mrust-libs: solve(?) the perpetual "guard page" problem that kept showing up when building mrust-rustc & mrust-cargo (try relying on NetBSD native guard area management instead of mprotect)

[Dave Berger <pkgsrc-mrust%web5by5.com@localhost>]

Module Name:	pkgsrc-wip
Committed By:	Dave Berger <pkgsrc-mrust%web5by5.com@localhost>
Pushed By:	dave
Date:		Sat Jan 22 16:29:10 2022 -0500
Changeset:	92fd16dbba5dd3cb6c440a4de0af9e950af20926

Modified Files:
	mrust-libs/distinfo
	mrust-libs/patches/patch-.._rustc-1.39.0-src_src_libstd_sys_unix_thread.rs

Log Message:
mrust-libs: solve(?) the perpetual "guard page" problem
that kept showing up when building mrust-rustc & mrust-cargo
(try relying on NetBSD native guard area management instead of mprotect)

To see a diff of this commit:
https://wip.pkgsrc.org/cgi-bin/gitweb.cgi?p=pkgsrc-wip.git;a=commitdiff;h=92fd16dbba5dd3cb6c440a4de0af9e950af20926

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.

diffstat:
 mrust-libs/distinfo                                |  2 +-
 ..._rustc-1.39.0-src_src_libstd_sys_unix_thread.rs | 47 ++++++++++++++--------
 2 files changed, 31 insertions(+), 18 deletions(-)

diffs:
diff --git a/mrust-libs/distinfo b/mrust-libs/distinfo
index b45a5e3ede..d89e49815d 100644
--- a/mrust-libs/distinfo
+++ b/mrust-libs/distinfo
@@ -8,7 +8,7 @@ SHA1 (mrustc/rustc-1.39.0-src.tar.gz) = 82ef6f3b88b8d5e3bfa2fab67bbacf5d6f6ba6bb
 RMD160 (mrustc/rustc-1.39.0-src.tar.gz) = d5b04b87fc336e3be7d592f70de0363aa66622aa
 SHA512 (mrustc/rustc-1.39.0-src.tar.gz) = 77be74410b9f7a2e9f78f7a9860964e122ab9518553acc2cc80d5abeecf3302e9b3ed1fd29e022cccff1f9ff4a568b4015c0d3ac0a524f06e38e9cb360a3341e
 Size (mrustc/rustc-1.39.0-src.tar.gz) = 152803201 bytes
-SHA1 (patch-.._rustc-1.39.0-src_src_libstd_sys_unix_thread.rs) = 37e12f1cc16a21d940b4cbe5ccfa0baec69d366e
+SHA1 (patch-.._rustc-1.39.0-src_src_libstd_sys_unix_thread.rs) = b787f0118df7f01a37b4f6205c4e56614ca74876
 SHA1 (patch-Makefile) = 3326e1e1f9dbe83f7b3147ee073c3c821d4ce939
 SHA1 (patch-minicargo.mk) = a13fa4b05e443871b8d25aa7f008069f5dd2f91d
 SHA1 (patch-script-overrides_stable-1.39.0-linux_build__std.txt) = 728fce6fbbd81db342bdc1eb0f6ac57abf45f8b7
diff --git a/mrust-libs/patches/patch-.._rustc-1.39.0-src_src_libstd_sys_unix_thread.rs b/mrust-libs/patches/patch-.._rustc-1.39.0-src_src_libstd_sys_unix_thread.rs
index 0ee7061987..0177a2c313 100644
--- a/mrust-libs/patches/patch-.._rustc-1.39.0-src_src_libstd_sys_unix_thread.rs
+++ b/mrust-libs/patches/patch-.._rustc-1.39.0-src_src_libstd_sys_unix_thread.rs
@@ -2,23 +2,36 @@ $NetBSD$
 
 --- ../rustc-1.39.0-src/src/libstd/sys/unix/thread.rs.orig	2019-11-04 15:45:21.000000000 +0000
 +++ ../rustc-1.39.0-src/src/libstd/sys/unix/thread.rs
-@@ -330,14 +330,19 @@ pub mod guard {
-             // than the initial mmap() used, so we mmap() here with
-             // read/write permissions and only then mprotect() it to
-             // no permissions at all. See issue #50313.
--            let result = mmap(stackaddr, PAGE_SIZE, PROT_READ | PROT_WRITE,
--                              MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0);
--            if result != stackaddr || result == MAP_FAILED {
--                panic!("failed to allocate a guard page");
--            }
-+//          let result = mmap(stackaddr, PAGE_SIZE, PROT_READ | PROT_WRITE,
-+//                            MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0);
-+//          if result != stackaddr || result == MAP_FAILED {
-+//              println!( "stackaddr = {}", stackaddr as u64 );
-+//              println!( "mmap() -> result {}", result as u64 );
-+//              println!( "mmap() -> ERRNO {}", os::errno() as u64 );
-+//              panic!("failed to allocate a guard page");
-+//          }
+@@ -321,6 +321,20 @@ pub mod guard {
+             // trust that the kernel's own stack guard will work.
+             let stackaddr = stackaddr as usize;
+             Some(stackaddr - PAGE_SIZE..stackaddr)
++        } else if cfg!(target_os = "netbsd") {
++            // [The following should be reviewed/confirmed, -DLB]:
++            // Using the default else clause below, sporadic guard page
++            // errors were occurring during builds of rustc & cargo with
++            // mrustc on NetBSD; however, NetBSD has a kernel-based
++            // guard area mechanism too.  Therefore, try relying on that
++            // instead of the default mmap/mprotect solution; but note:
++            // if userland code changes the stack address, the NetBSD
++            // kernel-based guard mechanism is deactivated (see
++            // pthread_attr_getstack(3)) and the userland code must
++            // manage a guard area itself.  Fortunately, the stack
++            // appears to be unchanged by this version of thread.rs
++            let stackaddr = stackaddr as usize;
++            Some(stackaddr - PAGE_SIZE..stackaddr)
+         } else {
+             // Reallocate the last page of the stack.
+             // This ensures SIGBUS will be raised on
+@@ -333,11 +347,16 @@ pub mod guard {
+             let result = mmap(stackaddr, PAGE_SIZE, PROT_READ | PROT_WRITE,
+                               MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0);
+             if result != stackaddr || result == MAP_FAILED {
++                println!( "stackaddr = {}", stackaddr as u64 );
++                println!( "mmap() -> result {}", result as u64 );
++                println!( "mmap() -> ERRNO {}", os::errno() as u64 );
+                 panic!("failed to allocate a guard page");
+             }
  
              let result = mprotect(stackaddr, PAGE_SIZE, PROT_NONE);
              if result != 0 {