[PATCH 5/9] arm64: alternatives: make alt_region const

Mark Rutland
2022-09-01T15:16:50Z

We never alter a struct alt_region after creation, and we open-code the
bounds of the kernel alternatives region in two functions.

This patch adds a shared struct alt_region, and marks the alt regions as
const to prevent unintentional modification.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
---
arch/arm64/kernel/alternative.c | 26 ++++++++++++--------------
1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index d94d97cb4a0bf..2e18c9c0f612b 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -133,8 +133,9 @@ static void clean_dcache_range_nopatch(u64 start, u64 end)
} while (cur += d_size, cur < end);
}

-static void __nocfi __apply_alternatives(struct alt_region *region, bool is_module,
- unsigned long *feature_mask)
+static void __nocfi __apply_alternatives(const struct alt_region *region,
+ bool is_module,
+ unsigned long *feature_mask)
{
struct alt_instr *alt;
__le32 *origptr, *updptr;
@@ -190,17 +191,17 @@ static void __nocfi __apply_alternatives(struct alt_region *region, bool is_modu
}
}

+static const struct alt_region kernel_alternatives = {
+ .begin = (struct alt_instr *)__alt_instructions,
+ .end = (struct alt_instr *)__alt_instructions_end,
+};
+
/*
* We might be patching the stop_machine state machine, so implement a
* really simple polling protocol here.
*/
static int __apply_alternatives_multi_stop(void *unused)
{
- struct alt_region region = {
- .begin = (struct alt_instr *)__alt_instructions,
- .end = (struct alt_instr *)__alt_instructions_end,
- };
-
/* We always have a CPU 0 at this point (__init) */
if (smp_processor_id()) {
while (!all_alternatives_applied)
@@ -213,7 +214,8 @@ static int __apply_alternatives_multi_stop(void *unused)
ARM64_NPATCHABLE);

BUG_ON(all_alternatives_applied);
- __apply_alternatives(&region, false, remaining_capabilities);
+ __apply_alternatives(&kernel_alternatives, false,
+ remaining_capabilities);
/* Barriers provided by the cache flushing */
all_alternatives_applied = 1;
}
@@ -236,17 +238,13 @@ void __init apply_alternatives_all(void)
*/
void __init apply_boot_alternatives(void)
{
- struct alt_region region = {
- .begin = (struct alt_instr *)__alt_instructions,
- .end = (struct alt_instr *)__alt_instructions_end,
- };
-
/* If called on non-boot cpu things could go wrong */
WARN_ON(smp_processor_id() != 0);

pr_info("applying boot alternatives\n");

- __apply_alternatives(&region, false, &boot_capabilities[0]);
+ __apply_alternatives(&kernel_alternatives, false,
+ &boot_capabilities[0]);
}

#ifdef CONFIG_MODULES