Clarify definitions of several instructions:
* BPF_NEG does not support BPF_X
* BPF_CALL does not support BPF_JMP32 or BPF_X
* BPF_EXIT does not support BPF_X
* BPF_JA does not support BPF_X (was implied but not explicitly stated)
Also fix a typo in the wide instruction figure where
the field is actually named "opcode" not "code".
Signed-off-by: Dave Thaler <dthaler1968@xxxxxxxxx>
---
.../bpf/standardization/instruction-set.rst | 51 ++++++++++---------
1 file changed, 27 insertions(+), 24 deletions(-)
diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
index d17a96c62..af43227b6 100644
--- a/Documentation/bpf/standardization/instruction-set.rst
+++ b/Documentation/bpf/standardization/instruction-set.rst
@@ -174,12 +174,12 @@ and imm containing the high 32 bits of the immediate value.
This is depicted in the following figure::
basic_instruction
- .-----------------------------.
- | |
- code:8 regs:8 offset:16 imm:32 unused:32 imm:32
- | |
- '--------------'
- pseudo instruction
+ .------------------------------.
+ | |
+ opcode:8 regs:8 offset:16 imm:32 unused:32 imm:32
+ | |
+ '--------------'
+ pseudo instruction
Thus the 64-bit immediate value is constructed as follows:
@@ -320,6 +320,9 @@ bit operands, and zeroes the remaining upper 32 bits.
operands into 64 bit operands. Unlike other arithmetic instructions,
``BPF_MOVSX`` is only defined for register source operands (``BPF_X``).
+The ``BPF_NEG`` instruction is only defined when the source bit is clear
+(``BPF_K``).
+
Shift operations use a mask of 0x3F (63) for 64-bit operations and 0x1F (31)
for 32-bit operations.
@@ -375,27 +378,27 @@ Jump instructions
otherwise identical operations.
The 'code' field encodes the operation as below:
-======== ===== === =========================================== =========================================
-code value src description notes
-======== ===== === =========================================== =========================================
-BPF_JA 0x0 0x0 PC += offset BPF_JMP class
-BPF_JA 0x0 0x0 PC += imm BPF_JMP32 class
+======== ===== === =============================== =============================================
+code value src description notes
+======== ===== === =============================== =============================================
+BPF_JA 0x0 0x0 PC += offset BPF_JMP | BPF_K only
+BPF_JA 0x0 0x0 PC += imm BPF_JMP32 | BPF_K 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_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 by address see `Helper functions`_
-BPF_CALL 0x8 0x1 call PC += imm see `Program-local functions`_
-BPF_CALL 0x8 0x2 call helper function by BTF ID see `Helper 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
-======== ===== === =========================================== =========================================
+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 by address BPF_JMP | BPF_K only, see `Helper functions`_
+BPF_CALL 0x8 0x1 call PC += imm BPF_JMP | BPF_K only, see `Program-local functions`_
+BPF_CALL 0x8 0x2 call helper function by BTF ID BPF_JMP | BPF_K only, see `Helper functions`_
+BPF_EXIT 0x9 0x0 return BPF_JMP | BPF_K 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
+======== ===== === =============================== =============================================
The BPF program needs to store the return value into register R0 before doing a
``BPF_EXIT``.
--
2.40.1
