2018-05-25 21:34:41

by Arnd Bergmann

Subject: [PATCH, net-next 1/2] bpf: btf: avoid -Wreturn-type warning

gcc warns about a noreturn function possibly returning in
some configurations:

kernel/bpf/btf.c: In function 'env_type_is_resolve_sink':
kernel/bpf/btf.c:729:1: error: control reaches end of non-void function [-Werror=return-type]

Using BUG() instead of BUG_ON() avoids that warning and otherwise
does the exact same thing.

Fixes: eb3f595dab40 ("bpf: btf: Validate type reference")
Signed-off-by: Arnd Bergmann <[email protected]>
---
kernel/bpf/btf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 9cbeabb5aca3..2822a0cf4f48 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -749,7 +749,7 @@ static bool env_type_is_resolve_sink(const struct btf_verifier_env *env,
!btf_type_is_array(next_type) &&
!btf_type_is_struct(next_type);
default:
- BUG_ON(1);
+ BUG();
}
}

--
2.9.0

2018-05-25 21:35:05

by Arnd Bergmann

Subject: [PATCH, net-next 2/2] 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: bae77c5eb5b2 ("bpf: enable stackmap with build_id in nmi context")
Signed-off-by: Arnd Bergmann <[email protected]>
---
kernel/bpf/stackmap.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index b59ace0f0f09..b675a3f3d141 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -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;
--
2.9.0

2018-05-25 21:54:14

by Song Liu

Subject: Re: [PATCH, net-next 1/2] bpf: btf: avoid -Wreturn-type warning

> On May 25, 2018, at 2:33 PM, Arnd Bergmann <[email protected]> wrote:
>
> gcc warns about a noreturn function possibly returning in
> some configurations:
>
> kernel/bpf/btf.c: In function 'env_type_is_resolve_sink':
> kernel/bpf/btf.c:729:1: error: control reaches end of non-void function [-Werror=return-type]
>
> Using BUG() instead of BUG_ON() avoids that warning and otherwise
> does the exact same thing.
>
> Fixes: eb3f595dab40 ("bpf: btf: Validate type reference")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> kernel/bpf/btf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 9cbeabb5aca3..2822a0cf4f48 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -749,7 +749,7 @@ static bool env_type_is_resolve_sink(const struct btf_verifier_env *env,
> !btf_type_is_array(next_type) &&
> !btf_type_is_struct(next_type);
> default:
> - BUG_ON(1);
> + BUG();
> }
> }
>
> --
> 2.9.0
>

Acked-by: Song Liu <[email protected]>

2018-05-25 21:55:24

by Song Liu

Subject: Re: [PATCH, net-next 2/2] bpf: avoid -Wmaybe-uninitialized warning

> On May 25, 2018, at 2:33 PM, Arnd Bergmann <[email protected]> wrote:
>
> 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: bae77c5eb5b2 ("bpf: enable stackmap with build_id in nmi context")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> kernel/bpf/stackmap.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> index b59ace0f0f09..b675a3f3d141 100644
> --- a/kernel/bpf/stackmap.c
> +++ b/kernel/bpf/stackmap.c
> @@ -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;
> --
> 2.9.0
>

Acked-by: Song Liu <[email protected]>

2018-05-27 22:37:26

by Daniel Borkmann

Subject: Re: [PATCH, net-next 1/2] bpf: btf: avoid -Wreturn-type warning

On 05/25/2018 11:33 PM, Arnd Bergmann wrote:
> gcc warns about a noreturn function possibly returning in
> some configurations:
>
> kernel/bpf/btf.c: In function 'env_type_is_resolve_sink':
> kernel/bpf/btf.c:729:1: error: control reaches end of non-void function [-Werror=return-type]
>
> Using BUG() instead of BUG_ON() avoids that warning and otherwise
> does the exact same thing.
>
> Fixes: eb3f595dab40 ("bpf: btf: Validate type reference")
> Signed-off-by: Arnd Bergmann <[email protected]>

Applied to bpf-next, thanks Arnd!

2018-05-27 22:37:53

by Daniel Borkmann

Subject: Re: [PATCH, net-next 2/2] bpf: avoid -Wmaybe-uninitialized warning

On 05/25/2018 11:33 PM, Arnd Bergmann wrote:
> 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: bae77c5eb5b2 ("bpf: enable stackmap with build_id in nmi context")
> Signed-off-by: Arnd Bergmann <[email protected]>

Applied to bpf-next, thanks Arnd!