feat: strncmp implementation for old kernels

exein-io · Feb 27, 2024 · 02c0213 · 02c0213
1 parent 1e92ea1
commit 02c0213
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Showing 2 changed files with 41 additions and 4 deletions.
diff --git a/crates/bpf-builder/include/strncmp.bpf.h b/crates/bpf-builder/include/strncmp.bpf.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#pragma once
+
+#include "vmlinux.h"
+#include "common.bpf.h"
+
+#define STRNCMP(s1, s1_sz, s2)                                    \
+    ({                                                            \
+        int result;                                               \
+        if (LINUX_KERNEL_VERSION >= KERNEL_VERSION(5, 17, 0))     \
+        {                                                         \
+            result = bpf_strncmp(s1, s1_sz, s2);                  \
+        }                                                         \
+        else                                                      \
+        {                                                         \
+                                                                  \
+            char *__cs = (s1);                                    \
+            char *__ct = (s2);                                    \
+            unsigned char __c1, __c2;                             \
+            _Pragma("unroll") for (__u32 i = (s1_sz); i > 0; i--) \
+            {                                                     \
+                __c1 = *__cs++;                                   \
+                __c2 = *__ct++;                                   \
+                if (__c1 != __c2)                                 \
+                {                                                 \
+                    result = __c1 < __c2 ? -1 : 1;                \
+                    break;                                        \
+                }                                                 \
+                if (!__c1)                                        \
+                {                                                 \
+                    result = 0;                                   \
+                    break;                                        \
+                }                                                 \
+            }                                                     \
+        }                                                         \
+        result;                                                   \
+    })
diff --git a/crates/modules/process-monitor/probes.bpf.c b/crates/modules/process-monitor/probes.bpf.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
 #include "bpf/bpf_core_read.h"
 #include "common.bpf.h"
-
+#include "strncmp.bpf.h"
 #include "bpf/bpf_helpers.h"
 #include "buffer.bpf.h"
 #include "get_path.bpf.h"
@@ -189,7 +189,7 @@ static __always_inline int get_container_info(struct task_struct *cur_tsk, char
   }
 
   // Docker case
-  if (bpf_strncmp(buf, 7, "docker-") == 0)
+  if (STRNCMP(buf, 7, "docker-") == 0)
   {
     *offset = 7;
     return DOCKER_CONTAINER_ENGINE;
@@ -199,7 +199,7 @@ static __always_inline int get_container_info(struct task_struct *cur_tsk, char
   //
   // the check for NULL character is needed to avoid collisions with
   // `containerd-` prefixed cgroup name
-  if (bpf_strncmp(buf, 9, "container") == 0 && buf[9] == '\0')
+  if (STRNCMP(buf, 9, "container") == 0 && buf[9] == '\0')
   {
 
     const char *parent_name = BPF_CORE_READ(cur_tsk, cgroups, subsys[cgrp_id], cgroup, kn, parent, name);
@@ -210,7 +210,7 @@ static __always_inline int get_container_info(struct task_struct *cur_tsk, char
       return FAILED_READ_PARENT_CGROUP_NAME;
     }
 
-    if (bpf_strncmp(buf, 7, "libpod-") == 0)
+    if (STRNCMP(buf, 7, "libpod-") == 0)
     {
       *offset = 7;
       return PODMAN_CONTAINER_ENGINE;