linux-kernel - [PATCH] arm64: Initialize jump labels before setup_machine

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Message-Id: <20220602022109.780348-1-swboyd@chromium.org>
Date:   Wed,  1 Jun 2022 19:21:09 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: [PATCH] arm64: Initialize jump labels before setup_machine_fdt()

A static key warning splat appears during early boot on arm64 systems
that credit randomness from devicetrees that contain an "rng-seed"
property. This is because setup_machine_fdt() is called before
jump_label_init() during setup_arch(). Let's swap the order of these two
calls so that jump labels are initialized before the devicetree is
unflattened and the rng seed is credited.

 static_key_enable_cpuslocked(): static key '0xffffffe51c6fcfc0' used before call to jump_label_init()
 WARNING: CPU: 0 PID: 0 at kernel/jump_label.c:166 static_key_enable_cpuslocked+0xb0/0xb8
 Modules linked in:
 CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0+ #224 44b43e377bfc84bc99bb5ab885ff694984ee09ff
 pstate: 600001c9 (nZCv dAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : static_key_enable_cpuslocked+0xb0/0xb8
 lr : static_key_enable_cpuslocked+0xb0/0xb8
 sp : ffffffe51c393cf0
 x29: ffffffe51c393cf0 x28: 000000008185054c x27: 00000000f1042f10
 x26: 0000000000000000 x25: 00000000f10302b2 x24: 0000002513200000
 x23: 0000002513200000 x22: ffffffe51c1c9000 x21: fffffffdfdc00000
 x20: ffffffe51c2f0831 x19: ffffffe51c6fcfc0 x18: 00000000ffff1020
 x17: 00000000e1e2ac90 x16: 00000000000000e0 x15: ffffffe51b710708
 x14: 0000000000000066 x13: 0000000000000018 x12: 0000000000000000
 x11: 0000000000000000 x10: 00000000ffffffff x9 : 0000000000000000
 x8 : 0000000000000000 x7 : 61632065726f6665 x6 : 6220646573752027
 x5 : ffffffe51c641d25 x4 : ffffffe51c13142c x3 : ffff0a00ffffff05
 x2 : 40000000ffffe003 x1 : 00000000000001c0 x0 : 0000000000000065
 Call trace:
  static_key_enable_cpuslocked+0xb0/0xb8
  static_key_enable+0x2c/0x40
  crng_set_ready+0x24/0x30
  execute_in_process_context+0x80/0x90
  _credit_init_bits+0x100/0x154
  add_bootloader_randomness+0x64/0x78
  early_init_dt_scan_chosen+0x140/0x184
  early_init_dt_scan_nodes+0x28/0x4c
  early_init_dt_scan+0x40/0x44
  setup_machine_fdt+0x7c/0x120
  setup_arch+0x74/0x1d8
  start_kernel+0x84/0x44c
  __primary_switched+0xc0/0xc8
 ---[ end trace 0000000000000000 ]---
 random: crng init done
 Machine model: Google Lazor (rev1 - 2) with LTE

Cc: Hsin-Yi Wang <hsinyi@...omium.org>
Cc: Douglas Anderson <dianders@...omium.org>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Jason A. Donenfeld <Jason@...c4.com>
Cc: Dominik Brodowski <linux@...inikbrodowski.net>
Fixes: f5bda35fba61 ("random: use static branch for crng_ready()")
Signed-off-by: Stephen Boyd <swboyd@...omium.org>
---
 arch/arm64/kernel/setup.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index fea3223704b6..cf3a759f10d4 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -303,13 +303,14 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
 	early_fixmap_init();
 	early_ioremap_init();
 
-	setup_machine_fdt(__fdt_pointer);
-
 	/*
 	 * Initialise the static keys early as they may be enabled by the
-	 * cpufeature code and early parameters.
+	 * cpufeature code, early parameters, and DT setup.
 	 */
 	jump_label_init();
+
+	setup_machine_fdt(__fdt_pointer);
+
 	parse_early_param();
 
 	/*
-- 
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