jserv · jserv · May 1, 2026 · May 1, 2026
diff --git a/build.sh b/build.sh
@@ -23,7 +23,14 @@ LINUX_VERSION=7.0
 
 BINUTILS_URL=https://ftp.gnu.org/gnu/binutils/binutils-${BINUTILS_VERSION}.tar.xz
 GCC_URL=https://ftp.gnu.org/gnu/gcc/gcc-${GCC_VERSION}/gcc-${GCC_VERSION}.tar.xz
-UCLIBC_NG_URL=https://downloads.uclibc-ng.org/releases/${UCLIBC_NG_VERSION}/uClibc-ng-${UCLIBC_NG_VERSION}.tar.xz
+# GitHub auto-archive. The canonical mirror at downloads.uclibc-ng.org
+# has been observed returning HTTP 522 (Cloudflare-to-origin failure)
+# for extended windows; GitHub's tag-based source archive is permanent
+# and byte-equivalent to the upstream tarball content (same 5,527-file
+# tree, only the top-level directory uses lowercase 'u' which we rename
+# back below to keep configs/uClibc-ng-*.config and the rest of this
+# script unchanged).
+UCLIBC_NG_URL=https://github.com/wbx-github/uclibc-ng/archive/refs/tags/v${UCLIBC_NG_VERSION}.tar.gz
 BUSYBOX_URL=https://busybox.net/downloads/busybox-${BUSYBOX_VERSION}.tar.bz2
 LINUX_URL=https://www.kernel.org/pub/linux/kernel/v7.x/linux-${LINUX_VERSION}.tar.xz
 
@@ -63,7 +70,7 @@ mkdir -p "${LOGDIR}" "${STATE_DIR}"
 # To populate missing checksums: sha256sum downloads/*
 CHECKSUM_binutils="binutils-${BINUTILS_VERSION}.tar.xz=d75a94f4d73e7a4086f7513e67e439e8fcdcbb726ffe63f4661744e6256b2cf2"
 CHECKSUM_gcc="gcc-${GCC_VERSION}.tar.xz=438fd996826b0c82485a29da03a72d71d6e3541a83ec702df4271f6fe025d24e"
-CHECKSUM_uclibc="uClibc-ng-${UCLIBC_NG_VERSION}.tar.xz=8bc734b584e23ff6ae3d0ebb4c0fb1d1d814c58c82822b93130d436afa7ace8b"
+CHECKSUM_uclibc="v${UCLIBC_NG_VERSION}.tar.gz=f49704e0affc75fde9ee4e870c20e53c1d807eca2a4683377b359b8361e84312"
 CHECKSUM_busybox="busybox-${BUSYBOX_VERSION}.tar.bz2=3311dff32e746499f4df0d5df04d7eb396382d7e108bb9250e7b519b837043a4"
 CHECKSUM_linux="linux-${LINUX_VERSION}.tar.xz=bb7f6d80b387c757b7d14bb93028fcb90f793c5c0d367736ee815a100b3891f0"
 
@@ -410,7 +417,12 @@ build_uClibc() {
     echo "BUILD: building uClibc-${UCLIBC_NG_VERSION}"
     fetch_file "${UCLIBC_NG_URL}" "${CHECKSUM_uclibc}"
 
-    extract_source "uClibc-ng-${UCLIBC_NG_VERSION}.tar.xz" "uClibc-ng-${UCLIBC_NG_VERSION}" -xJf
+    extract_source "v${UCLIBC_NG_VERSION}.tar.gz" "uClibc-ng-${UCLIBC_NG_VERSION}" -xzf
+    # GitHub source archive unpacks to lowercase 'uclibc-ng-X.Y.Z'; rename
+    # to the canonical-tarball capitalization so configs/ and stage_clean
+    # references stay valid. extract_source's own "reuse" check above
+    # already short-circuits on subsequent runs once the rename has taken.
+    [ -d "uClibc-ng-${UCLIBC_NG_VERSION}" ] || mv "uclibc-ng-${UCLIBC_NG_VERSION}" "uClibc-ng-${UCLIBC_NG_VERSION}"
     cp configs/uClibc-ng-${UCLIBC_NG_VERSION}-${FLAVOR}.config uClibc-ng-${UCLIBC_NG_VERSION}/.config
     cd uClibc-ng-${UCLIBC_NG_VERSION}
 
@@ -654,7 +666,7 @@ build_linux() {
     cd linux-${LINUX_VERSION}
 
     # Apply linux-tiny patches for reduced memory footprint and LTO support
-    for p in ../patches/0002-*.patch ../patches/0003-*.patch ../patches/0004-*.patch ../patches/0005-*.patch ../patches/0006-*.patch ../patches/0010-*.patch ../patches/0011-*.patch; do
+    for p in ../patches/0002-*.patch ../patches/0003-*.patch ../patches/0004-*.patch ../patches/0005-*.patch ../patches/0006-*.patch ../patches/0010-*.patch ../patches/0011-*.patch ../patches/0012-*.patch ../patches/0013-*.patch; do
         [ -f "${p}" ] || continue
         apply_patch_once "${p}"
     done
@@ -896,6 +908,29 @@ build_linux() {
     echo "# CONFIG_STACKPROTECTOR is not set" >>.config
     echo "# CONFIG_STACKPROTECTOR_STRONG is not set" >>.config
 
+    # Scheduler trim: Linux 7.0 removed CONFIG_SCHED_DEBUG and unified
+    # debug.c into build_utility.c.  Patch 0012 reintroduces a knob
+    # (SCHED_DEBUG_OUTPUT, default y) that wraps debug.c body in #ifdef
+    # and provides empty stubs for the externally-called symbols.
+    # /proc/<pid>/sched returns empty seq_file; OOPS sched_show_task
+    # path is unaffected (defined in core.c).  Measured: -4,278 bytes /
+    # 16 symbols on the production vmlinux .text.
+    echo "# CONFIG_SCHED_DEBUG_OUTPUT is not set" >>.config
+
+    # Patch 0013 mirrors 0012 for deadline.c: SCHED_DEADLINE_CLASS
+    # default y; set n to wrap deadline.c body in #ifdef and substitute
+    # a stub class (DEFINE_SCHED_CLASS(dl) with pick_task=NULL_returner,
+    # all other callbacks NULL).  __checkparam_dl returns false so
+    # sched_setattr with policy=6 is rejected with -EPERM and no task
+    # ever joins SCHED_DEADLINE.  Any later attempt to program a DL
+    # server is rejected with -EOPNOTSUPP, so the scheduler must also
+    # keep the cgroup-bandwidth/group-sched knobs below disabled.
+    # Measured: -10,530 bytes / 81 symbols.
+    echo "# CONFIG_SCHED_DEADLINE_CLASS is not set" >>.config
+    echo "# CONFIG_PSI is not set" >>.config
+    echo "# CONFIG_CGROUPS is not set" >>.config
+    echo "# CONFIG_SCHED_AUTOGROUP is not set" >>.config
+
     run_logged "olddefconfig" kernel_make olddefconfig
 
     # Verify critical config options survived olddefconfig resolution.
@@ -953,7 +988,12 @@ build_linux() {
         "# CONFIG_DEBUG_BUGVERBOSE is not set" \
         "# CONFIG_RD_ZSTD is not set" \
         "# CONFIG_RD_LZ4 is not set" \
-        "# CONFIG_RD_XZ is not set"; do
+        "# CONFIG_RD_XZ is not set" \
+        "# CONFIG_SCHED_DEBUG_OUTPUT is not set" \
+        "# CONFIG_SCHED_DEADLINE_CLASS is not set" \
+        "# CONFIG_PSI is not set" \
+        "# CONFIG_CGROUPS is not set" \
+        "# CONFIG_SCHED_AUTOGROUP is not set"; do
         if ! grep -q "^${opt}\$" .config; then
             echo "ERROR: expected '${opt}' in .config after olddefconfig"
             exit 1
@@ -1003,9 +1043,13 @@ build_linux() {
     #   STACKPROTECTOR_STRONG     -- depends on STACKPROTECTOR=y
     #   LOGO/A11Y_BRAILLE_CONSOLE -- depend on the VT stack
     #   DEVTMPFS_MOUNT            -- depends on DEVTMPFS=y
+    #   CGROUP_SCHED/*_GROUP_SCHED/CFS_BANDWIDTH -- depend on CGROUPS=y
     for sym in SHMEM AUDIT POSIX_MQUEUE SECURITY TASKSTATS PCI \
                STACKPROTECTOR_STRONG LOGO A11Y_BRAILLE_CONSOLE \
-               DEVTMPFS_MOUNT; do
+               DEVTMPFS_MOUNT \
+               CGROUP_SCHED FAIR_GROUP_SCHED CFS_BANDWIDTH RT_GROUP_SCHED \
+               SCHED_CORE NUMA_BALANCING UCLAMP_TASK \
+               SCHED_THERMAL_PRESSURE SCHEDSTATS; do
         if grep -q "^CONFIG_${sym}=y\$" .config; then
             echo "ERROR: CONFIG_${sym}=y survived olddefconfig (subsystem disable broken?)"
             exit 1

diff --git a/patches/0012-tiny-sched-no-debug-output.patch b/patches/0012-tiny-sched-no-debug-output.patch
@@ -0,0 +1,101 @@
+From: Jim Huang <jserv@ccns.ncku.edu.tw>
+Subject: [PATCH] tiny: sched: gate debug.c behind CONFIG_SCHED_DEBUG_OUTPUT
+
+Linux 7.0 removed the historical CONFIG_SCHED_DEBUG gate; debug.c is now
+unconditionally included via build_utility.c.  On a NOMMU image with no
+userspace reader of /proc/<pid>/sched, no debugfs sched-domain consumer,
+and no sysrq input device, the file is ~4KB of dead .text and .rodata.
+
+Re-introduce a knob without resurrecting the old name (which other code
+still references in deprecation comments).  CONFIG_SCHED_DEBUG_OUTPUT
+defaults to y so mainline behavior is preserved; setting it to n wraps
+the body of debug.c in #ifdef and provides empty stubs for the
+externally-called symbols that lack existing header stubs:
+
+  sched_debug_verbose             -- topology.c reads this flag
+  sysrq_sched_debug_show          -- core.c show_state_filter
+  resched_latency_warn            -- core.c sched_tick latency check
+  print_cfs_rq / print_rt_rq      -- print_*_stats bodies in fair.c, rt.c
+  print_dl_rq                     -- print_dl_stats body in deadline.c
+  print_numa_stats                -- print_cfs_stats body in fair.c
+                                     (only when CONFIG_NUMA_BALANCING)
+  proc_sched_show_task            -- fs/proc/base.c /proc/<pid>/sched read
+  proc_sched_set_task             -- fs/proc/base.c /proc/<pid>/sched write
+  update_sched_domain_debugfs     -- topology.c sched-domain rebuild path
+  dirty_sched_domain_sysctl       -- topology.c sched-domain sysctl path
+
+OOPS/panic backtraces are unaffected because sched_show_task and
+dump_cpu_task live in core.c, not debug.c.  /proc/<pid>/sched returns an
+empty seq_file when read.  Boot-path callers silently no-op.
+
+Measured on Cortex-M4 nommu mps2-an386 (linux-7.0): SCHED_DEBUG_OUTPUT=n
+drops 4,278 bytes / 16 symbols from .text per nm --size-sort against the
+production vmlinux.
+
+---
+ init/Kconfig         | 14 ++++++++++++++
+ kernel/sched/debug.c | 22 ++++++++++++++++++++++
+ 2 files changed, 36 insertions(+)
+
+diff --git a/init/Kconfig b/init/Kconfig
+--- a/init/Kconfig
++++ b/init/Kconfig
+@@ -932,6 +932,20 @@ config SCHED_PROXY_EXEC
+ 	  This option enables proxy execution, a mechanism for mutex-owning
+ 	  tasks to inherit the scheduling context of higher priority waiters.
+
++config SCHED_DEBUG_OUTPUT
++	bool "Scheduler debug/output paths"
++	default y
++	help
++	  Build kernel/sched/debug.c, which provides /proc/<pid>/sched,
++	  /sys/kernel/debug/sched/* (when DEBUG_FS=y), the sysrq scheduler
++	  dump, and the print_cfs_rq / print_rt_rq / print_dl_rq /
++	  print_numa_stats formatters.
++
++	  Say N on size-constrained NOMMU images that never read
++	  /proc/<pid>/sched and have no debugfs sched-domain consumer.
++	  Boot-path callers become no-ops; OOPS/panic backtraces are
++	  unaffected (sched_show_task lives in core.c).
++
+ endmenu
+
+ #
+diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
+--- a/kernel/sched/debug.c
++++ b/kernel/sched/debug.c
+@@ -9,6 +9,8 @@
+ #include <linux/debugfs.h>
+ #include <linux/nmi.h>
+ #include "sched.h"
++
++#ifdef CONFIG_SCHED_DEBUG_OUTPUT
+
+ /*
+  * This allows printing both to /sys/kernel/debug/sched/debug and
+@@ -1388,3 +1390,25 @@ void resched_latency_warn(int cpu, u64 latency)
+ 	       cpu, latency, cpu_rq(cpu)->ticks_without_resched);
+ 	dump_stack();
+ }
++
++#else /* !CONFIG_SCHED_DEBUG_OUTPUT */
++
++__read_mostly bool sched_debug_verbose;
++
++void sysrq_sched_debug_show(void) { }
++void resched_latency_warn(int cpu, u64 latency) { }
++void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) { }
++void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq) { }
++void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq) { }
++#ifdef CONFIG_NUMA_BALANCING
++void print_numa_stats(struct seq_file *m, int node, unsigned long tsf,
++		      unsigned long tpf, unsigned long gsf, unsigned long gpf)
++{ }
++#endif
++void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
++			  struct seq_file *m) { }
++void proc_sched_set_task(struct task_struct *p) { }
++void update_sched_domain_debugfs(void) { }
++void dirty_sched_domain_sysctl(int cpu) { }
++
++#endif /* CONFIG_SCHED_DEBUG_OUTPUT */
diff --git a/patches/0013-tiny-sched-no-deadline-class.patch b/patches/0013-tiny-sched-no-deadline-class.patch
@@ -0,0 +1,159 @@
+From: Jim Huang <jserv@ccns.ncku.edu.tw>
+Subject: [PATCH] tiny: sched: gate deadline.c behind CONFIG_SCHED_DEADLINE_CLASS
+
+Linux 7.0 deleted the historical CONFIG_SCHED_DEADLINE gate; deadline.c
+is now unconditionally included via build_policy.c.  On a NOMMU image
+that never sets SCHED_DEADLINE policy (BusyBox CHRT applet is off, no
+init script issues sched_setattr with policy=6), the file is ~10.5KB of
+dead .text plus its DL bandwidth/server bookkeeping.
+
+Re-introduce a knob without resurrecting the old name.
+CONFIG_SCHED_DEADLINE_CLASS defaults to y so mainline behavior is
+preserved; setting it to n wraps the body of deadline.c in #ifdef and
+provides a minimal stub class plus stubs for every externally-called
+helper.  The stub class is registered via DEFINE_SCHED_CLASS(dl) so it
+lands in the __dl_sched_class linker section between stop and rt --
+core.c::sched_class_above() BUG_ON checks at sched_init pass.  Only
+.pick_task is implemented (returns NULL); all other callbacks remain
+NULL because they fire only for tasks already in the class, and
+__checkparam_dl() rejects every attribute set so no task can ever join.
+
+External-API stubs match include/linux/sched/deadline.h and
+kernel/sched/sched.h declarations:
+
+  Class chain:
+    dl_sched_class                  -- empty class with pick_task=NULL
+  Init paths (called from core.c, fair.c, topology.c):
+    init_dl_bw / init_dl_rq / init_dl_entity
+    init_sched_dl_class / sched_init_dl_servers
+  Sysctl/global validation (called from rt.c sysctl handler):
+    sched_dl_global_validate / sched_dl_do_global
+  Syscall path (sched_setattr / sched_getattr):
+    sched_dl_overflow      -- returns -EPERM, blocks DL admission
+    __checkparam_dl        -- returns false, blocks DL attribute sets
+    __setparam_dl / __getparam_dl / dl_param_changed
+  CPU hotplug / cpuset:
+    dl_cpuset_cpumask_can_shrink   -- cpuset shrink validation
+  DL server (used by fair.c to back SCHED_OTHER bandwidth):
+    dl_server_init / _start / _stop / _update / _update_idle
+    __dl_server_attach_root / dl_server_apply_params
+  Bandwidth scaling helper:
+    dl_scaled_delta_exec   -- returns delta_exec unchanged
+  Globals visible to topology.c / cgroup code:
+    dl_cookie / dl_bw_visited
+  Bandwidth-management helpers used by core.c / cpuset:
+    dl_bw_deactivate / dl_bw_alloc / dl_bw_free
+
+The DL-server feature backs CFS bandwidth via a deadline entity per
+runqueue.  When the class is disabled, any attempt to program a DL
+server fails with -EOPNOTSUPP instead of pretending to succeed; the
+build disables the scheduler cgroup bandwidth knobs accordingly.
+
+Measured on Cortex-M4 nommu mps2-an386 (linux-7.0): SCHED_DEADLINE_CLASS=n
+drops 10,530 bytes / 81 symbols from .text per nm --size-sort.
+
+---
+ init/Kconfig            | 13 +++++++++
+ kernel/sched/deadline.c | 60 ++++++++++++++++++++++++++++++++++++
+ 2 files changed, 73 insertions(+)
+
+diff --git a/init/Kconfig b/init/Kconfig
+--- a/init/Kconfig
++++ b/init/Kconfig
+@@ -933,6 +933,19 @@ config SCHED_PROXY_EXEC
+ 	  This option enables proxy execution, a mechanism for mutex-owning
+ 	  tasks to inherit the scheduling context of higher priority waiters.
+
++config SCHED_DEADLINE_CLASS
++	bool "SCHED_DEADLINE earliest-deadline-first scheduling class"
++	default y
++	help
++	  Build kernel/sched/deadline.c, which implements the SCHED_DEADLINE
++	  policy (EDF + Constant Bandwidth Server) and the deadline-server
++	  bandwidth backing for SCHED_OTHER.
++
++	  Say N on size-constrained NOMMU images that never set SCHED_DEADLINE
++	  policy and need every byte back.  __checkparam_dl rejects all DL
++	  attribute sets; sched_setattr with policy=6 returns -EPERM.  Any
++	  later attempt to program a DL server fails with -EOPNOTSUPP.
++
+ endmenu
+
+ #
+diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
+--- a/kernel/sched/deadline.c
++++ b/kernel/sched/deadline.c
+@@ -20,6 +20,8 @@
+ #include <uapi/linux/sched/types.h>
+ #include "sched.h"
+ #include "pelt.h"
++
++#ifdef CONFIG_SCHED_DEADLINE_CLASS
+
+ /*
+  * Default limits for DL period; on the top end we guard against small util
+@@ -3841,3 +3843,64 @@ void print_dl_stats(struct seq_file *m, int cpu)
+ {
+ 	print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
+ }
++
++#else /* !CONFIG_SCHED_DEADLINE_CLASS */
++
++#include <linux/sched/deadline.h>
++
++/*
++ * Stub deadline scheduling class.  No task ever joins SCHED_DEADLINE
++ * because __checkparam_dl rejects every attribute set, so all callbacks
++ * except pick_task are unreachable and remain NULL.  pick_task is the
++ * one method the chain walk in pick_next_task_balance / pick_next_task
++ * invokes unconditionally per class; returning NULL forwards control to
++ * the next class (rt -> fair -> idle).
++ */
++
++static struct task_struct *pick_task_dl_stub(struct rq *rq, struct rq_flags *rf)
++{
++	return NULL;
++}
++
++DEFINE_SCHED_CLASS(dl) = {
++	.pick_task = pick_task_dl_stub,
++};
++
++u64 dl_cookie;
++
++bool dl_bw_visited(int cpu, u64 cookie) { return false; }
++int dl_bw_deactivate(int cpu) { return 0; }
++int dl_bw_alloc(int cpu, u64 dl_bw) { return 0; }
++void dl_bw_free(int cpu, u64 dl_bw) { }
++
++void init_dl_bw(struct dl_bw *dl_b) { }
++void init_dl_rq(struct dl_rq *dl_rq) { }
++void init_dl_entity(struct sched_dl_entity *dl_se) { }
++void __init init_sched_dl_class(void) { }
++void sched_init_dl_servers(void) { }
++
++int sched_dl_global_validate(void) { return 0; }
++void sched_dl_do_global(void) { }
++int sched_dl_overflow(struct task_struct *p, int policy,
++		      const struct sched_attr *attr) { return -EPERM; }
++void __setparam_dl(struct task_struct *p, const struct sched_attr *attr) { }
++void __getparam_dl(struct task_struct *p, struct sched_attr *attr) { }
++bool __checkparam_dl(const struct sched_attr *attr) { return false; }
++bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
++{ return false; }
++int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
++				 const struct cpumask *trial) { return 1; }
++s64 dl_scaled_delta_exec(struct rq *rq, struct sched_dl_entity *dl_se,
++			 s64 delta_exec) { return delta_exec; }
++
++void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
++		    dl_server_pick_f pick_task) { }
++void dl_server_start(struct sched_dl_entity *dl_se) { }
++void dl_server_stop(struct sched_dl_entity *dl_se) { }
++void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec) { }
++void dl_server_update_idle(struct sched_dl_entity *dl_se, s64 delta_exec) { }
++void __dl_server_attach_root(struct sched_dl_entity *dl_se, struct rq *rq) { }
++int dl_server_apply_params(struct sched_dl_entity *dl_se, u64 runtime,
++			   u64 period, bool init) { return -EOPNOTSUPP; }
++
++#endif /* CONFIG_SCHED_DEADLINE_CLASS */