[LU-9698] osd-ldiskfs: unknown symbol error on patched kernel

• Type: Bug
• Resolution: Won't Fix
• Priority: Minor
• Environment: Centos6 - patched kernel
• Severity: 3
• Assignee: Oleg Drokin
• Reporter: CEA

Description

Running llmount.sh from master with a patched kernel fails with:

$> llmount.sh
[...]
insmod: error inserting '/home/user/lustre-release/lustre/tests/../osd-ldiskfs/osd_ldiskfs.ko': -1 Unknown symbol in module

Output of dmesg:

$> dmesg | tail -1
osd_diskfs Unknown symbol kallsyms_lookup_name (err 0)

The problem appears after commit 0f0a43b

Issue Links

• is related to: LU-20 patchless server kernel

Comments

[Peter Jones]

I agree James

[James A Simmons]

Now that https://review.whamcloud.com/28029 which Bob had RHEL6.9 kernel include a patch to export kallsyms when build RHEL kernel. This is fine since RHEL6 kernels will never be patchless like RHEL7 kernels. We should be able to close this since this is the case?

[Andreas Dilger]

It looks like RHEL6 has EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol) that could be used for doing the symbol lookup, like:

#ifndef HAVE_KALLSYMS_LOOKUP_NAME
int kallsyms_strcmp(void *name, const char *symbol_name, struct module *, unsigned long symbol_address)
{
        return strcmp(name, symbol_name) == 0 ? symbol_address : 0;
}

/* Note that kallsyms_strcmp() cannot return the full symbol address, only the low 32 bits.
 * We can handle this by extracting the high word from some other kernel function */
unsigned long ll_kallsyms_lookup_name(const char *name)
{
        unsigned int low_addr = kallsyms_on_each_symbol(kallsyms_strcmp, name);

        return low_addr ? kallsyms_on_each_symbol & 0xffffffff00000000ULL | low_addr : 0;
}
#else
#define ll_kallsyms_lookup_name(name) kallsyms_lookup_name(name)
#endif

[Gerrit Updater]

Oleg Drokin ([e-mail]) uploaded a new patch: https://review.whamcloud.com/27874
Subject: LU-9698 osd-ldiskfs: See if kallsyms_lookup_name is exported
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 38e08695753f0511c2cab5109a2411ef43495ad1