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bpf: Allow fall back to interpreter for programs with stack size <= 512 #5681

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bpf: Allow fall back to interpreter for programs with stack size <= 512 #5681

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12 changes: 7 additions & 5 deletions kernel/bpf/core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2366,8 +2366,8 @@ static unsigned int __bpf_prog_ret0_warn(const void *ctx,
const struct bpf_insn *insn)
{
/* If this handler ever gets executed, then BPF_JIT_ALWAYS_ON
* is not working properly, or interpreter is being used when
* prog->jit_requested is not 0, so warn about it!
* or may_goto may cause stack size > 512 is not working properly,
* so warn about it!
*/
WARN_ON_ONCE(1);
return 0;
Expand Down Expand Up @@ -2478,10 +2478,10 @@ static void bpf_prog_select_func(struct bpf_prog *fp)
* But for non-JITed programs, we don't need bpf_func, so no bounds
* check needed.
*/
if (!fp->jit_requested &&
!WARN_ON_ONCE(idx >= ARRAY_SIZE(interpreters))) {
if (idx < ARRAY_SIZE(interpreters)) {
fp->bpf_func = interpreters[idx];
} else {
WARN_ON_ONCE(!fp->jit_requested);
fp->bpf_func = __bpf_prog_ret0_warn;
}
#else
Expand All @@ -2505,7 +2505,7 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
/* In case of BPF to BPF calls, verifier did all the prep
* work with regards to JITing, etc.
*/
bool jit_needed = fp->jit_requested;
bool jit_needed = false;

if (fp->bpf_func)
goto finalize;
Expand All @@ -2515,6 +2515,8 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
jit_needed = true;

bpf_prog_select_func(fp);
if (fp->bpf_func == __bpf_prog_ret0_warn)
jit_needed = true;

/* eBPF JITs can rewrite the program in case constant
* blinding is active. However, in case of error during
Expand Down
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