[loader] fix file name cut causing hang when a "." is found in paths like "boot/kernel.elfv2/kernel"

[alfredo]

Summary

function fake_modname is prepared to read a full path to a file and retrieve its name, without and extension (".").
As example, in a path like "boot/kernel.elfv2", the substring "kernel" is extracted.

However, in paths like "boot/test.elfv2/kernel", the dot (".") is being misidentified, causes incorrect string length being calculated. It should look for a "dot" only in the last part of the file name, after the last slash character.

Note: the kernel used in this test doesn't contain any valid module, so it falls in " if (modcnt == 0)" in "__elfN(parse_modmetadata)" functions, causing fake_modname being called.

Test Plan

fix verified in QEMU VM (slof loader)

[emaste]

stand/common/load_elf.c

873 ↗

(On Diff #55283)

should this be ep == sp now? I'm not sure what exactly the intent of this check is though.

[kevans]

stand/common/load_elf.c

873 ↗

(On Diff #55283)

Right, this is supposed to be weeding out boot/kernel.elfv2/.elf type stuff where there's no 'name' component. name is the beginning of string, still, and wrong in any case where there's a path separator.

878 ↗

(On Diff #55283)

This could be changed to s/name/sp/, but it's effectively the same - perhaps just as little more consistent with the other branch.

[alfredo]

addresses comments from reviewers and also translates paths such as "boot/kernel/", /boot/kernel/.", ".", "/.", "/.elf", ".elf" as: "bad" (invalid_name variable)