From: Peter Zijlstra <peterz@infradead.org>
Date: Fri, 3 Dec 2021 10:44:10 +0100

On Thu, Dec 02, 2021 at 11:32:05PM +0100, Alexander Lobakin wrote:

quoted

Use the newly introduces macros to create unique separate sections
for (almost) every "regular" ASM function (i.e. for those which
aren't explicitly put into a specific one).
There should be no leftovers as input .text will be size-asserted
in the LD script generated for FG-KASLR.

*groan*...

Please, can't we do something like:

#define SYM_PUSH_SECTION(name)	\
.if section == .text		\
.push_section .text.##name	\
.else				\
.push_section .text		\
.endif

This condition

.pushsection .text
.if section == .text
# do something
.endif
.popsection

doesn't really works. `do something` doesn't happen.
This works only when

.pushsection .text
.equ section, .text

but it's not really okayish I'd say to find all .{,push}section
occurences and replace them with a macro (which would also do .equ).

I don't really know how %S with --sectname-subst should help me as

.if %S == .text
# do something
.endif

doesn't work at all (syntax error) -- and it shouldn't, %S is
supposed to work only inside .{,push}section directives.

I could do unconditional

.pushsection %S.##name
                ^^^^^^ function name

but this would involve changing LDS scripts (and vmlinux.lds.h) to
let's say replace *(.noinstr.text) with *(.noinstr.text*).

So I hope there is a way to get current section name? If not, then
the last option is the least harmful I suppose.
At least not as harmful as current approach with alternative macros,
far from it lol.

#define SYM_POP_SECTION()	\
.pop_section

and wrap that inside the existing SYM_FUNC_START*() SYM_FUNC_END()
macros.

Thanks,
Al