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| author | Jose E. Marchesi <jose.marchesi@oracle.com> | 2024-01-29 17:47:00 +0100 |
|---|---|---|
| committer | Jose E. Marchesi <jose.marchesi@oracle.com> | 2024-01-29 18:51:45 +0100 |
| commit | 1959aeee1e0e0b5eca12178444ba2f28c0ae558f (patch) | |
| tree | 8034dba31a0778c30910d079d4d6be4def3a2607 | |
| parent | 25cd22bf02d55d0778ee7b883eb698204a120a16 (diff) | |
| download | gcc-1959aeee1e0e0b5eca12178444ba2f28c0ae558f.zip gcc-1959aeee1e0e0b5eca12178444ba2f28c0ae558f.tar.gz gcc-1959aeee1e0e0b5eca12178444ba2f28c0ae558f.tar.bz2 | |
bpf: emit empty epilogues in naked functions
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.
| -rw-r--r-- | gcc/config/bpf/bpf.cc | 5 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.target/bpf/naked-1.c | 1 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.target/bpf/naked-2.c | 10 |
3 files changed, 12 insertions, 4 deletions
diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc index 9af1728..d6ca47e 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 cbbc4c5..dc8ac26 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 0000000..25aebf8 --- /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 } } */ |