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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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7
tools/include/linux/static_call_types.h
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@@ -16,6 +16,13 @@
#define STATIC_CALL_TRAMP(name) __PASTE(STATIC_CALL_TRAMP_PREFIX, name)
#define STATIC_CALL_TRAMP_STR(name) __stringify(STATIC_CALL_TRAMP(name))
/*
* Flags in the low bits of static_call_site::key.
*/
#define STATIC_CALL_SITE_TAIL 1UL /* tail call */
#define STATIC_CALL_SITE_INIT 2UL /* init section */
#define STATIC_CALL_SITE_FLAGS 3UL
/*
* The static call site table needs to be created by external tooling (objtool
* or a compiler plugin).