diff mbox series

[bpf-next,1/3] bpf: make bpf_get_branch_snapshot() architecture-agnostic

Message ID 20240321180501.734779-2-andrii@kernel.org (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series Inline two LBR-related helpers | expand

Checks

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bpf/vmtest-bpf-next-PR success PR summary
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netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
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Commit Message

Andrii Nakryiko March 21, 2024, 6:04 p.m. UTC 
perf_snapshot_branch_stack is set up in an architecture-agnostic way, so
there is no reason for BPF subsystem to keep track of which
architectures do support LBR or not. E.g., it looks like ARM64 might soon
get support for BRBE ([0]), which (with proper integration) should be
possible to utilize using this BPF helper.

perf_snapshot_branch_stack static call will point to
__static_call_return0() by default, which just returns zero, which will
lead to -ENOENT, as expected. So no need to guard anything here.

  [0] https://lore.kernel.org/linux-arm-kernel/20240125094119.2542332-1-anshuman.khandual@arm.com/

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 kernel/trace/bpf_trace.c | 4 ----
 1 file changed, 4 deletions(-)

Comments

Jiri Olsa March 21, 2024, 9:08 p.m. UTC | #1 
On Thu, Mar 21, 2024 at 11:04:59AM -0700, Andrii Nakryiko wrote:
> perf_snapshot_branch_stack is set up in an architecture-agnostic way, so
> there is no reason for BPF subsystem to keep track of which
> architectures do support LBR or not. E.g., it looks like ARM64 might soon
> get support for BRBE ([0]), which (with proper integration) should be
> possible to utilize using this BPF helper.
> 
> perf_snapshot_branch_stack static call will point to
> __static_call_return0() by default, which just returns zero, which will
> lead to -ENOENT, as expected. So no need to guard anything here.
> 
>   [0] https://lore.kernel.org/linux-arm-kernel/20240125094119.2542332-1-anshuman.khandual@arm.com/
> 
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> ---
>  kernel/trace/bpf_trace.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 434e3ece6688..6d000332b17b 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1182,9 +1182,6 @@ static const struct bpf_func_proto bpf_get_attach_cookie_proto_tracing = {
>  
>  BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags)
>  {
> -#ifndef CONFIG_X86
> -	return -ENOENT;
> -#else
>  	static const u32 br_entry_size = sizeof(struct perf_branch_entry);
>  	u32 entry_cnt = size / br_entry_size;
>  
> @@ -1197,7 +1194,6 @@ BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags)
>  		return -ENOENT;
>  
>  	return entry_cnt * br_entry_size;
> -#endif
>  }
>  
>  static const struct bpf_func_proto bpf_get_branch_snapshot_proto = {
> -- 
> 2.43.0
> 
>
diff mbox series

Patch

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 434e3ece6688..6d000332b17b 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1182,9 +1182,6 @@  static const struct bpf_func_proto bpf_get_attach_cookie_proto_tracing = {
 
 BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags)
 {
-#ifndef CONFIG_X86
-	return -ENOENT;
-#else
 	static const u32 br_entry_size = sizeof(struct perf_branch_entry);
 	u32 entry_cnt = size / br_entry_size;
 
@@ -1197,7 +1194,6 @@  BPF_CALL_3(bpf_get_branch_snapshot, void *, buf, u32, size, u64, flags)
 		return -ENOENT;
 
 	return entry_cnt * br_entry_size;
-#endif
 }
 
 static const struct bpf_func_proto bpf_get_branch_snapshot_proto = {