* Re: [PATCH 04/64] stddef: Introduce struct_group() helper macro
[not found] ` <202107281456.1A3A5C18@keescook>
@ 2021-07-30 22:19 ` Williams, Dan J
2021-07-31 2:59 ` Kees Cook
0 siblings, 1 reply; 3+ messages in thread
From: Williams, Dan J @ 2021-07-30 22:19 UTC (permalink / raw)
To: keescook, linux
Cc: keithpac, clang-built-linux, linux-kbuild, akpm, gregkh,
dri-devel, linux-cxl, linux-kernel, linux-wireless, netdev,
linux-hardening, gustavoars, linux-staging, linux-block
On Wed, 2021-07-28 at 14:59 -0700, Kees Cook wrote:
> On Wed, Jul 28, 2021 at 12:54:18PM +0200, Rasmus Villemoes wrote:
> > On 27/07/2021 22.57, Kees Cook wrote:
> >
> > > In order to have a regular programmatic way to describe a struct
> > > region that can be used for references and sizing, can be examined for
> > > bounds checking, avoids forcing the use of intermediate identifiers,
> > > and avoids polluting the global namespace, introduce the struct_group()
> > > macro. This macro wraps the member declarations to create an anonymous
> > > union of an anonymous struct (no intermediate name) and a named struct
> > > (for references and sizing):
> > >
> > > struct foo {
> > > int one;
> > > struct_group(thing,
> > > int two,
> > > int three,
> > > );
> > > int four;
> > > };
> >
> > That example won't compile, the commas after two and three should be
> > semicolons.
>
> Oops, yes, thanks. This is why I shouldn't write code that doesn't first
> go through a compiler. ;)
>
> > And your implementation relies on MEMBERS not containing any comma
> > tokens, but as
> >
> > int a, b, c, d;
> >
> > is a valid way to declare multiple members, consider making MEMBERS
> > variadic
> >
> > #define struct_group(NAME, MEMBERS...)
> >
> > to have it slurp up every subsequent argument and make that work.
>
> Ah! Perfect, thank you. I totally forgot I could do it that way.
This is great Kees. It just so happens it would clean-up what we are
already doing in drivers/cxl/cxl.h for anonymous + named register block
pointers. However in the cxl case it also needs the named structure to
be typed. Any appetite for a typed version of this?
Here is a rough idea of the cleanup it would induce in drivers/cxl/:
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 53927f9fa77e..a2308c995654 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -75,52 +75,19 @@ static inline int cxl_hdm_decoder_count(u32 cap_hdr)
#define CXLDEV_MBOX_BG_CMD_STATUS_OFFSET 0x18
#define CXLDEV_MBOX_PAYLOAD_OFFSET 0x20
-#define CXL_COMPONENT_REGS() \
- void __iomem *hdm_decoder
-
-#define CXL_DEVICE_REGS() \
- void __iomem *status; \
- void __iomem *mbox; \
- void __iomem *memdev
-
-/* See note for 'struct cxl_regs' for the rationale of this organization */
/*
- * CXL_COMPONENT_REGS - Common set of CXL Component register block base pointers
* @hdm_decoder: CXL 2.0 8.2.5.12 CXL HDM Decoder Capability Structure
- */
-struct cxl_component_regs {
- CXL_COMPONENT_REGS();
-};
-
-/* See note for 'struct cxl_regs' for the rationale of this organization */
-/*
- * CXL_DEVICE_REGS - Common set of CXL Device register block base pointers
* @status: CXL 2.0 8.2.8.3 Device Status Registers
* @mbox: CXL 2.0 8.2.8.4 Mailbox Registers
* @memdev: CXL 2.0 8.2.8.5 Memory Device Registers
*/
-struct cxl_device_regs {
- CXL_DEVICE_REGS();
-};
-
-/*
- * Note, the anonymous union organization allows for per
- * register-block-type helper routines, without requiring block-type
- * agnostic code to include the prefix.
- */
struct cxl_regs {
- union {
- struct {
- CXL_COMPONENT_REGS();
- };
- struct cxl_component_regs component;
- };
- union {
- struct {
- CXL_DEVICE_REGS();
- };
- struct cxl_device_regs device_regs;
- };
+ struct_group_typed(cxl_component_regs, component,
+ void __iomem *hdm_decoder;
+ );
+ struct_group_typed(cxl_device_regs, device_regs,
+ void __iomem *status, *mbox, *memdev;
+ );
};
struct cxl_reg_map {
diff --git a/include/linux/stddef.h b/include/linux/stddef.h
index cf7f866944f9..84b7de24ffb5 100644
--- a/include/linux/stddef.h
+++ b/include/linux/stddef.h
@@ -49,12 +49,18 @@ enum {
* @ATTRS: Any struct attributes (normally empty)
* @MEMBERS: The member declarations for the mirrored structs
*/
-#define struct_group_attr(NAME, ATTRS, MEMBERS) \
+#define struct_group_attr(NAME, ATTRS, MEMBERS...) \
union { \
struct { MEMBERS } ATTRS; \
struct { MEMBERS } ATTRS NAME; \
}
+#define struct_group_attr_typed(TYPE, NAME, ATTRS, MEMBERS...) \
+ union { \
+ struct { MEMBERS } ATTRS; \
+ struct TYPE { MEMBERS } ATTRS NAME; \
+ }
+
/**
* struct_group(NAME, MEMBERS)
*
@@ -67,7 +73,10 @@ enum {
* @NAME: The name of the mirrored sub-struct
* @MEMBERS: The member declarations for the mirrored structs
*/
-#define struct_group(NAME, MEMBERS) \
+#define struct_group(NAME, MEMBERS...) \
struct_group_attr(NAME, /* no attrs */, MEMBERS)
+#define struct_group_typed(TYPE, NAME, MEMBERS...) \
+ struct_group_attr_typed(TYPE, NAME, /* no attrs */, MEMBERS)
+
#endif
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH 04/64] stddef: Introduce struct_group() helper macro
2021-07-30 22:19 ` [PATCH 04/64] stddef: Introduce struct_group() helper macro Williams, Dan J
@ 2021-07-31 2:59 ` Kees Cook
[not found] ` <CAKwiHFheDv2pwsm6Fa+-KnOFyvk7bfZQjb2BQ-CSwH61gxgVYg@mail.gmail.com>
0 siblings, 1 reply; 3+ messages in thread
From: Kees Cook @ 2021-07-31 2:59 UTC (permalink / raw)
To: Williams, Dan J
Cc: linux, keithpac, clang-built-linux, linux-kbuild, akpm, gregkh,
dri-devel, linux-cxl, linux-kernel, linux-wireless, netdev,
linux-hardening, gustavoars, linux-staging, linux-block
On Fri, Jul 30, 2021 at 10:19:20PM +0000, Williams, Dan J wrote:
> On Wed, 2021-07-28 at 14:59 -0700, Kees Cook wrote:
> > On Wed, Jul 28, 2021 at 12:54:18PM +0200, Rasmus Villemoes wrote:
> > > On 27/07/2021 22.57, Kees Cook wrote:
> > >
> > > > In order to have a regular programmatic way to describe a struct
> > > > region that can be used for references and sizing, can be examined for
> > > > bounds checking, avoids forcing the use of intermediate identifiers,
> > > > and avoids polluting the global namespace, introduce the struct_group()
> > > > macro. This macro wraps the member declarations to create an anonymous
> > > > union of an anonymous struct (no intermediate name) and a named struct
> > > > (for references and sizing):
> > > >
> > > > struct foo {
> > > > int one;
> > > > struct_group(thing,
> > > > int two,
> > > > int three,
> > > > );
> > > > int four;
> > > > };
> > >
> > > That example won't compile, the commas after two and three should be
> > > semicolons.
> >
> > Oops, yes, thanks. This is why I shouldn't write code that doesn't first
> > go through a compiler. ;)
> >
> > > And your implementation relies on MEMBERS not containing any comma
> > > tokens, but as
> > >
> > > int a, b, c, d;
> > >
> > > is a valid way to declare multiple members, consider making MEMBERS
> > > variadic
> > >
> > > #define struct_group(NAME, MEMBERS...)
> > >
> > > to have it slurp up every subsequent argument and make that work.
> >
> > Ah! Perfect, thank you. I totally forgot I could do it that way.
>
> This is great Kees. It just so happens it would clean-up what we are
> already doing in drivers/cxl/cxl.h for anonymous + named register block
> pointers. However in the cxl case it also needs the named structure to
> be typed. Any appetite for a typed version of this?
Oh cool! Yeah, totally I can expand it. Thanks for the suggestion!
>
> Here is a rough idea of the cleanup it would induce in drivers/cxl/:
>
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 53927f9fa77e..a2308c995654 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -75,52 +75,19 @@ static inline int cxl_hdm_decoder_count(u32 cap_hdr)
> #define CXLDEV_MBOX_BG_CMD_STATUS_OFFSET 0x18
> #define CXLDEV_MBOX_PAYLOAD_OFFSET 0x20
>
> -#define CXL_COMPONENT_REGS() \
> - void __iomem *hdm_decoder
> -
> -#define CXL_DEVICE_REGS() \
> - void __iomem *status; \
> - void __iomem *mbox; \
> - void __iomem *memdev
> -
> -/* See note for 'struct cxl_regs' for the rationale of this organization */
> /*
> - * CXL_COMPONENT_REGS - Common set of CXL Component register block base pointers
> * @hdm_decoder: CXL 2.0 8.2.5.12 CXL HDM Decoder Capability Structure
> - */
> -struct cxl_component_regs {
> - CXL_COMPONENT_REGS();
> -};
> -
> -/* See note for 'struct cxl_regs' for the rationale of this organization */
> -/*
> - * CXL_DEVICE_REGS - Common set of CXL Device register block base pointers
> * @status: CXL 2.0 8.2.8.3 Device Status Registers
> * @mbox: CXL 2.0 8.2.8.4 Mailbox Registers
> * @memdev: CXL 2.0 8.2.8.5 Memory Device Registers
> */
> -struct cxl_device_regs {
> - CXL_DEVICE_REGS();
> -};
> -
> -/*
> - * Note, the anonymous union organization allows for per
> - * register-block-type helper routines, without requiring block-type
> - * agnostic code to include the prefix.
> - */
> struct cxl_regs {
> - union {
> - struct {
> - CXL_COMPONENT_REGS();
> - };
> - struct cxl_component_regs component;
> - };
> - union {
> - struct {
> - CXL_DEVICE_REGS();
> - };
> - struct cxl_device_regs device_regs;
> - };
> + struct_group_typed(cxl_component_regs, component,
> + void __iomem *hdm_decoder;
> + );
> + struct_group_typed(cxl_device_regs, device_regs,
> + void __iomem *status, *mbox, *memdev;
> + );
> };
>
> struct cxl_reg_map {
> diff --git a/include/linux/stddef.h b/include/linux/stddef.h
> index cf7f866944f9..84b7de24ffb5 100644
> --- a/include/linux/stddef.h
> +++ b/include/linux/stddef.h
> @@ -49,12 +49,18 @@ enum {
> * @ATTRS: Any struct attributes (normally empty)
> * @MEMBERS: The member declarations for the mirrored structs
> */
> -#define struct_group_attr(NAME, ATTRS, MEMBERS) \
> +#define struct_group_attr(NAME, ATTRS, MEMBERS...) \
> union { \
> struct { MEMBERS } ATTRS; \
> struct { MEMBERS } ATTRS NAME; \
> }
>
> +#define struct_group_attr_typed(TYPE, NAME, ATTRS, MEMBERS...) \
> + union { \
> + struct { MEMBERS } ATTRS; \
> + struct TYPE { MEMBERS } ATTRS NAME; \
> + }
> +
> /**
> * struct_group(NAME, MEMBERS)
> *
> @@ -67,7 +73,10 @@ enum {
> * @NAME: The name of the mirrored sub-struct
> * @MEMBERS: The member declarations for the mirrored structs
> */
> -#define struct_group(NAME, MEMBERS) \
> +#define struct_group(NAME, MEMBERS...) \
> struct_group_attr(NAME, /* no attrs */, MEMBERS)
>
> +#define struct_group_typed(TYPE, NAME, MEMBERS...) \
> + struct_group_attr_typed(TYPE, NAME, /* no attrs */, MEMBERS)
> +
> #endif
Awesome! My instinct is to expose the resulting API as:
__struct_group(type, name, attrs, members...)
struct_group(name, members...)
struct_group_attr(name, attrs, members...)
struct_group_typed(type, name, members...)
--
Kees Cook
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 04/64] stddef: Introduce struct_group() helper macro
[not found] ` <CAKwiHFheDv2pwsm6Fa+-KnOFyvk7bfZQjb2BQ-CSwH61gxgVYg@mail.gmail.com>
@ 2021-07-31 15:10 ` Kees Cook
0 siblings, 0 replies; 3+ messages in thread
From: Kees Cook @ 2021-07-31 15:10 UTC (permalink / raw)
To: Rasmus Villemoes
Cc: Williams, Dan J, keithpac, clang-built-linux, linux-kbuild, akpm,
gregkh, dri-devel, linux-cxl, linux-kernel, linux-wireless,
netdev, linux-hardening, gustavoars, linux-staging, linux-block
On Sat, Jul 31, 2021 at 07:24:44AM +0200, Rasmus Villemoes wrote:
> On Sat, Jul 31, 2021, 04:59 Kees Cook <keescook@chromium.org> wrote:
>
> > On Fri, Jul 30, 2021 at 10:19:20PM +0000, Williams, Dan J wrote:
> > > On Wed, 2021-07-28 at 14:59 -0700, Kees Cook wrote:
> >
> > > /**
> > > * struct_group(NAME, MEMBERS)
> > > *
> > > @@ -67,7 +73,10 @@ enum {
> > > * @NAME: The name of the mirrored sub-struct
> > > * @MEMBERS: The member declarations for the mirrored structs
> > > */
> > > -#define struct_group(NAME, MEMBERS) \
> > > +#define struct_group(NAME, MEMBERS...) \
> > > struct_group_attr(NAME, /* no attrs */, MEMBERS)
> > >
> > > +#define struct_group_typed(TYPE, NAME, MEMBERS...) \
> > > + struct_group_attr_typed(TYPE, NAME, /* no attrs */, MEMBERS)
> > > +
> > > #endif
> >
> > Awesome! My instinct is to expose the resulting API as:
> >
> > __struct_group(type, name, attrs, members...)
> >
> > struct_group(name, members...)
> > struct_group_attr(name, attrs, members...)
> > struct_group_typed(type, name, members...)
>
> Bikeshed: can we use proper nomenclature please. s/type/tag/,
> s/typed/tagged.
Ah! Thank you. I went looking for the spec on what these are called and
couldn't find it. "struct $tag" is the type, then, yes? So IIUC now:
| type | members | name
| tag
struct foo { int bar; } baz;
--
Kees Cook
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-07-30 22:19 ` [PATCH 04/64] stddef: Introduce struct_group() helper macro Williams, Dan J
2021-07-31 2:59 ` Kees Cook
[not found] ` <CAKwiHFheDv2pwsm6Fa+-KnOFyvk7bfZQjb2BQ-CSwH61gxgVYg@mail.gmail.com>
2021-07-31 15:10 ` Kees Cook
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