Update hyperlight-guest-tracing crate to conditionally enable traces at compile time (#752)

* [trace] Add check for empty message to trace macro

Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

* [trace] move tracing logic inside tracing module

- this helps with later conditionally compiling only the tracing code
depending on a feature

Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

* [trace] add 'trace' feature to guest tracing crates

- This allows the use of the 'hyperlight-guest-tracing'
  without having the tracing enabled
- Now the user can select at compile time whether the
  macros enable tracing or not
- Before this change, the crate using the macros from
  hyperlight-guest-tracing-macro needed to define a features
  called 'trace_guest' because the generated code would gate
  everything with that feature
- The change makes the generation of code dependent on the
 'trace' feature
- Some of the variables used in the macros were prefixed with
  an '_' to avoid warnings when the 'trace' feature is not set

Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

* [trace] move macros tests to the tracing crate

- This is needed for the tests to pass because the macros
use 'hyperlight_guest_tracing::' which cannot be imported by
'hyperlight_guest_tracing_macro' bacause it would create a
circular dependency.
- The caveat is that when using 'hyperlight_guest_tracing_macro'
one needs to have as a dependency 'hyperlight_guest_tracing'
also

Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

* update guests to use the tracing crate to intrument functions

Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

---------

Signed-off-by: Doru Blânzeanu <dblnz@pm.me>

Author: dblnz

src/hyperlight_guest/Cargo.toml

@@ -15,8 +15,8 @@ Provides only the essential building blocks for interacting with the host enviro
 anyhow = { version = "1.0.98", default-features = false }
 serde_json = { version = "1.0", default-features = false, features = ["alloc"] }
 hyperlight-common = { workspace = true }
-hyperlight-guest-tracing = { workspace = true }
+hyperlight-guest-tracing = { workspace = true, default-features = false }
 
 [features]
 default = []
-trace_guest = []
+trace_guest = ["hyperlight-guest-tracing/trace"]

src/hyperlight_guest_bin/Cargo.toml

@@ -17,13 +17,13 @@ and third-party code used by our C-API needed to build a native hyperlight-guest
 default = ["libc", "printf"]
 libc = [] # compile musl libc
 printf = [ "libc" ] # compile printf
-trace_guest = ["hyperlight-common/trace_guest", "hyperlight-guest/trace_guest"]
+trace_guest = ["hyperlight-common/trace_guest", "hyperlight-guest/trace_guest", "hyperlight-guest-tracing/trace"]
 mem_profile = ["hyperlight-common/unwind_guest","hyperlight-common/mem_profile"]
 
 [dependencies]
 hyperlight-guest = { workspace = true, default-features = false }
 hyperlight-common = { workspace = true, default-features = false }
-hyperlight-guest-tracing = { workspace = true }
+hyperlight-guest-tracing = { workspace = true, default-features = false }
 buddy_system_allocator = "0.11.0"
 log = { version = "0.4", default-features = false }
 spin = "0.10.0"

src/hyperlight_guest_tracing/Cargo.toml

@@ -10,9 +10,13 @@ readme.workspace = true
 description = """Provides the tracing functionality for the hyperlight guest."""
 
 [dependencies]
-hyperlight-common = { workspace = true, default-features = false, features = ["trace_guest"] }
+hyperlight-common = { workspace = true, default-features = false }
 hyperlight-guest-tracing-macro = { workspace = true }
 spin = "0.10.0"
 
 [lints]
 workspace = true
+
+[features]
+default = []
+trace = [ "hyperlight-guest-tracing-macro/trace", "hyperlight-common/trace_guest" ]