Merge pull request #1733 from pchaigno/fix-probesetter-memberexpr

Fix dereference replacements for structure members

src/cc/frontends/clang/b_frontend_action.cc

@@ -105,6 +105,13 @@ class ProbeChecker : public RecursiveASTVisitor<ProbeChecker> {
     }
     return false;
   }
+  bool VisitMemberExpr(MemberExpr *M) {
+    if (ptregs_.find(M->getMemberDecl()) != ptregs_.end()) {
+      needs_probe_ = true;
+      return false;
+    }
+    return true;
+  }
   bool VisitDeclRefExpr(DeclRefExpr *E) {
     if (ptregs_.find(E->getDecl()) != ptregs_.end())
       needs_probe_ = true;
@@ -126,6 +133,10 @@ class ProbeSetter : public RecursiveASTVisitor<ProbeSetter> {
     ptregs_->insert(E->getDecl());
     return true;
   }
+  bool VisitMemberExpr(MemberExpr *M) {
+    ptregs_->insert(M->getMemberDecl());
+    return false;
+  }
  private:
   set<Decl *> *ptregs_;
 };
@@ -231,11 +242,6 @@ bool ProbeVisitor::VisitUnaryOperator(UnaryOperator *E) {
 bool ProbeVisitor::VisitMemberExpr(MemberExpr *E) {
   if (memb_visited_.find(E) != memb_visited_.end()) return true;
 
-  // Checks to see if the expression references something that needs to be run
-  // through bpf_probe_read.
-  if (!ProbeChecker(E, ptregs_).needs_probe())
-    return true;
-
   Expr *base;
   SourceLocation rhs_start, member;
   bool found = false;
@@ -255,6 +261,12 @@ bool ProbeVisitor::VisitMemberExpr(MemberExpr *E) {
     error(base->getLocEnd(), "internal error: MemberLoc is invalid while preparing probe rewrite");
     return false;
   }
+
+  // Checks to see if the expression references something that needs to be run
+  // through bpf_probe_read.
+  if (!ProbeChecker(base, ptregs_).needs_probe())
+    return true;
+
   string rhs = rewriter_.getRewrittenText(expansionRange(SourceRange(rhs_start, E->getLocEnd())));
   string base_type = base->getType()->getPointeeType().getAsString();
   string pre, post;

tests/python/test_clang.py

@@ -343,6 +343,32 @@ int kprobe____kmalloc(struct pt_regs *ctx, size_t size) {
     return 0;
 }""")
 
+    def test_probe_simple_member_assign(self):
+        b = BPF(text="""
+#include <uapi/linux/ptrace.h>
+#include <linux/netdevice.h>
+struct leaf { void *ptr; };
+int test(struct pt_regs *ctx, struct sk_buff *skb) {
+    struct leaf l = {};
+    struct leaf *lp = &l;
+    lp->ptr = skb;
+    return 0;
+}""")
+        b.load_func("test", BPF.KPROBE)
+
+    def test_probe_member_expr(self):
+        b = BPF(text="""
+#include <uapi/linux/ptrace.h>
+#include <linux/netdevice.h>
+struct leaf { struct sk_buff *ptr; };
+int test(struct pt_regs *ctx, struct sk_buff *skb) {
+    struct leaf l = {};
+    struct leaf *lp = &l;
+    lp->ptr = skb;
+    return lp->ptr->priority;
+}""")
+        b.load_func("test", BPF.KPROBE)
+
     def test_unop_probe_read(self):
         text = """
 #include <linux/blkdev.h>

tools/btrfsslower.py

@@ -224,8 +224,8 @@ static int trace_return(struct pt_regs *ctx, int type)
     // workaround (rewriter should handle file to d_name in one step):
     struct dentry *de = NULL;
     struct qstr qs = {};
-    bpf_probe_read(&de, sizeof(de), &valp->fp->f_path.dentry);
-    bpf_probe_read(&qs, sizeof(qs), (void *)&de->d_name);
+    de = valp->fp->f_path.dentry;
+    qs = de->d_name;
     if (qs.len == 0)
         return 0;
     bpf_probe_read(&data.file, sizeof(data.file), (void *)qs.name);

tools/ext4slower.py

@@ -219,8 +219,8 @@ static int trace_return(struct pt_regs *ctx, int type)
     // workaround (rewriter should handle file to d_name in one step):
     struct dentry *de = NULL;
     struct qstr qs = {};
-    bpf_probe_read(&de, sizeof(de), &valp->fp->f_path.dentry);
-    bpf_probe_read(&qs, sizeof(qs), (void *)&de->d_name);
+    de = valp->fp->f_path.dentry;
+    qs = de->d_name;
     if (qs.len == 0)
         return 0;
     bpf_probe_read(&data.file, sizeof(data.file), (void *)qs.name);