| Message ID | 20220711030653.150950-2-npiggin@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | [1/2] powerpc/mce: mce_init use early_cpu_to_node | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 7 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 23 jobs. |
Nicholas Piggin <npiggin@gmail.com> writes: > If the boot CPU tries to access per-cpu data of other CPUs before > per cpu areas are set up, it will unexpectedly use offset 0. > > Try to catch such accesses by poisoning the __per_cpu_offset array. I wasn't sure about this. On bare metal it's just an instant checkstop which is very user hostile. I worry it's just going to cause unusual configurations/options to crash for folks, like eg. booting with page_poison=1 did a while back. Can we put it behind a debug option? Maybe CONFIG_DEBUG_VM ? cheers
diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h index 8e5b7d0b851c..6ca1a9fc5725 100644 --- a/arch/powerpc/include/asm/percpu.h +++ b/arch/powerpc/include/asm/percpu.h @@ -7,6 +7,7 @@ * Same as asm-generic/percpu.h, except that we store the per cpu offset * in the paca. Based on the x86-64 implementation. */ +#define PER_CPU_OFFSET_POISON 0xfeeeeeeeeeeeeeeeULL #ifdef CONFIG_SMP diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c index ba593fd60124..914d27c8b84a 100644 --- a/arch/powerpc/kernel/paca.c +++ b/arch/powerpc/kernel/paca.c @@ -223,7 +223,7 @@ void __init initialise_paca(struct paca_struct *new_paca, int cpu) new_paca->hw_cpu_id = 0xffff; new_paca->kexec_state = KEXEC_STATE_NONE; new_paca->__current = &init_task; - new_paca->data_offset = 0xfeeeeeeeeeeeeeeeULL; + new_paca->data_offset = PER_CPU_OFFSET_POISON; #ifdef CONFIG_PPC_64S_HASH_MMU new_paca->slb_shadow_ptr = NULL; #endif diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 5761f08dae95..60f0d1258526 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -812,7 +812,7 @@ static __init int pcpu_cpu_to_node(int cpu) return early_cpu_to_node(cpu); } -unsigned long __per_cpu_offset[NR_CPUS] __read_mostly; +unsigned long __per_cpu_offset[NR_CPUS] __read_mostly = { [0 ... NR_CPUS-1 ] = PER_CPU_OFFSET_POISON }; EXPORT_SYMBOL(__per_cpu_offset); void __init setup_per_cpu_areas(void)
If the boot CPU tries to access per-cpu data of other CPUs before per cpu areas are set up, it will unexpectedly use offset 0. Try to catch such accesses by poisoning the __per_cpu_offset array. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/include/asm/percpu.h | 1 + arch/powerpc/kernel/paca.c | 2 +- arch/powerpc/kernel/setup_64.c | 2 +- 3 files changed, 3 insertions(+), 2 deletions(-)