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Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching

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Pull livepatching updates from Jiri Kosina:

 - removal of dead code (Kamalesh Babulal)

 - documentation update (Miroslav Benes)

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching:
  livepatch: doc: remove the limitation for schedule() patching
  powerpc/livepatch: Remove klp_write_module_reloc() stub
This commit is contained in:
Linus Torvalds 2017-02-20 17:13:23 -08:00
commit 59da2a0630
2 changed files with 0 additions and 26 deletions
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19
Documentation/livepatch/livepatch.txt
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@ -329,25 +329,6 @@ The current Livepatch implementation has several limitations:
by "notrace".
+ Anything inlined into __schedule() can not be patched.
The switch_to macro is inlined into __schedule(). It switches the
context between two processes in the middle of the macro. It does
not save RIP in x86_64 version (contrary to 32-bit version). Instead,
the currently used __schedule()/switch_to() handles both processes.
Now, let's have two different tasks. One calls the original
__schedule(), its registers are stored in a defined order and it
goes to sleep in the switch_to macro and some other task is restored
using the original __schedule(). Then there is the second task which
calls patched__schedule(), it goes to sleep there and the first task
is picked by the patched__schedule(). Its RSP is restored and now
the registers should be restored as well. But the order is different
in the new patched__schedule(), so...
There is work in progress to remove this limitation.
+ Livepatch modules can not be removed.
The current implementation just redirects the functions at the very

7
arch/powerpc/include/asm/livepatch.h
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@ -28,13 +28,6 @@ static inline int klp_check_compiler_support(void)
return 0;
}
static inline int klp_write_module_reloc(struct module *mod, unsigned long
type, unsigned long loc, unsigned long value)
{
/* This requires infrastructure changes; we need the loadinfos. */
return -ENOSYS;
}
static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
{
regs->nip = ip;