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Re: Kernel for Spectre and Meltdown






On 30 January 2018 at 15:23, Elimar Riesebieter <riesebie@xxxxxxxx> wrote:
* rhkramer@xxxxxxxxx <rhkramer@xxxxxxxxx> [2018-01-29 10:47 -0500]:

[...]
> On the other hand, if I download kernel source, I would need GCC, and a
> version that is sufficient for the code.

One can check the compiler version the running kernel is built with
by:

$ cat /proc/version
Linux version 4.14.15-toy-lxtec-amd64 (riesebie@toy) (gcc version 7.3.0 (Debian 7.3.0-1)) #1 SMP Tue Jan 30 14:20:49 CET 2018

​That is a very useful command.

I ran it myself.

djt /home/mikef/spectre-meltdown-checker # cat /proc/version
Linux version 4.14.14-gentoo (root@djt) (gcc version 7.2.0 (Gentoo 7.2.0-r1)) #1 SMP Tue Jan 23 13:06:23 GMT 2018

Here is a bit of the output from the spectre patch checker:


​* Mitigation 2
  * Kernel compiled with retpoline option:  YES
  * Kernel compiled with a retpoline-aware compiler:  NO  (kernel reports minimal retpoline compilation)
  * Retpoline enabled:  YES
> STATUS:  VULNERABLE  (Vulnerable: Minimal AMD ASM retpoline)

​As can be seen here, the compiler I used to create this kernel was not recent enough to make retpoline work.

Since I now have gcc 7.3 installed I will do kernel upgrade in a little while and see if I can change the NO in

  "* Kernel compiled with a retpoline-aware compiler:  NO  (kernel reports minimal retpoline compilation)"

to YES.....

I think it will work.

Cheers MF








 
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Elimar
--
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