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init: lto: ensure initcall ordering

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

This change exports __KBUILD_MODNAME and adds the initcall_id() macro,
which uses it together with __COUNTER__ and __LINE__ to help ensure
these variables have unique names, and moves each variable to its own
section when LTO is enabled, so the correct order can be specified using
a linker script.

The generate_initcall_ordering.pl script uses nm to find initcalls from
the object files passed to the linker, and generates a linker script
that specifies the same order for initcalls that we would have without
LTO. With LTO enabled, the script is called in link-vmlinux.sh through
jobserver-exec to limit the number of jobs spawned.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-8-samitolvanen@google.com
This commit is contained in:
Sami Tolvanen
2020-12-11 10:46:24 -08:00
committed by Kees Cook
parent fbe078d397
commit a8cccdd954
4 changed files with 334 additions and 9 deletions
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52
include/linux/init.h
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@@ -184,19 +184,57 @@ extern bool initcall_debug;
* as KEEP() in the linker script.
*/
/* Format: <modname>__<counter>_<line>_<fn> */
#define __initcall_id(fn) \
__PASTE(__KBUILD_MODNAME, \
__PASTE(__, \
__PASTE(__COUNTER__, \
__PASTE(_, \
__PASTE(__LINE__, \
__PASTE(_, fn))))))
/* Format: __<prefix>__<iid><id> */
#define __initcall_name(prefix, __iid, id) \
__PASTE(__, \
__PASTE(prefix, \
__PASTE(__, \
__PASTE(__iid, id))))
#ifdef CONFIG_LTO_CLANG
/*
* With LTO, the compiler doesn't necessarily obey link order for
* initcalls. 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 specify the order of the sections.
*/
#define __initcall_section(__sec, __iid) \
#__sec ".init.." #__iid
#else
#define __initcall_section(__sec, __iid) \
#__sec ".init"
#endif
#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
#define ___define_initcall(fn, id, __sec) \
#define ____define_initcall(fn, __name, __sec) \
__ADDRESSABLE(fn) \
asm(".section \"" #__sec ".init\", \"a\" \n" \
"__initcall_" #fn #id ": \n" \
asm(".section \"" __sec "\", \"a\" \n" \
__stringify(__name) ": \n" \
".long " #fn " - . \n" \
".previous \n");
#else
#define ___define_initcall(fn, id, __sec) \
static initcall_t __initcall_##fn##id __used \
__attribute__((__section__(#__sec ".init"))) = fn;
#define ____define_initcall(fn, __name, __sec) \
static initcall_t __name __used \
__attribute__((__section__(__sec))) = fn;
#endif
#define __unique_initcall(fn, id, __sec, __iid) \
____define_initcall(fn, \
__initcall_name(initcall, __iid, id), \
__initcall_section(__sec, __iid))
#define ___define_initcall(fn, id, __sec) \
__unique_initcall(fn, id, __sec, __initcall_id(fn))
#define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
/*
@@ -236,7 +274,7 @@ 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;