* [PATCH bpf-next v3] bpf, docs: Add callx instructions in new conformance group
@ 2024-02-13 17:51 Dave Thaler
2024-02-13 17:51 ` [Bpf] " Dave Thaler
2024-02-14 2:45 ` Alexei Starovoitov
0 siblings, 2 replies; 4+ messages in thread
From: Dave Thaler @ 2024-02-13 17:51 UTC (permalink / raw)
To: bpf; +Cc: bpf, Dave Thaler
* Add a "callx" conformance group
* Add callx rows to table
* Update helper function to section to be agnostic between BPF_K vs
BPF_X
* Rename "legacy" conformance group to "packet"
Based on mailing list discussion at
https://mailarchive.ietf.org/arch/msg/bpf/l5tNEgL-Wo7qSEuaGssOl5VChKk/
v1->v2: Incorporated feedback from Will Hawkins
v2->v3: Use "dst" not "imm" field
Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
---
.../bpf/standardization/instruction-set.rst | 31 ++++++++++++-------
1 file changed, 20 insertions(+), 11 deletions(-)
diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
index bdfe0cd0e..4bba656b6 100644
--- a/Documentation/bpf/standardization/instruction-set.rst
+++ b/Documentation/bpf/standardization/instruction-set.rst
@@ -127,7 +127,7 @@ This document defines the following conformance groups:
* divmul32: includes 32-bit division, multiplication, and modulo instructions.
* divmul64: includes divmul32, plus 64-bit division, multiplication,
and modulo instructions.
-* legacy: deprecated packet access instructions.
+* packet: deprecated packet access instructions.
Instruction encoding
====================
@@ -404,9 +404,12 @@ 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 BPF_JMP | BPF_K only, see `Helper functions`_
+BPF_CALL 0x8 0x0 call_by_address(imm) BPF_JMP | BPF_K only
+BPF_CALL 0x8 0x0 call_by_address(dst) BPF_JMP | BPF_X only
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_CALL 0x8 0x1 call PC += dst BPF_JMP | BPF_X only, see `Program-local functions`_
+BPF_CALL 0x8 0x2 call_by_btfid(imm) BPF_JMP | BPF_K only
+BPF_CALL 0x8 0x2 call_by_btfid(dst) BPF_JMP | BPF_X only
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
@@ -414,6 +417,11 @@ BPF_JSLT 0xc any PC += offset if dst < src signed
BPF_JSLE 0xd any PC += offset if dst <= src signed
======== ===== === =============================== =============================================
+where
+
+* call_by_address(value) means to call a helper function by the address specified by 'value' (see `Helper functions`_ for details)
+* call_by_btfid(value) means to call a helper function by the BTF ID specified by 'value' (see `Helper functions`_ for details)
+
The BPF program needs to store the return value into register R0 before doing a
``BPF_EXIT``.
@@ -438,8 +446,9 @@ specified by the 'imm' field. A > 16-bit conditional jump may be
converted to a < 16-bit conditional jump plus a 32-bit unconditional
jump.
-All ``BPF_CALL`` and ``BPF_JA`` instructions belong to the
-base32 conformance group.
+All ``BPF_CALL | BPF_X`` instructions belong to the callx
+conformance group. All other ``BPF_CALL`` instructions and all
+``BPF_JA`` instructions belong to the base32 conformance group.
Helper functions
~~~~~~~~~~~~~~~~
@@ -447,13 +456,13 @@ Helper functions
Helper functions are a concept whereby BPF programs can call into a
set of function calls exposed by the underlying platform.
-Historically, each helper function was identified by an address
-encoded in the imm field. The available helper functions may differ
-for each program type, but address values are unique across all program types.
+Historically, each helper function was identified by an address.
+The available helper functions may differ for each program type,
+but address values are unique across all program types.
Platforms that support the BPF Type Format (BTF) support identifying
-a helper function by a BTF ID encoded in the imm field, where the BTF ID
-identifies the helper name and type.
+a helper function by a BTF ID, where the BTF ID identifies the helper
+name and type.
Program-local functions
~~~~~~~~~~~~~~~~~~~~~~~
@@ -660,4 +669,4 @@ carried over from classic BPF. These instructions used an instruction
class of BPF_LD, a size modifier of BPF_W, BPF_H, or BPF_B, and a
mode modifier of BPF_ABS or BPF_IND. However, these instructions are
deprecated and should no longer be used. All legacy packet access
-instructions belong to the "legacy" conformance group.
+instructions belong to the "packet" conformance group.
--
2.40.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [Bpf] [PATCH bpf-next v3] bpf, docs: Add callx instructions in new conformance group
2024-02-13 17:51 [PATCH bpf-next v3] bpf, docs: Add callx instructions in new conformance group Dave Thaler
@ 2024-02-13 17:51 ` Dave Thaler
2024-02-14 2:45 ` Alexei Starovoitov
1 sibling, 0 replies; 4+ messages in thread
From: Dave Thaler @ 2024-02-13 17:51 UTC (permalink / raw)
To: bpf; +Cc: bpf, Dave Thaler
* Add a "callx" conformance group
* Add callx rows to table
* Update helper function to section to be agnostic between BPF_K vs
BPF_X
* Rename "legacy" conformance group to "packet"
Based on mailing list discussion at
https://mailarchive.ietf.org/arch/msg/bpf/l5tNEgL-Wo7qSEuaGssOl5VChKk/
v1->v2: Incorporated feedback from Will Hawkins
v2->v3: Use "dst" not "imm" field
Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
---
.../bpf/standardization/instruction-set.rst | 31 ++++++++++++-------
1 file changed, 20 insertions(+), 11 deletions(-)
diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
index bdfe0cd0e..4bba656b6 100644
--- a/Documentation/bpf/standardization/instruction-set.rst
+++ b/Documentation/bpf/standardization/instruction-set.rst
@@ -127,7 +127,7 @@ This document defines the following conformance groups:
* divmul32: includes 32-bit division, multiplication, and modulo instructions.
* divmul64: includes divmul32, plus 64-bit division, multiplication,
and modulo instructions.
-* legacy: deprecated packet access instructions.
+* packet: deprecated packet access instructions.
Instruction encoding
====================
@@ -404,9 +404,12 @@ 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 BPF_JMP | BPF_K only, see `Helper functions`_
+BPF_CALL 0x8 0x0 call_by_address(imm) BPF_JMP | BPF_K only
+BPF_CALL 0x8 0x0 call_by_address(dst) BPF_JMP | BPF_X only
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_CALL 0x8 0x1 call PC += dst BPF_JMP | BPF_X only, see `Program-local functions`_
+BPF_CALL 0x8 0x2 call_by_btfid(imm) BPF_JMP | BPF_K only
+BPF_CALL 0x8 0x2 call_by_btfid(dst) BPF_JMP | BPF_X only
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
@@ -414,6 +417,11 @@ BPF_JSLT 0xc any PC += offset if dst < src signed
BPF_JSLE 0xd any PC += offset if dst <= src signed
======== ===== === =============================== =============================================
+where
+
+* call_by_address(value) means to call a helper function by the address specified by 'value' (see `Helper functions`_ for details)
+* call_by_btfid(value) means to call a helper function by the BTF ID specified by 'value' (see `Helper functions`_ for details)
+
The BPF program needs to store the return value into register R0 before doing a
``BPF_EXIT``.
@@ -438,8 +446,9 @@ specified by the 'imm' field. A > 16-bit conditional jump may be
converted to a < 16-bit conditional jump plus a 32-bit unconditional
jump.
-All ``BPF_CALL`` and ``BPF_JA`` instructions belong to the
-base32 conformance group.
+All ``BPF_CALL | BPF_X`` instructions belong to the callx
+conformance group. All other ``BPF_CALL`` instructions and all
+``BPF_JA`` instructions belong to the base32 conformance group.
Helper functions
~~~~~~~~~~~~~~~~
@@ -447,13 +456,13 @@ Helper functions
Helper functions are a concept whereby BPF programs can call into a
set of function calls exposed by the underlying platform.
-Historically, each helper function was identified by an address
-encoded in the imm field. The available helper functions may differ
-for each program type, but address values are unique across all program types.
+Historically, each helper function was identified by an address.
+The available helper functions may differ for each program type,
+but address values are unique across all program types.
Platforms that support the BPF Type Format (BTF) support identifying
-a helper function by a BTF ID encoded in the imm field, where the BTF ID
-identifies the helper name and type.
+a helper function by a BTF ID, where the BTF ID identifies the helper
+name and type.
Program-local functions
~~~~~~~~~~~~~~~~~~~~~~~
@@ -660,4 +669,4 @@ carried over from classic BPF. These instructions used an instruction
class of BPF_LD, a size modifier of BPF_W, BPF_H, or BPF_B, and a
mode modifier of BPF_ABS or BPF_IND. However, these instructions are
deprecated and should no longer be used. All legacy packet access
-instructions belong to the "legacy" conformance group.
+instructions belong to the "packet" conformance group.
--
2.40.1
--
Bpf mailing list
Bpf@ietf.org
https://www.ietf.org/mailman/listinfo/bpf
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [Bpf] [PATCH bpf-next v3] bpf, docs: Add callx instructions in new conformance group
2024-02-13 17:51 [PATCH bpf-next v3] bpf, docs: Add callx instructions in new conformance group Dave Thaler
2024-02-13 17:51 ` [Bpf] " Dave Thaler
@ 2024-02-14 2:45 ` Alexei Starovoitov
2024-02-14 2:45 ` Alexei Starovoitov
1 sibling, 1 reply; 4+ messages in thread
From: Alexei Starovoitov @ 2024-02-14 2:45 UTC (permalink / raw)
To: Dave Thaler; +Cc: bpf, bpf, Dave Thaler
On Tue, Feb 13, 2024 at 9:51 AM Dave Thaler
<dthaler1968=40googlemail.com@dmarc.ietf.org> wrote:
>
> * Add a "callx" conformance group
> * Add callx rows to table
> * Update helper function to section to be agnostic between BPF_K vs
> BPF_X
> * Rename "legacy" conformance group to "packet"
>
> Based on mailing list discussion at
> https://mailarchive.ietf.org/arch/msg/bpf/l5tNEgL-Wo7qSEuaGssOl5VChKk/
>
> v1->v2: Incorporated feedback from Will Hawkins
>
> v2->v3: Use "dst" not "imm" field
>
> Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
> ---
> .../bpf/standardization/instruction-set.rst | 31 ++++++++++++-------
> 1 file changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
> index bdfe0cd0e..4bba656b6 100644
> --- a/Documentation/bpf/standardization/instruction-set.rst
> +++ b/Documentation/bpf/standardization/instruction-set.rst
> @@ -127,7 +127,7 @@ This document defines the following conformance groups:
> * divmul32: includes 32-bit division, multiplication, and modulo instructions.
> * divmul64: includes divmul32, plus 64-bit division, multiplication,
> and modulo instructions.
> -* legacy: deprecated packet access instructions.
> +* packet: deprecated packet access instructions.
>
> Instruction encoding
> ====================
> @@ -404,9 +404,12 @@ 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 BPF_JMP | BPF_K only, see `Helper functions`_
> +BPF_CALL 0x8 0x0 call_by_address(imm) BPF_JMP | BPF_K only
> +BPF_CALL 0x8 0x0 call_by_address(dst) BPF_JMP | BPF_X only
> 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_CALL 0x8 0x1 call PC += dst BPF_JMP | BPF_X only, see `Program-local functions`_
> +BPF_CALL 0x8 0x2 call_by_btfid(imm) BPF_JMP | BPF_K only
> +BPF_CALL 0x8 0x2 call_by_btfid(dst) BPF_JMP | BPF_X only
Sorry, but this takes it too far.
This is way too early to define exactly what callx will do.
Especially with all the flavors.
gcc/llvm generate callx when it's an indirect call.
PC += dst and other combinations don't match to what real CPU would do.
let's reserve callx BPF_CALL|BPF_X with any src_reg and imm as reserved
without defining what it does.
pw-bot: cr
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Bpf] [PATCH bpf-next v3] bpf, docs: Add callx instructions in new conformance group
2024-02-14 2:45 ` Alexei Starovoitov
@ 2024-02-14 2:45 ` Alexei Starovoitov
0 siblings, 0 replies; 4+ messages in thread
From: Alexei Starovoitov @ 2024-02-14 2:45 UTC (permalink / raw)
To: Dave Thaler; +Cc: bpf, bpf, Dave Thaler
On Tue, Feb 13, 2024 at 9:51 AM Dave Thaler
<dthaler1968=40googlemail.com@dmarc.ietf.org> wrote:
>
> * Add a "callx" conformance group
> * Add callx rows to table
> * Update helper function to section to be agnostic between BPF_K vs
> BPF_X
> * Rename "legacy" conformance group to "packet"
>
> Based on mailing list discussion at
> https://mailarchive.ietf.org/arch/msg/bpf/l5tNEgL-Wo7qSEuaGssOl5VChKk/
>
> v1->v2: Incorporated feedback from Will Hawkins
>
> v2->v3: Use "dst" not "imm" field
>
> Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
> ---
> .../bpf/standardization/instruction-set.rst | 31 ++++++++++++-------
> 1 file changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
> index bdfe0cd0e..4bba656b6 100644
> --- a/Documentation/bpf/standardization/instruction-set.rst
> +++ b/Documentation/bpf/standardization/instruction-set.rst
> @@ -127,7 +127,7 @@ This document defines the following conformance groups:
> * divmul32: includes 32-bit division, multiplication, and modulo instructions.
> * divmul64: includes divmul32, plus 64-bit division, multiplication,
> and modulo instructions.
> -* legacy: deprecated packet access instructions.
> +* packet: deprecated packet access instructions.
>
> Instruction encoding
> ====================
> @@ -404,9 +404,12 @@ 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 BPF_JMP | BPF_K only, see `Helper functions`_
> +BPF_CALL 0x8 0x0 call_by_address(imm) BPF_JMP | BPF_K only
> +BPF_CALL 0x8 0x0 call_by_address(dst) BPF_JMP | BPF_X only
> 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_CALL 0x8 0x1 call PC += dst BPF_JMP | BPF_X only, see `Program-local functions`_
> +BPF_CALL 0x8 0x2 call_by_btfid(imm) BPF_JMP | BPF_K only
> +BPF_CALL 0x8 0x2 call_by_btfid(dst) BPF_JMP | BPF_X only
Sorry, but this takes it too far.
This is way too early to define exactly what callx will do.
Especially with all the flavors.
gcc/llvm generate callx when it's an indirect call.
PC += dst and other combinations don't match to what real CPU would do.
let's reserve callx BPF_CALL|BPF_X with any src_reg and imm as reserved
without defining what it does.
pw-bot: cr
--
Bpf mailing list
Bpf@ietf.org
https://www.ietf.org/mailman/listinfo/bpf
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2024-02-13 17:51 [PATCH bpf-next v3] bpf, docs: Add callx instructions in new conformance group Dave Thaler
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2024-02-14 2:45 ` Alexei Starovoitov
2024-02-14 2:45 ` Alexei Starovoitov
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