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bpf: Introduce jit_required flag and remove bpf_prog_has_kfunc_call()

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Introduce a 'jit_required' bitfield flag in struct bpf_prog to track
whether a BPF program strictly requires the JIT compiler to run. This
prevents a dangerous runtime fallback to the interpreter for features
that are only implemented in the JIT compiler.

Currently, bpf_prog_has_kfunc_call() is used only for kernel function
calls, replace the kfunc-specific helper with the new 'jit_required'
flag. This makes it easy to support other JIT-only BPF features, such
as inlined helpers.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Suggested-by: KaFai Wan <kafai.wan@linux.dev>
Suggested-by: Leon Hwang <leon.hwang@linux.dev>
Acked-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
This commit is contained in:
Tiezhu Yang
2026-07-08 18:18:05 +08:00
committed by Eduard Zingerman
parent 47b079e211
commit 9a6df65d5c
4 changed files with 8 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/bpf.h
View File

@@ -1864,8 +1864,9 @@ struct bpf_prog_aux {
struct bpf_prog {
u16 pages; /* Number of allocated pages */
u16 jited:1, /* Is our filter JIT'ed? */
u32 jited:1, /* Is our filter JIT'ed? */
jit_requested:1,/* archs need to JIT the prog */
jit_required:1, /* program strictly requires JIT compiler */
gpl_compatible:1, /* Is filter GPL compatible? */
cb_access:1, /* Is control block accessed? */
dst_needed:1, /* Do we need dst entry? */
@@ -3169,7 +3170,6 @@ const struct bpf_func_proto *bpf_base_func_proto(enum bpf_func_id func_id,
const struct bpf_prog *prog);
void bpf_task_storage_free(struct task_struct *task);
void bpf_cgrp_storage_free(struct cgroup *cgroup);
bool bpf_prog_has_kfunc_call(const struct bpf_prog *prog);
const struct btf_func_model *
bpf_jit_find_kfunc_model(const struct bpf_prog *prog,
const struct bpf_insn *insn);
@@ -3508,11 +3508,6 @@ static inline void bpf_task_storage_free(struct task_struct *task)
{
}
static inline bool bpf_prog_has_kfunc_call(const struct bpf_prog *prog)
{
return false;
}
static inline const struct btf_func_model *
bpf_jit_find_kfunc_model(const struct bpf_prog *prog,
const struct bpf_insn *insn)

7
kernel/bpf/core.c
View File

@@ -126,6 +126,7 @@ struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flag
fp->aux->main_prog_aux = aux;
fp->aux->prog = fp;
fp->jit_requested = ebpf_jit_enabled();
fp->jit_required = IS_ENABLED(CONFIG_BPF_JIT_ALWAYS_ON);
fp->blinding_requested = bpf_jit_blinding_enabled(fp);
#ifdef CONFIG_CGROUP_BPF
aux->cgroup_atype = CGROUP_BPF_ATTACH_TYPE_INVALID;
@@ -2670,15 +2671,11 @@ struct bpf_prog *__bpf_prog_select_runtime(struct bpf_verifier_env *env, struct
/* In case of BPF to BPF calls, verifier did all the prep
* work with regards to JITing, etc.
*/
bool jit_needed = false;
bool jit_needed = fp->jit_required;
if (fp->bpf_func)
goto finalize;
if (IS_ENABLED(CONFIG_BPF_JIT_ALWAYS_ON) ||
bpf_prog_has_kfunc_call(fp))
jit_needed = true;
if (!bpf_prog_select_interpreter(fp))
jit_needed = true;

5
kernel/bpf/fixups.c
View File

@@ -1378,7 +1378,6 @@ int bpf_fixup_call_args(struct bpf_verifier_env *env)
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
struct bpf_prog *prog = env->prog;
struct bpf_insn *insn = prog->insnsi;
bool has_kfunc_call = bpf_prog_has_kfunc_call(prog);
int depth;
#endif
int i, err = 0;
@@ -1404,8 +1403,8 @@ int bpf_fixup_call_args(struct bpf_verifier_env *env)
return err;
}
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
if (has_kfunc_call) {
verbose(env, "calling kernel functions are not allowed in non-JITed programs\n");
if (prog->jit_required) {
verbose(env, "program requires BPF JIT compiler but it is not available\n");
return -EINVAL;
}
for (i = 0; i < env->subprog_cnt; i++) {

7
kernel/bpf/verifier.c
View File

@@ -2780,6 +2780,8 @@ int bpf_add_kfunc_call(struct bpf_verifier_env *env, u32 func_id, u16 offset)
prog_aux->kfunc_tab = tab;
}
env->prog->jit_required = 1;
/* func_id == 0 is always invalid, but instead of returning an error, be
* conservative and wait until the code elimination pass before returning
* error, so that invalid calls that get pruned out can be in BPF programs
@@ -2834,11 +2836,6 @@ int bpf_add_kfunc_call(struct bpf_verifier_env *env, u32 func_id, u16 offset)
return 0;
}
bool bpf_prog_has_kfunc_call(const struct bpf_prog *prog)
{
return !!prog->aux->kfunc_tab;
}
static int add_subprog_and_kfunc(struct bpf_verifier_env *env)
{
struct bpf_subprog_info *subprog = env->subprog_info;