This is a note to let you know that I've just added the patch titled
ARM: net: bpf: correct stack layout documentation
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-net-bpf-correct-stack-layout-documentation.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0005e55a79cfda88199e41a406a829c88d708c67 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Date: Sat, 13 Jan 2018 22:51:27 +0000
Subject: ARM: net: bpf: correct stack layout documentation
From: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
commit 0005e55a79cfda88199e41a406a829c88d708c67 upstream.
The stack layout documentation incorrectly suggests that the BPF JIT
scratch space starts immediately below BPF_FP. This is not correct,
so let's fix the documentation to reflect reality.
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/net/bpf_jit_32.c | 35 +++++++++++++++++++++++++++--------
1 file changed, 27 insertions(+), 8 deletions(-)
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -28,24 +28,43 @@
int bpf_jit_enable __read_mostly;
/*
- * eBPF prog stack layout
+ * eBPF prog stack layout:
*
* high
- * original ARM_SP => +-----+ eBPF prologue
- * |FP/LR|
- * current ARM_FP => +-----+
- * | ... | callee saved registers
- * eBPF fp register => +-----+ <= (BPF_FP)
+ * original ARM_SP => +-----+
+ * | | callee saved registers
+ * +-----+ <= (BPF_FP + SCRATCH_SIZE)
* | ... | eBPF JIT scratch space
- * | | eBPF prog stack
+ * eBPF fp register => +-----+
+ * (BPF_FP) | ... | eBPF prog stack
* +-----+
* |RSVD | JIT scratchpad
- * current ARM_SP => +-----+ <= (BPF_FP - STACK_SIZE)
+ * current ARM_SP => +-----+ <= (BPF_FP - STACK_SIZE + SCRATCH_SIZE)
* | |
* | ... | Function call stack
* | |
* +-----+
* low
+ *
+ * The callee saved registers depends on whether frame pointers are enabled.
+ * With frame pointers (to be compliant with the ABI):
+ *
+ * high
+ * original ARM_SP => +------------------+ \
+ * | pc | |
+ * current ARM_FP => +------------------+ } callee saved registers
+ * |r4-r8,r10,fp,ip,lr| |
+ * +------------------+ /
+ * low
+ *
+ * Without frame pointers:
+ *
+ * high
+ * original ARM_SP => +------------------+
+ * | lr | (optional)
+ * | r4-r8,r10 | callee saved registers
+ * +------------------+
+ * low
*/
#define STACK_OFFSET(k) (k)
Patches currently in stable-queue which might be from rmk+kernel@xxxxxxxxxxxxxxx are
queue-4.14/arm-net-bpf-fix-stack-alignment.patch
queue-4.14/arm-net-bpf-fix-ldx-instructions.patch
queue-4.14/arm-net-bpf-fix-register-saving.patch
queue-4.14/arm-net-bpf-move-stack-documentation.patch
queue-4.14/arm-net-bpf-correct-stack-layout-documentation.patch
queue-4.14/arm-net-bpf-clarify-tail_call-index.patch
queue-4.14/arm-net-bpf-avoid-bx-instruction-on-non-thumb-capable-cpus.patch
queue-4.14/arm-net-bpf-fix-tail-call-jumps.patch