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Date: Fri, 30 Jul 2021 22:19:20 +0000
From: "Williams, Dan J" <dan.j.williams@...el.com>
To: "keescook@...omium.org" <keescook@...omium.org>,
"linux@...musvillemoes.dk" <linux@...musvillemoes.dk>
CC: "keithpac@...zon.com" <keithpac@...zon.com>,
"clang-built-linux@...glegroups.com"
<clang-built-linux@...glegroups.com>,
"linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
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"linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: [PATCH 04/64] stddef: Introduce struct_group() helper macro
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
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