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bpf: avoid -Wmaybe-uninitialized warning 

The stack_map_get_build_id_offset() function is too long for gcc to track
whether 'work' may or may not be initialized at the end of it, leading
to a false-positive warning:

kernel/bpf/stackmap.c: In function 'stack_map_get_build_id_offset':
kernel/bpf/stackmap.c:334:13: error: 'work' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This removes the 'in_nmi_ctx' flag and uses the state of that variable
itself to see if it got initialized.

Fixes: bae77c5eb5 ("bpf: enable stackmap with build_id in nmi context")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Arnd Bergmann 2018-05-25 23:33:20 +02:00 committed by Daniel Borkmann
parent 53c8036cb7
commit dc3b8ae9d2
1 changed files with 3 additions and 4 deletions
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7
kernel/bpf/stackmap.c
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@ -285,11 +285,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
{
int i;
struct vm_area_struct *vma;
bool in_nmi_ctx = in_nmi();
bool irq_work_busy = false;
struct stack_map_irq_work *work;
struct stack_map_irq_work *work = NULL;
if (in_nmi_ctx) {
if (in_nmi()) {
work = this_cpu_ptr(&up_read_work);
if (work->irq_work.flags & IRQ_WORK_BUSY)
/* cannot queue more up_read, fallback */
@ -328,7 +327,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
}
if (!in_nmi_ctx) {
if (!work) {
up_read(&current->mm->mmap_sem);
} else {
work->sem = &current->mm->mmap_sem;