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