On 10/2/18 5:12 PM, Qing Zhao wrote:
On Oct 2, 2018, at 9:55 AM, Martin Liška <mliska@xxxxxxx <mailto:mliska@xxxxxxx>> wrote:
Affected functions: 5
__ilog2_u64/132 (include/linux/log2.h:40:5)
ablkcipher_request_alloc/1639 (include/linux/crypto.h:979:82)
ablkcipher_request_alloc.constprop.8/3198 (include/linux/crypto.h:979:82)
helper_rfc4106_decrypt/3007 (arch/x86/crypto/aesni-intel_glue.c:1016:12)
helper_rfc4106_encrypt/3006 (arch/x86/crypto/aesni-intel_glue.c:939:12)
[..skipped..]
if we want to patch the function “fls64/63”, what else functions we need to patch, too? my guess is:
Hi.
Yes, 'Affected functions' is exactly the list of functions you want to patch.
**all the callers:
__ilog2_u64/132
ablkcipher_request_alloc/1639
helper_rfc4106_decrypt/3007
helper_rfc4106_encrypt/3006
**and:
ablkcipher_request_alloc.constprop.8/3198
is the above correct?
how to generate patch for ablkcipher_request_alloc.constprop.8/3198? since it’s not a function in the source code?
Well, it's a 'static inline' function in a header file thus the function will be inlined in all usages.
In this particular case there's no such caller function, so you're fine.
So, for cloned functions, you have to analyze them case by case manually to see their callers?
No, the tool should provide complete list of affected functions.
So, the tool will provide the callers of the cloned routine?
No, the tool does not list callers of affected functions. But function call ABI is reasonable
live-patching boundary.
then we will patch the callers of the cloned routine, Not the cloned routine itself?
why not just disable ipa-cp or ipa-sra completely?
Because the optimizations create function clones, which are trackable with my tool
and one knows then all affected functions.
Okay. I see.
You can disable the optimizations, but you'll miss some performance benefit provide
by compiler.
Note that as Martin Jambor mentioned in point 2) there are also IPA optimizations that
do not create clones. These should be listed and eventually disabled for kernel live
patching.
Yes, such IPA analyzes should be disabled. we need to identify a complete list of such analyzes.
That was promised to be done by Honza Hubička. He's very skilled in IPA optimizations and he's aware
of optimizations that cause troubles for live-patching.
Martin
thanks.
Qing
