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Make gRPC frame pos deterministic for eBPF verifier #574

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merged 2 commits into from
Dec 28, 2023
Merged

Make gRPC frame pos deterministic for eBPF verifier #574

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c74eb1f
adjust the frame pos for grpc server in a deterministic way, so the v…
RonFed Dec 28, 2023
8706cd0
add __always_inline
RonFed Dec 28, 2023
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4 changes: 2 additions & 2 deletions internal/include/arguments.h
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@
// Injected in init
volatile const bool is_registers_abi;

void *get_argument_by_reg(struct pt_regs *ctx, int index)
void __always_inline *get_argument_by_reg(struct pt_regs *ctx, int index)
{
switch (index)
{
Expand All @@ -50,7 +50,7 @@ void *get_argument_by_reg(struct pt_regs *ctx, int index)
}
}

void *get_argument_by_stack(struct pt_regs *ctx, int index)
void __always_inline *get_argument_by_stack(struct pt_regs *ctx, int index)
{
void *ptr = 0;
bpf_probe_read(&ptr, sizeof(ptr), (void *)(PT_REGS_SP(ctx) + (index * 8)));
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8 changes: 7 additions & 1 deletion internal/pkg/instrumentation/bpf/google.golang.org/grpc/server/bpf/probe.bpf.c
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Expand Up @@ -67,7 +67,7 @@ volatile const u64 frame_fields_pos;
volatile const u64 frame_stream_id_pod;
volatile const u64 stream_id_pos;
volatile const u64 stream_ctx_pos;
volatile const u64 frame_pos;
volatile const bool is_new_frame_pos;

// This instrumentation attaches uprobe to the following function:
// func (s *Server) handleStream(t transport.ServerTransport, stream *transport.Stream, trInfo *traceInfo)
Expand Down Expand Up @@ -124,9 +124,15 @@ int uprobe_server_handleStream(struct pt_regs *ctx)
UPROBE_RETURN(server_handleStream, struct grpc_request_t, grpc_events, events, 4, stream_ctx_pos, false)

// func (d *http2Server) operateHeader(frame *http2.MetaHeadersFrame) error
// for version 1.60 and above:
// func (t *http2Server) operateHeaders(ctx context.Context, frame *http2.MetaHeadersFrame, handle func(*Stream)) error
SEC("uprobe/http2Server_operateHeader")
int uprobe_http2Server_operateHeader(struct pt_regs *ctx)
{
u64 frame_pos = 2;
if (is_new_frame_pos) {
frame_pos = 4;
}
void *frame_ptr = get_argument(ctx, frame_pos);
struct go_slice header_fields = {};
bpf_probe_read(&header_fields, sizeof(header_fields), (void *)(frame_ptr + frame_fields_pos));
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6 changes: 1 addition & 5 deletions internal/pkg/instrumentation/bpf/google.golang.org/grpc/server/probe.go
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Expand Up @@ -109,11 +109,7 @@ func (c framePosConst) InjectOption(td *process.TargetDetails) (inject.Option, e
return nil, fmt.Errorf("unknown module version: %s", pkg)
}

var pos uint64 = 2
if ver.GreaterThanOrEqual(paramChangeVer) {
pos = 4
}
return inject.WithKeyValue("frame_pos", pos), nil
return inject.WithKeyValue("is_new_frame_pos", ver.GreaterThanOrEqual(paramChangeVer)), nil
}

func uprobeHandleStream(name string, exec *link.Executable, target *process.TargetDetails, obj *bpfObjects) ([]link.Link, error) {
Expand Down
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