Le 14/01/2026 à 12:44, [email protected] a écrit :
From: Abhishek Dubey <[email protected]>
In the conventional stack frame, the position of tail_call_cnt
is after the NVR save area (BPF_PPC_STACK_SAVE). Whereas, the
offset of tail_call_cnt in the trampoline frame is after the
stack alignment padding. BPF JIT logic could become complex
when dealing with frame-sensitive offset calculation of
tail_call_cnt. Having the same offset in both frames is the
desired objective.
The trampoline frame does not have a BPF_PPC_STACK_SAVE area.
Introducing it leads to under-utilization of extra memory meant
only for the offset alignment of tail_call_cnt.
Another challenge is the variable alignment padding sitting at
the bottom of the trampoline frame, which requires additional
handling to compute tail_call_cnt offset.
This patch addresses the above issues by moving tail_call_cnt
to the bottom of the stack frame at offset 0 for both types
of frames. This saves additional bytes required by BPF_PPC_STACK_SAVE
in trampoline frame, and a common offset computation for
tail_call_cnt serves both frames.
The changes in this patch are required by the third patch in the
series, where the 'reference to tail_call_info' of the main frame
is copied into the trampoline frame from the previous frame.
Signed-off-by: Abhishek Dubey <[email protected]>
---
arch/powerpc/net/bpf_jit.h | 4 ++++
arch/powerpc/net/bpf_jit_comp64.c | 31 ++++++++++++++++++++-----------
2 files changed, 24 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index 8334cd667bba..45d419c0ee73 100644
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -72,6 +72,10 @@
} } while (0)
#ifdef CONFIG_PPC64
+
+/* for tailcall counter */
+#define BPF_PPC_TAILCALL 8
This needs to be defined outside of CONFIG_PPC64 ifdef because from
patch 3 it is used in bpf_jit_comp.c which is also built on powerpc32.
+
/* If dummy pass (!image), account for maximum possible instructions */
#define PPC_LI64(d, i) do {
\
if (!image) \
