
-                               PANIC("Cannot get stack rlimit");
-                       _thr_stack_initial = rlim.rlim_cur;
+                       if (elf_aux_info(AT_USRSTACKLIM, &_thr_stack_initial,
+                           sizeof(_thr_stack_initial)) != 0) {
+                               if (getrlimit(RLIMIT_STACK, &rlim) == -1)
+                                       PANIC("Cannot get stack rlimit");
+                               _thr_stack_initial = rlim.rlim_cur;
+                       }
                }
                _thr_is_smp = sysconf(_SC_NPROCESSORS_CONF);
                if (_thr_is_smp == -1)
diff --git a/lib/libthr/thread/thr_stack.c b/lib/libthr/thread/thr_stack.c
index af396fe2ba93..34536ecfad2e 100644
--- a/lib/libthr/thread/thr_stack.c
+++ b/lib/libthr/thread/thr_stack.c
@@ -31,6 +31,7 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/auxv.h>
 #include <sys/mman.h>
 #include <sys/queue.h>
 #include <sys/resource.h>
@@ -149,18 +150,23 @@ singlethread_map_stacks_exec(void)
 {
        int mib[2];
        struct rlimit rlim;
-       u_long usrstack;
+       u_long usrstack, stacksz;
        size_t len;
 
-       mib[0] = CTL_KERN;
-       mib[1] = KERN_USRSTACK;
-       len = sizeof(usrstack);
-       if (sysctl(mib, nitems(mib), &usrstack, &len, NULL, 0) == -1)
-               return;
-       if (getrlimit(RLIMIT_STACK, &rlim) == -1)
-               return;
-       mprotect((void *)(uintptr_t)(usrstack - rlim.rlim_cur),
-           rlim.rlim_cur, _rtld_get_stack_prot());
+       if (elf_aux_info(AT_USRSTACKBASE, &usrstack, sizeof(usrstack)) != 0) {
+               mib[0] = CTL_KERN;
+               mib[1] = KERN_USRSTACK;
+               len = sizeof(usrstack);
+               if (sysctl(mib, nitems(mib), &usrstack, &len, NULL, 0) == -1)
+                       return;
+       }
+       if (elf_aux_info(AT_USRSTACKLIM, &stacksz, sizeof(stacksz)) != 0) {
+               if (getrlimit(RLIMIT_STACK, &rlim) == -1)
+                       return;
+               stacksz = rlim.rlim_cur;
+       }
+       mprotect((void *)(uintptr_t)(usrstack - stacksz), stacksz,
+           _rtld_get_stack_prot());
 }
 
 void

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