Christophe Leroy wrote:
Le 06/01/2022 à 12:45, Naveen N. Rao a écrit :
In preparation for using kernel TOC, load the same in r2 on entry. With
elfv1, the kernel TOC is already setup by our caller so we just emit a
nop. We adjust the number of instructions to skip on a tail call
accordingly.
Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/net/bpf_jit_comp64.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index ce4fc59bbd6a92..e05b577d95bf11 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -73,6 +73,12 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
{
int i;
+#ifdef PPC64_ELF_ABI_v2
+ PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc));
+#else
+ EMIT(PPC_RAW_NOP());
+#endif
Can we avoid the #ifdef, using
if (__is_defined(PPC64_ELF_ABI_v2))
PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc));
else
EMIT(PPC_RAW_NOP());
Hmm... that doesn't work for me. Is __is_defined() expected to work with
macros other than CONFIG options?
+
/*
* Initialize tail_call_cnt if we do tail calls.
* Otherwise, put in NOPs so that it can be skipped when we are
@@ -87,7 +93,7 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)
EMIT(PPC_RAW_NOP());
}
-#define BPF_TAILCALL_PROLOGUE_SIZE 8
+#define BPF_TAILCALL_PROLOGUE_SIZE 12
Why not change that for v2 ABI only instead of adding a NOP ? ABI won't
change during runtime AFAIU
Yeah, I wanted to keep this simple and I felt an additional nop
shouldn't matter too much. But, I guess we can get rid of
BPF_TAILCALL_PROLOGUE_SIZE since the only user is the function emitting
a tail call. I will submit that as a separate cleanup unless I need to
redo this series.
Thanks for the reviews!
- Naveen
