The current initialization of the per-cpu offset register is difficult
to follow and this initialization is not always early enough for
upcoming instrumentation with KCSAN, where the instrumentation callbacks
use the per-cpu offset.
To make it possible to support KCSAN, and to simplify reasoning about
early bringup code, let's initialize the per-cpu offset earlier, before
we run any C code that may consume it. To do so, this patch adds a new
init_this_cpu_offset() helper that's called before the usual
primary/secondary start functions. For consistency, this is also used to
re-initialize the per-cpu offset after the runtime per-cpu areas have
been allocated (which can change CPU0's offset).
So that init_this_cpu_offset() isn't subject to any instrumentation that
might consume the per-cpu offset, it is marked with noinstr, preventing
instrumentation.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201005164303.21389-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
void update_cpu_features(int cpu, struct cpuinfo_arm64 *info,
struct cpuinfo_arm64 *boot);
+void init_this_cpu_offset(void);
+
#endif /* __ASM_CPU_H */
bl __pi_memset
dsb ishst // Make zero page visible to PTW
+ bl init_this_cpu_offset
+
#ifdef CONFIG_KASAN
bl kasan_early_init
#endif
ptrauth_keys_init_cpu x2, x3, x4, x5
#endif
+ bl init_this_cpu_offset
b secondary_start_kernel
SYM_FUNC_END(__secondary_switched)
u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
set_cpu_logical_map(0, mpidr);
- /*
- * clear __my_cpu_offset on boot CPU to avoid hang caused by
- * using percpu variable early, for example, lockdep will
- * access percpu variable inside lock_release
- */
- set_my_cpu_offset(0);
pr_info("Booting Linux on physical CPU 0x%010lx [0x%08x]\n",
(unsigned long)mpidr, read_cpuid_id());
}
}
EXPORT_SYMBOL_GPL(cpu_logical_map);
+void noinstr init_this_cpu_offset(void)
+{
+ unsigned int cpu = task_cpu(current);
+ set_my_cpu_offset(per_cpu_offset(cpu));
+}
+
void __init __no_sanitize_address setup_arch(char **cmdline_p)
{
init_mm.start_code = (unsigned long) _text;
u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
struct mm_struct *mm = &init_mm;
const struct cpu_operations *ops;
- unsigned int cpu;
-
- cpu = task_cpu(current);
- set_my_cpu_offset(per_cpu_offset(cpu));
+ unsigned int cpu = smp_processor_id();
/*
* All kernel threads share the same mm context; grab a
void __init smp_prepare_boot_cpu(void)
{
- set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
+ /*
+ * Now that setup_per_cpu_areas() has allocated the runtime per-cpu
+ * areas it is only safe to read the CPU0 boot-time area, and we must
+ * reinitialize the offset to point to the runtime area.
+ */
+ init_this_cpu_offset();
+
cpuinfo_store_boot_cpu();
/*