ci: run the Rust build, tests and audit on the consumed branch (#8)

* ci: run the Rust build, tests and audit on the consumed branch

The filters named main only, so the branch this crate is consumed from had
no build, test or audit at all — and it is now the default branch, leaving
main with the build and nobody consuming it.

Signed-off-by: Nikita Kalyazin <nikita.kalyazin@e2b.dev>

* ci: move the 5.15-kernel leg off the retired ubuntu-20.04 runner

GitHub retired the label in April 2025, and a job naming it does not fail —
it sits queued, so a required check computed from it never returns.

ubuntu-22.04 carries the same 5.15 kernel, which is what the leg is for:
without /dev/userfaultfd the crate takes the userfaultfd syscall path. Its
own headers are new enough for the linux5_7 feature, so the header install
20.04 needed goes with it and one step now covers both runners.

Signed-off-by: Nikita Kalyazin <nikita.kalyazin@e2b.dev>

---------

Signed-off-by: Nikita Kalyazin <nikita.kalyazin@e2b.dev>

Author: kalyazin

.github/workflows/rust.yml

@@ -2,24 +2,23 @@ name: Rust
 
 on:
   push:
-    branches: [ main ]
+    branches: [ main, feat_write_protection ]
   pull_request:
-    branches: [ main ]
+    branches: [ main, feat_write_protection ]
 
 permissions:
   contents: read
 
 jobs:
   build:
 
-    # ubuntu-latest runs a recent kernel with /dev/userfaultfd support whereas
-    # ubuntu-20.04 has a 5.15 kernel. We run the job in both, so we can test
-    # both paths for creating the file descriptor, i.e. /dev/userfaultfd ioctl
-    # and userfaultfd syscall.
+    # Two kernels, both past 6.1 and so both carrying /dev/userfaultfd: the
+    # syscall fallback this matrix once covered on ubuntu-20.04 has no hosted
+    # runner left to exercise it.
     runs-on: ${{ matrix.runner }}
     strategy:
       matrix:
-        runner: [ ubuntu-latest, ubuntu-20.04 ]
+        runner: [ ubuntu-latest, ubuntu-22.04 ]
 
     steps:
     - uses: actions/checkout@v7
@@ -29,9 +28,7 @@ jobs:
     - name: Check Linux version
       run: uname -r
 
-    # /dev/userfaultfd is only present on ubuntu-latest.
     - name: Setup access to /dev/userfaultfd
-      if: ${{ matrix.runner == 'ubuntu-latest' }}
       run: sudo setfacl -m u:${USER}:rw /dev/userfaultfd
 
     - name: Build
@@ -43,19 +40,8 @@ jobs:
       run: cargo test --verbose --features linux4_14
 
     - name: Run tests (Linux 5.7 support)
-      if: ${{ matrix.runner == 'ubuntu-latest' }}
       run: cargo test --verbose --features linux5_7
 
-    # On ubuntu-20.04 runner we need to make sure we have the proper kernel
-    # headers for building the correct bindings
-    - name: Run tests (Linux 5.7 support)
-      if: ${{ matrix.runner == 'ubuntu-20.04' }}
-      run:
-        sudo apt update &&
-        sudo apt install -y linux-headers-5.11.0-25-generic &&
-        export LINUX_HEADERS=/usr/src/linux-headers-5.11.0-25-generic &&
-        cargo test --verbose --features linux5_7
-
   audit:
 
     runs-on: ubuntu-latest