Prepare the system for _FORTIFY_SOURCE

[kevans]

Summary

Notably:

• libc needs to #undef some of the macros from ssp/* for underlying implementations
• ssp/* wants a __RENAME() macro (snatched more or less from NetBSD)

There's some extra hinkiness included for read(), since libc spells it
as "_read" while the rest of the world spells it "read."

[imp]

Re _read, I thought all system calls had three functions foo, _foo and sys_foo depending on which layer of indirection you were trying to bypass... I know that's why libc uses things like _read and _write.

[kevans]

In D32307#729071, @imp wrote:

Re _read, I thought all system calls had three functions foo, _foo and sys_foo depending on which layer of indirection you were trying to bypass... I know that's why libc uses things like _read and _write.

Right, sorry, I need to update that comment.

[imp]

In D32307#729072, @kevans wrote:

In D32307#729071, @imp wrote:

Re _read, I thought all system calls had three functions foo, _foo and sys_foo depending on which layer of indirection you were trying to bypass... I know that's why libc uses things like _read and _write.

Right, sorry, I need to update that comment.

You've likely already thought of this, but if not... do we need to _FORTIFY_SOURCE system calls that FreeBSD has that are 'read like' that aren't in NetBSD?

[arichardson]

lib/libc/amd64/string/bcopy.c

8

(bcopy) will prevent function macro expansion, no need for #undef. Same for the other files.

[kib]

lib/libc/Makefile

22

I am not sure about all current and future uses of this define, but I dislike it being taken from the user namespace.

Usually we use something like _IN_LIBC

[kevans]

lib/libc/Makefile

22

It also wouldn't be used much, but I wonder if it'd be better to just -D_FORTIFY_SOURCE_read=_read and default _FORTIFY_SOURCE_read to read in the header.

[kevans]

Just prevent macro expansion, and use -D_FORTIFY_SOURCE_read instead of defining
some indicator for "in libc" to be misused later.

[imp]

lib/libc/sys/read.c

39 ↗

(On Diff #96308)

you only changed an include...
and nothing else...
So what does this accomplish?

sys/sys/cdefs.h

615–616

I'm torn on this #else...
It means that no compilers that don't define PCC nor GNUC will be an automatic error
EVEN IF THEY DONT USE __RENAME()

So that's bad, right? I'd be tempted to either leave it undefined or # it like you do for kernel standalone....

[kevans]

• Remove include that was shadily added that doesn't seem to be needed now
• Don't break with __RENAME() use unless it's used

The latter means these compilers can still build against our headers as long as
they don't enable _FORTIFY_SOURCE.