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| author | Tejun Heo <tj@kernel.org> | 2026-05-31 21:01:47 +0300 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2026-05-31 21:01:47 +0300 |
| commit | a73aa3a5685e648e55787b461f6ee0558db4b0c8 (patch) | |
| tree | d4b2537c71e0f4d8d81200a0a5fb4213f09a4ccc | |
| parent | 6bf8973ddeeec0ead87b0dfe9a3ae6072432e334 (diff) | |
| download | linux-a73aa3a5685e648e55787b461f6ee0558db4b0c8.tar.xz | |
sched_ext: Guard BPF arena helper calls to fix 32-bit build
BPF arena (kernel/bpf/arena.c) is compiled only on MMU && 64BIT, while
SCHED_CLASS_EXT depends on BPF_SYSCALL && BPF_JIT && DEBUG_INFO_BTF with no
64BIT requirement. On a 32-bit arch with a BPF JIT, SCX builds while the
arena helpers are absent, so the cid-form code's unconditional calls to
bpf_prog_arena() and bpf_arena_map_kern_vm_start() fail to link:
build_policy.o: undefined reference to `bpf_prog_arena'
build_policy.o: undefined reference to `bpf_arena_map_kern_vm_start'
Guard the three call sites with the same MMU && 64BIT condition that gates
arena.o. A cid-form scheduler needs a BPF arena, which isn't available on
such builds, so it can't run there regardless. cpu-form schedulers don't
touch the arena and are unaffected.
This is a quick workaround to get past the build errors. A fuller fix may
make the whole cid-form path conditional on the same condition, or drop
32-bit support outright.
Fixes: 0e2819cba977 ("sched_ext: Require an arena for cid-form schedulers")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202605310454.U9iByL2n-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202605310926.APXMc0RJ-lkp@intel.com/
Signed-off-by: Tejun Heo <tj@kernel.org>
| -rw-r--r-- | kernel/sched/ext.c | 14 | ||||
| -rw-r--r-- | kernel/sched/ext_arena.c | 5 |
2 files changed, 16 insertions, 3 deletions
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index 83272acf1763..32ebbc351564 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -622,8 +622,12 @@ static inline void scx_call_op_set_cpumask(struct scx_sched *sch, struct rq *rq, if (scx_is_cid_type()) { struct scx_cmask *kern_va = *this_cpu_ptr(sch->set_cmask_scratch); - unsigned long uaddr = (unsigned long)kern_va - - bpf_arena_map_kern_vm_start(sch->arena_map); + unsigned long uaddr = (unsigned long)kern_va; + + /* arena.o, which defines these, is built only on MMU && 64BIT */ +#if defined(CONFIG_MMU) && defined(CONFIG_64BIT) + uaddr -= bpf_arena_map_kern_vm_start(sch->arena_map); +#endif /* * Build the per-CPU arena cmask and hand BPF the uaddr. Caller * holds the rq lock with IRQs disabled, which makes us the sole @@ -7992,8 +7996,12 @@ struct scx_arena_scan { static int scx_arena_scan_prog(struct bpf_prog *prog, void *data) { struct scx_arena_scan *s = data; - struct bpf_map *arena = bpf_prog_arena(prog); + struct bpf_map *arena = NULL; + /* arena.o, which defines these, is built only on MMU && 64BIT */ +#if defined(CONFIG_MMU) && defined(CONFIG_64BIT) + arena = bpf_prog_arena(prog); +#endif if (!arena) return 0; if (s->arena && s->arena != arena) { diff --git a/kernel/sched/ext_arena.c b/kernel/sched/ext_arena.c index b413e155ba6b..493c2424f842 100644 --- a/kernel/sched/ext_arena.c +++ b/kernel/sched/ext_arena.c @@ -80,7 +80,12 @@ static int scx_arena_grow(struct scx_sched *sch, u32 page_cnt) return -ENOMEM; uaddr32 = (u32)(unsigned long)p; + /* arena.o, which defines these, is built only on MMU && 64BIT */ +#if defined(CONFIG_MMU) && defined(CONFIG_64BIT) kern_vm_start = bpf_arena_map_kern_vm_start(sch->arena_map); +#else + kern_vm_start = 0; +#endif ret = gen_pool_add(sch->arena_pool, kern_vm_start + uaddr32, page_cnt * PAGE_SIZE, NUMA_NO_NODE); |