This patch fixes the BPF backend to not generate `exit' (return)
instructions in epilogues of functions that are declared as naked via
the corresponding compiler attribute. Having extra exit instructions
upsets the kernel BPF verifier.
Tested in bpf-unknown-none target in x86_64-linux-gnu host.
gcc/ChangeLog
* config/bpf/bpf.cc (bpf_expand_epilogue): Do not emit a return
instruction in naked function epilogues.
gcc/testsuite/ChangeLog
* gcc.target/bpf/naked-1.c: Update test to not expect an exit
instruction in naked function.
* gcc.target/bpf/naked-2.c: New test.
---
gcc/config/bpf/bpf.cc | 5 ++---
gcc/testsuite/gcc.target/bpf/naked-1.c | 1 -
gcc/testsuite/gcc.target/bpf/naked-2.c | 10 ++++++++++
3 files changed, 12 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/bpf/naked-2.c
diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
index 9af1728d852..d6ca47eeecb 100644
--- a/gcc/config/bpf/bpf.cc
+++ b/gcc/config/bpf/bpf.cc
@@ -420,9 +420,8 @@ bpf_expand_epilogue (void)
/* See note in bpf_expand_prologue for an explanation on why we are
not restoring callee-saved registers in BPF. */
- /* If we ever need to do anything else than just generating a return
- instruction here, please mind the `naked' function attribute. */
-
+ if (lookup_attribute ("naked", DECL_ATTRIBUTES (cfun->decl)) != NULL_TREE)
+ return;
emit_jump_insn (gen_exit ());
}
diff --git a/gcc/testsuite/gcc.target/bpf/naked-1.c
b/gcc/testsuite/gcc.target/bpf/naked-1.c
index cbbc4c51697..dc8ac2619cc 100644
--- a/gcc/testsuite/gcc.target/bpf/naked-1.c
+++ b/gcc/testsuite/gcc.target/bpf/naked-1.c
@@ -9,4 +9,3 @@ int __attribute__((naked)) foo()
__asm__ volatile ("@ naked");
}
/* { dg-final { scan-assembler "\t@ naked" } } */
-/* { dg-final { scan-assembler "\texit\n" } } */
diff --git a/gcc/testsuite/gcc.target/bpf/naked-2.c
b/gcc/testsuite/gcc.target/bpf/naked-2.c
new file mode 100644
index 00000000000..25aebf84755
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/naked-2.c
@@ -0,0 +1,10 @@
+/* Verify that __attribute__((naked)) produces functions without implicit
+ `exit' instructions in the epilogue. */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+int __attribute__((naked)) foo()
+{
+ __asm__ volatile ("exit");
+}
+/* { dg-final { scan-assembler-times "\texit" 1 } } */
--
2.30.2
