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ANDROID: init: ensure initcall ordering with LTO

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With LTO, the compiler doesn't necessarily obey link order for
initcalls, and the initcall variables need to be globally unique
to avoid naming collisions.

In order to preserve the intended order, this change moves each
initcall variable into its own section and generates a linker
script (in scripts/link-vmlinux.sh) to define the correct order
for these sections. We also add a __COUNTER__ prefix to the name,
so we can retain the order of initcalls within each compilation
unit, and __LINE__ to help ensure uniqueness.

Bug: 145210207
Change-Id: I602038783853497790c5a2941343c546e380c525
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
This commit is contained in:
Sami Tolvanen
2017-12-08 15:49:24 -08:00
parent e39cebad64
commit ae14b5c962
3 changed files with 294 additions and 20 deletions
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26
include/linux/init.h
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@@ -192,10 +192,32 @@ extern bool initcall_debug;
".long " #fn " - . \n" \
".previous \n");
#else
#define ___define_initcall(fn, id, __sec) \
#ifdef CONFIG_LTO_CLANG
/*
* With LTO, the compiler doesn't necessarily obey link order for
* initcalls, and the initcall variable needs to be globally unique
* to avoid naming collisions. In order to preserve the correct
* order, we add each variable into its own section and generate a
* linker script (in scripts/link-vmlinux.sh) to ensure the order
* remains correct. We also add a __COUNTER__ prefix to the name,
* so we can retain the order of initcalls within each compilation
* unit, and __LINE__ to make the names more unique.
*/
#define ___lto_initcall(c, l, fn, id, __sec) \
static initcall_t __initcall_##c##_##l##_##fn##id __used \
__attribute__((__section__( #__sec \
__stringify(.init..##c##_##l##_##fn)))) = fn;
#define __lto_initcall(c, l, fn, id, __sec) \
___lto_initcall(c, l, fn, id, __sec)
#define ___define_initcall(fn, id, __sec) \
__lto_initcall(__COUNTER__, __LINE__, fn, id, __sec)
#else
#define ___define_initcall(fn, id, __sec) \
static initcall_t __initcall_##fn##id __used \
__attribute__((__section__(#__sec ".init"))) = fn;
#endif
#endif
#define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
@@ -236,7 +258,7 @@ extern bool initcall_debug;
#define __exitcall(fn) \
static exitcall_t __exitcall_##fn __exit_call = fn
#define console_initcall(fn) ___define_initcall(fn,, .con_initcall)
#define console_initcall(fn) ___define_initcall(fn, con, .con_initcall)
struct obs_kernel_param {
const char *str;