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selftests/bpf: Check faultable stack helper contexts

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Add verifier coverage for the sleepable bpf_get_stack() and
bpf_get_task_stack() implementations. Call each helper while preemption is
disabled and require the verifier to reject it as sleepable.

Both programs load when the prototypes lack might_sleep, so the
expected-failure tests fail. Keep success controls outside the
non-preemptible region to ensure ordinary calls from sleepable uprobes
remain valid.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260903214758.2727663-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi 2026-09-03 23:47:52 +02:00 committed by Alexei Starovoitov
parent 9d02927fdf
commit 1ba0d0d8b6
1 changed files with 52 additions and 0 deletions
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52
tools/testing/selftests/bpf/progs/preempt_lock.c
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@ -115,6 +115,58 @@ int preempt_sleepable_helper(void *ctx)
return 0;
}
SEC("?uprobe.s")
__failure __msg("sleepable helper bpf_get_stack#")
int preempt_sleepable_get_stack(struct pt_regs *ctx)
{
struct bpf_stack_build_id stack;
bpf_preempt_disable();
bpf_get_stack(ctx, &stack, sizeof(stack),
BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
bpf_preempt_enable();
return 0;
}
SEC("?uprobe.s")
__failure __msg("sleepable helper bpf_get_task_stack#")
int preempt_sleepable_get_task_stack(void *ctx)
{
struct bpf_stack_build_id stack;
struct task_struct *task;
task = bpf_get_current_task_btf();
bpf_preempt_disable();
bpf_get_task_stack(task, &stack, sizeof(stack),
BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
bpf_preempt_enable();
return 0;
}
SEC("?uprobe.s")
__success
int sleepable_get_stack(struct pt_regs *ctx)
{
struct bpf_stack_build_id stack;
bpf_get_stack(ctx, &stack, sizeof(stack),
BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
return 0;
}
SEC("?uprobe.s")
__success
int sleepable_get_task_stack(void *ctx)
{
struct bpf_stack_build_id stack;
struct task_struct *task;
task = bpf_get_current_task_btf();
bpf_get_task_stack(task, &stack, sizeof(stack),
BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
return 0;
}
SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
__failure __msg("kernel func bpf_copy_from_user_str is sleepable within non-preemptible region")
int preempt_sleepable_kfunc(void *ctx)