Red Bear OS — microkernel OS in Rust, based on Redox

Derivative of Redox OS (https://www.redox-os.org) adding:
- AMD GPU driver (amdgpu) via LinuxKPI compat layer
- ext4 filesystem support (ext4d scheme daemon)
- ACPI fixes for AMD bare metal (x2APIC, DMAR, IVRS, MCFG)
- Custom branding (hostname, os-release, boot identity)

Build system is full upstream Redox with RBOS overlay in local/.
Patches for kernel, base, and relibc are symlinked from local/patches/
and protected from make clean/distclean. Custom recipes live in
local/recipes/ with symlinks into the recipes/ search path.

Build:  make all CONFIG_NAME=redbear-full
Sync:   ./local/scripts/sync-upstream.sh

recipes/dev/patch/01_no_rlimit.patch

@@ -0,0 +1,35 @@
+diff -ru source/lib/getdtablesize.c source-new/lib/getdtablesize.c
+--- source/lib/getdtablesize.c	2015-03-06 16:31:45.000000000 -0800
++++ source-new/lib/getdtablesize.c	2017-08-08 19:33:33.993874985 -0700
+@@ -106,15 +106,6 @@
+ int
+ getdtablesize (void)
+ {
+-  struct rlimit lim;
+-
+-  if (getrlimit (RLIMIT_NOFILE, &lim) == 0
+-      && 0 <= lim.rlim_cur && lim.rlim_cur <= INT_MAX
+-      && lim.rlim_cur != RLIM_INFINITY
+-      && lim.rlim_cur != RLIM_SAVED_CUR
+-      && lim.rlim_cur != RLIM_SAVED_MAX)
+-    return lim.rlim_cur;
+-
+   return INT_MAX;
+ }
+ 
+Only in source-new/lib: getdtablesize.c.orig
+diff -ru source/src/safe.c source-new/src/safe.c
+--- source/src/safe.c	2015-03-06 16:34:20.000000000 -0800
++++ source-new/src/safe.c	2017-08-08 19:33:53.447430811 -0700
+@@ -92,11 +92,7 @@
+ 
+ static void init_dirfd_cache (void)
+ {
+-  struct rlimit nofile;
+-
+   max_cached_fds = 8;
+-  if (getrlimit (RLIMIT_NOFILE, &nofile) == 0)
+-    max_cached_fds = MAX (nofile.rlim_cur / 4, max_cached_fds);
+ 
+   cached_dirfds = hash_initialize (max_cached_fds,
+ 				   NULL,

recipes/dev/patch/02_no_chown.patch

@@ -0,0 +1,19 @@
+diff -ru source/src/util.c source-new/src/util.c
+--- source/src/util.c	2015-03-06 16:34:20.000000000 -0800
++++ source-new/src/util.c	2017-08-11 18:24:56.991729200 -0700
+@@ -271,6 +271,7 @@
+ 
+       /* May fail if we are not privileged to set the file owner, or we are
+          not in group instat.st_gid.  Ignore those errors.  */
++      /*
+       if ((uid != -1 || gid != -1)
+ 	  && safe_lchown (to, uid, gid) != 0
+ 	  && (errno != EPERM
+@@ -281,6 +282,7 @@
+ 		(uid == -1) ? "owner" : "owning group",
+ 		S_ISLNK (mode) ? "symbolic link" : "file",
+ 		quotearg (to));
++      */
+     }
+   if (attr & FA_XATTRS)
+     if (copy_attr (from, to) != 0

recipes/dev/patch/03_renameat2.patch

@@ -0,0 +1,15 @@
+--- source-old/lib/renameat2.c	2018-02-03 05:41:53.000000000 -0700
++++ source/lib/renameat2.c	2025-11-01 08:39:54.945513820 -0600
+@@ -70,6 +70,7 @@
+    Obey FLAGS when doing the renaming.  If FLAGS is zero, this
+    function is equivalent to renameat (FD1, SRC, FD2, DST).  */
+ 
++#if !defined(__redox__)
+ int
+ renameat2 (int fd1, char const *src, int fd2, char const *dst,
+            unsigned int flags)
+@@ -225,3 +226,4 @@
+ 
+ #endif /* !HAVE_RENAMEAT */
+ }
++#endif

recipes/dev/patch/recipe.toml

@@ -0,0 +1,28 @@
+[source]
+tar = "https://ftp.gnu.org/gnu/patch/patch-2.7.6.tar.xz"
+blake3 = "d46d14c12aa4ea51e356bf92091c368fd871e1d770b94bc29027886737aecd5f"
+patches = [
+    "01_no_rlimit.patch",
+    "02_no_chown.patch",
+    "03_renameat2.patch",
+]
+script = """
+wget -O build-aux/config.sub "https://gitlab.redox-os.org/redox-os/gnu-config/-/raw/master/config.sub?inline=false"
+autoreconf
+"""
+
+[build]
+template = "custom"
+script = """
+COOKBOOK_CONFIGURE="${COOKBOOK_SOURCE}/configure"
+COOKBOOK_CONFIGURE_FLAGS=(
+    --host="${TARGET}"
+    --prefix="/"
+    --build="$(gcc -dumpmachine)"
+)
+
+cookbook_configure
+
+${TARGET}-strip "${COOKBOOK_STAGE}/bin/"*
+rm -rf "${COOKBOOK_STAGE}/share" "${COOKBOOK_STAGE}/lib"
+"""