Patch "ARM: net: bpf: correct stack layout documentation" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

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@vger.kernel.org> know about it.


>From 0005e55a79cfda88199e41a406a829c88d708c67 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Sat, 13 Jan 2018 22:51:27 +0000
Subject: ARM: net: bpf: correct stack layout documentation

From: Russell King <rmk+kernel@armlinux.org.uk>

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@armlinux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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@armlinux.org.uk 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