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Arm64 atomic inc fix #10223

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Arm64 atomic inc fix #10223

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a99a176
bpf: move recursion detection logic to helpers
puranjaymohan Nov 6, 2025
7ea535b
bpf: Optimize recursion detection by not using atomics
puranjaymohan Nov 4, 2025
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27 changes: 26 additions & 1 deletion include/linux/bpf.h
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@
#include <linux/static_call.h>
#include <linux/memcontrol.h>
#include <linux/cfi.h>
#include <linux/unaligned.h>
#include <asm/rqspinlock.h>

struct bpf_verifier_env;
Expand Down Expand Up @@ -1729,6 +1730,8 @@ struct bpf_prog_aux {
struct bpf_stream stream[2];
};

#define BPF_NR_CONTEXTS 4 /* normal, softirq, hardirq, NMI */

struct bpf_prog {
u16 pages; /* Number of allocated pages */
u16 jited:1, /* Is our filter JIT'ed? */
Expand All @@ -1755,7 +1758,7 @@ struct bpf_prog {
u8 tag[BPF_TAG_SIZE];
};
struct bpf_prog_stats __percpu *stats;
int __percpu *active;
u8 __percpu *active; /* u8[BPF_NR_CONTEXTS] for rerecursion protection */
unsigned int (*bpf_func)(const void *ctx,
const struct bpf_insn *insn);
struct bpf_prog_aux *aux; /* Auxiliary fields */
Expand Down Expand Up @@ -1985,6 +1988,28 @@ struct bpf_struct_ops_common_value {
enum bpf_struct_ops_state state;
};

static inline bool bpf_prog_get_recursion_context(struct bpf_prog *prog)
{
u8 rctx = interrupt_context_level();
u8 *active = this_cpu_ptr(prog->active);

active[rctx]++;
barrier();
if (get_unaligned_le32(active) != BIT(rctx * 8))
return false;

return true;
}

static inline void bpf_prog_put_recursion_context(struct bpf_prog *prog)
{
u8 rctx = interrupt_context_level();
u8 *active = this_cpu_ptr(prog->active);

barrier();
active[rctx]--;
}

#if defined(CONFIG_BPF_JIT) && defined(CONFIG_BPF_SYSCALL)
/* This macro helps developer to register a struct_ops type and generate
* type information correctly. Developers should use this macro to register
Expand Down
3 changes: 2 additions & 1 deletion kernel/bpf/core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -112,7 +112,8 @@ struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flag
vfree(fp);
return NULL;
}
fp->active = alloc_percpu_gfp(int, bpf_memcg_flags(GFP_KERNEL | gfp_extra_flags));
fp->active = __alloc_percpu_gfp(sizeof(u8[BPF_NR_CONTEXTS]), 8,
bpf_memcg_flags(GFP_KERNEL | gfp_extra_flags));
if (!fp->active) {
vfree(fp);
kfree(aux);
Expand Down
8 changes: 4 additions & 4 deletions kernel/bpf/trampoline.c
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Original file line number Diff line number Diff line change
Expand Up @@ -903,7 +903,7 @@ static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tram

run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);

if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
if (unlikely(!bpf_prog_get_recursion_context(prog))) {
bpf_prog_inc_misses_counter(prog);
if (prog->aux->recursion_detected)
prog->aux->recursion_detected(prog);
Expand Down Expand Up @@ -947,7 +947,7 @@ static void notrace __bpf_prog_exit_recur(struct bpf_prog *prog, u64 start,
bpf_reset_run_ctx(run_ctx->saved_run_ctx);

update_prog_stats(prog, start);
this_cpu_dec(*(prog->active));
bpf_prog_put_recursion_context(prog);
rcu_read_unlock_migrate();
}

Expand Down Expand Up @@ -983,7 +983,7 @@ u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,

run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);

if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
if (unlikely(!bpf_prog_get_recursion_context(prog))) {
bpf_prog_inc_misses_counter(prog);
if (prog->aux->recursion_detected)
prog->aux->recursion_detected(prog);
Expand All @@ -998,7 +998,7 @@ void notrace __bpf_prog_exit_sleepable_recur(struct bpf_prog *prog, u64 start,
bpf_reset_run_ctx(run_ctx->saved_run_ctx);

update_prog_stats(prog, start);
this_cpu_dec(*(prog->active));
bpf_prog_put_recursion_context(prog);
migrate_enable();
rcu_read_unlock_trace();
}
Expand Down
4 changes: 2 additions & 2 deletions kernel/trace/bpf_trace.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2063,7 +2063,7 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args)
struct bpf_trace_run_ctx run_ctx;

cant_sleep();
if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
if (unlikely(!bpf_prog_get_recursion_context(prog))) {
bpf_prog_inc_misses_counter(prog);
goto out;
}
Expand All @@ -2077,7 +2077,7 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args)

bpf_reset_run_ctx(old_run_ctx);
out:
this_cpu_dec(*(prog->active));
bpf_prog_put_recursion_context(prog);
}

#define UNPACK(...) __VA_ARGS__
Expand Down
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