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static_call: Handle tail-calls

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GCC can turn our static_call(name)(args...) into a tail call, in which
case we get a JMP.d32 into the trampoline (which then does a further
tail-call).

Teach objtool to recognise and mark these in .static_call_sites and
adjust the code patching to deal with this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20200818135805.101186767@infradead.org
This commit is contained in:
Peter Zijlstra
2020-08-18 15:57:49 +02:00
committed by Ingo Molnar
parent 452cddbff7
commit 5b06fd3bb9
6 changed files with 60 additions and 18 deletions
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4
include/linux/static_call.h
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@@ -103,7 +103,7 @@
/*
* Either @site or @tramp can be NULL.
*/
extern void arch_static_call_transform(void *site, void *tramp, void *func);
extern void arch_static_call_transform(void *site, void *tramp, void *func, bool tail);
#define STATIC_CALL_TRAMP_ADDR(name) &STATIC_CALL_TRAMP(name)
@@ -206,7 +206,7 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
{
cpus_read_lock();
WRITE_ONCE(key->func, func);
arch_static_call_transform(NULL, tramp, func);
arch_static_call_transform(NULL, tramp, func, false);
cpus_read_unlock();
}