[PATCH 14/15] ebpf-docs: Add extended call instructions

[dthaler1968@googlemail.com]

From: Dave Thaler <dthaler@microsoft.com>

Signed-off-by: Dave Thaler <dthaler@microsoft.com>
---
 Documentation/bpf/instruction-set.rst | 52 +++++++++++++++++----------
 1 file changed, 34 insertions(+), 18 deletions(-)

diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
index 667d97715..2ac8f0dae 100644
--- a/Documentation/bpf/instruction-set.rst
+++ b/Documentation/bpf/instruction-set.rst
@@ -265,24 +265,26 @@ otherwise identical operations.
 
 The 4-bit 'code' field encodes the operation as below, where PC is the program counter:
 
-========  =====  =========================  ============
-code      value  description                notes
-========  =====  =========================  ============
-BPF_JA    0x00   PC += off                  BPF_JMP only
-BPF_JEQ   0x10   PC += off if dst == src
-BPF_JGT   0x20   PC += off if dst > src     unsigned
-BPF_JGE   0x30   PC += off if dst >= src    unsigned
-BPF_JSET  0x40   PC += off if dst & src
-BPF_JNE   0x50   PC += off if dst != src
-BPF_JSGT  0x60   PC += off if dst > src     signed
-BPF_JSGE  0x70   PC += off if dst >= src    signed
-BPF_CALL  0x80   function call              see `Helper functions`_
-BPF_EXIT  0x90   function / program return  BPF_JMP only
-BPF_JLT   0xa0   PC += off if dst < src     unsigned
-BPF_JLE   0xb0   PC += off if dst <= src    unsigned
-BPF_JSLT  0xc0   PC += off if dst < src     signed
-BPF_JSLE  0xd0   PC += off if dst <= src    signed
-========  =====  =========================  ============
+========  =====  ===  ==========================  ========================
+code      value  src  description                 notes
+========  =====  ===  ==========================  ========================
+BPF_JA    0x0    0x0  PC += offset                BPF_JMP only
+BPF_JEQ   0x1    any  PC += offset if dst == src
+BPF_JGT   0x2    any  PC += offset if dst > src   unsigned
+BPF_JGE   0x3    any  PC += offset if dst >= src  unsigned
+BPF_JSET  0x4    any  PC += offset if dst & src
+BPF_JNE   0x5    any  PC += offset if dst != src
+BPF_JSGT  0x6    any  PC += offset if dst > src   signed
+BPF_JSGE  0x7    any  PC += offset if dst >= src  signed
+BPF_CALL  0x8    0x0  call helper function imm    see `Helper functions`_
+BPF_CALL  0x8    0x1  call PC += offset           see `eBPF functions`_
+BPF_CALL  0x8    0x2  call runtime function imm   see `Runtime functions`_
+BPF_EXIT  0x9    0x0  return                      BPF_JMP only
+BPF_JLT   0xa    any  PC += offset if dst < src   unsigned
+BPF_JLE   0xb    any  PC += offset if dst <= src  unsigned
+BPF_JSLT  0xc    any  PC += offset if dst < src   signed
+BPF_JSLE  0xd    any  PC += offset if dst <= src  signed
+========  =====  ===  ==========================  ========================
 
 Helper functions
 ~~~~~~~~~~~~~~~~
@@ -301,6 +303,18 @@ with the remaining registers being ignored.  The definition of a helper function
 is responsible for specifying the type (e.g., integer, pointer, etc.) of the value returned,
 the number of arguments, and the type of each argument.
 
+Runtime functions
+~~~~~~~~~~~~~~~~~
+Runtime functions are like helper functions except that they are not specific
+to eBPF programs.  They use a different numbering space from helper functions,
+but otherwise the same considerations apply.
+
+eBPF functions
+~~~~~~~~~~~~~~
+eBPF functions are functions exposed by the same eBPF program as the caller,
+and are referenced by offset from the call instruction, similar to ``BPF_JA``.
+A ``BPF_EXIT`` within the eBPF function will return to the caller.
+
 Load and store instructions
 ===========================
 
@@ -585,6 +599,8 @@ opcode  src  imm   description                                          referenc
 0x7f    any  0x00  dst >>= src                                          `Arithmetic instructions`_
 0x84    0x0  0x00  dst = (uint32_t)-dst                                 `Arithmetic instructions`_
 0x85    0x0  any   call helper function imm                             `Helper functions`_
+0x85    0x1  any   call PC += offset                                    `eBPF functions`_
+0x85    0x2  any   call runtime function imm                            `Runtime functions`_
 0x87    0x0  0x00  dst = -dst                                           `Arithmetic instructions`_
 0x94    0x0  any   dst = (uint32_t)((imm != 0) ? (dst % imm) : dst)     `Arithmetic instructions`_
 0x95    0x0  0x00  return                                               `Jump instructions`_
-- 
2.33.4