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Subject[PATCH] init: Initialize jump labels before command line option parsing
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When a module option, or core kernel argument, toggles a static-key it
requires jump labels to be initialized early. While x86, PowerPC, and
ARM64 arrange for jump_label_init() to be called before parse_args(),
ARM does not.

Kernel command line: rdinit=/sbin/init page_alloc.shuffle=1 panic=-1 console=ttyAMA0,115200 page_alloc.shuffle=1
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at ./include/linux/jump_label.h:303
page_alloc_shuffle+0x12c/0x1ac
static_key_enable(): static key 'page_alloc_shuffle_key+0x0/0x4' used
before call to jump_label_init()
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted
5.1.0-rc4-next-20190410-00003-g3367c36ce744 #1
Hardware name: ARM Integrator/CP (Device Tree)
[<c0011c68>] (unwind_backtrace) from [<c000ec48>] (show_stack+0x10/0x18)
[<c000ec48>] (show_stack) from [<c07e9710>] (dump_stack+0x18/0x24)
[<c07e9710>] (dump_stack) from [<c001bb1c>] (__warn+0xe0/0x108)
[<c001bb1c>] (__warn) from [<c001bb88>] (warn_slowpath_fmt+0x44/0x6c)
[<c001bb88>] (warn_slowpath_fmt) from [<c0b0c4a8>]
(page_alloc_shuffle+0x12c/0x1ac)
[<c0b0c4a8>] (page_alloc_shuffle) from [<c0b0c550>] (shuffle_store+0x28/0x48)
[<c0b0c550>] (shuffle_store) from [<c003e6a0>] (parse_args+0x1f4/0x350)
[<c003e6a0>] (parse_args) from [<c0ac3c00>] (start_kernel+0x1c0/0x488)

Move the fallback call to jump_label_init() to occur before
parse_args(). The redundant calls to jump_label_init() in other archs
are left intact in case they have static key toggling use cases that are
even earlier than option parsing.

Reported-by: Guenter Roeck <groeck@google.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
init/main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/init/main.c b/init/main.c
index 598e278b46f7..7d4025d665eb 100644
--- a/init/main.c
+++ b/init/main.c
@@ -582,6 +582,8 @@ asmlinkage __visible void __init start_kernel(void)
page_alloc_init();

pr_notice("Kernel command line: %s\n", boot_command_line);
+ /* parameters may set static keys */
+ jump_label_init();
parse_early_param();
after_dashes = parse_args("Booting kernel",
static_command_line, __start___param,
@@ -591,8 +593,6 @@ asmlinkage __visible void __init start_kernel(void)
parse_args("Setting init args", after_dashes, NULL, 0, -1, -1,
NULL, set_init_arg);

- jump_label_init();
-
/*
* These use large bootmem allocations and must precede
* kmem_cache_init()
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