On Mon, Mar 13, 2023 at 10:48:53PM +0100, Michal Suchánek wrote:

Hello,

On Mon, Mar 13, 2023 at 09:32:16PM +0100, Andrea Righi wrote:

quoted

On Wed, Jan 11, 2023 at 04:11:51PM +0000, Gary Guo wrote:

quoted

Currently modversion uses a fixed size array of size (64 - sizeof(long))
to store symbol names, thus placing a hard limit on length of symbols.
Rust symbols (which encodes crate and module names) can be quite a bit
longer. The length limit in kallsyms is increased to 512 for this reason.

It's a waste of space to simply expand the fixed array size to 512 in
modversion info entries. I therefore make it variably sized, with offset
to the next entry indicated by the initial "next" field.

In addition to supporting longer-than-56/60 byte symbols, this patch also
reduce the size for short symbols by getting rid of excessive 0 paddings.
There are still some zero paddings to ensure "next" and "crc" fields are
properly aligned.

This patch does have a tiny drawback that it makes ".mod.c" files generated
a bit less easy to read, as code like

	"\x08\x00\x00\x00\x78\x56\x34\x12"
	"symbol\0\0"

is generated as opposed to

	{ 0x12345678, "symbol" },

because the structure is now variable-length. But hopefully nobody reads
the generated file :)

Link: b8a94bfb3395 ("kallsyms: increase maximum kernel symbol length to 512")
Link: https://github.com/Rust-for-Linux/linux/pull/379

Signed-off-by: Gary Guo <gary@garyguo.net>

Is there any newer version of this patch?

I'm doing some tests with it, but I'm getting boot failures on ppc64
with this applied (at boot kernel is spitting out lots of oops'es and
unfortunately it's really hard to copy paste or just read them from the
console).

Are you using the ELF ABI v1 or v2?

v1 may have some additional issues when it comes to these symbol tables.

Thanks

Michal

I have CONFIG_PPC64_ELF_ABI_V2=y in my .config, so I guess I'm using v2.

BTW, the issue seems to be in dedotify_versions(), as a silly test I
tried to comment out this function completely to be a no-op and now my
system boots fine (but I guess I'm probably breaking something else).

Thanks,
-Andrea