| Message ID | 1568039433-10176-1-git-send-email-cai@lca.pw |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [v3] powerpc/lockdep: fix a false positive warning | expand |
Hi Qian, Sorry I haven't replied sooner, I've been travelling. Qian Cai <cai@lca.pw> writes: > The commit 108c14858b9e ("locking/lockdep: Add support for dynamic > keys") introduced a boot warning on powerpc below, because since the > commit 2d4f567103ff ("KVM: PPC: Introduce kvm_tmp framework") adds > kvm_tmp[] into the .bss section and then free the rest of unused spaces > back to the page allocator. Thanks for debugging this, but I'd like to fix it differently. kvm_tmp has caused trouble before, with kmemleak, and it can also cause trouble with STRICT_KERNEL_RWX, so I'd like to change how it's done, rather than doing more hacks for it. It should just be a page in text that we use if needed, and don't free, which should avoid all these problems. I'll try and get that done and posted soon. cheers
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h index 4a1664a8658d..6e9e39ebbb27 100644 --- a/arch/powerpc/include/asm/sections.h +++ b/arch/powerpc/include/asm/sections.h @@ -5,8 +5,19 @@ #include <linux/elf.h> #include <linux/uaccess.h> + +#define arch_is_bss_hole arch_is_bss_hole + #include <asm-generic/sections.h> +extern void *bss_hole_start, *bss_hole_end; + +static inline bool arch_is_bss_hole(unsigned long addr) +{ + return addr >= (unsigned long)bss_hole_start && + addr < (unsigned long)bss_hole_end; +} + extern char __head_end[]; #ifdef __powerpc64__ diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c index b7b3a5e4e224..e3c3b076ff07 100644 --- a/arch/powerpc/kernel/kvm.c +++ b/arch/powerpc/kernel/kvm.c @@ -64,9 +64,11 @@ #define KVM_INST_MTSRIN 0x7c0001e4 static bool kvm_patching_worked = true; -char kvm_tmp[1024 * 1024]; static int kvm_tmp_index; +char kvm_tmp[1024 * 1024]; +void *bss_hole_start, *bss_hole_end; + static inline void kvm_patch_ins(u32 *inst, u32 new_inst) { *inst = new_inst; @@ -707,6 +709,10 @@ static __init void kvm_free_tmp(void) */ kmemleak_free_part(&kvm_tmp[kvm_tmp_index], ARRAY_SIZE(kvm_tmp) - kvm_tmp_index); + + bss_hole_start = &kvm_tmp[kvm_tmp_index]; + bss_hole_end = &kvm_tmp[ARRAY_SIZE(kvm_tmp)]; + free_reserved_area(&kvm_tmp[kvm_tmp_index], &kvm_tmp[ARRAY_SIZE(kvm_tmp)], -1, NULL); } diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index d1779d442aa5..28a7a56e7c8a 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -91,6 +91,13 @@ static inline int arch_is_kernel_initmem_freed(unsigned long addr) } #endif +#ifndef arch_is_bss_hole +static inline bool arch_is_bss_hole(unsigned long addr) +{ + return false; +} +#endif + /** * memory_contains - checks if an object is contained within a memory region * @begin: virtual address of the beginning of the memory region diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 4861cf8e274b..cd75b51f15ce 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -675,6 +675,9 @@ static int static_obj(const void *obj) if (arch_is_kernel_initmem_freed(addr)) return 0; + if (arch_is_bss_hole(addr)) + return 0; + /* * static variable? */
The commit 108c14858b9e ("locking/lockdep: Add support for dynamic keys") introduced a boot warning on powerpc below, because since the commit 2d4f567103ff ("KVM: PPC: Introduce kvm_tmp framework") adds kvm_tmp[] into the .bss section and then free the rest of unused spaces back to the page allocator. kernel_init kvm_guest_init kvm_free_tmp free_reserved_area free_unref_page free_unref_page_prepare Later, alloc_workqueue() happens to allocate some pages from there and trigger the warning at, if (WARN_ON_ONCE(static_obj(key))) Fix it by adding a generic helper arch_is_bss_hole() to skip those areas in static_obj(). Since kvm_free_tmp() is only done early during the boot, just go lockless to make the implementation simple for now. WARNING: CPU: 0 PID: 13 at kernel/locking/lockdep.c:1120 Workqueue: events work_for_cpu_fn Call Trace: lockdep_register_key+0x68/0x200 wq_init_lockdep+0x40/0xc0 trunc_msg+0x385f9/0x4c30f (unreliable) wq_init_lockdep+0x40/0xc0 alloc_workqueue+0x1e0/0x620 scsi_host_alloc+0x3d8/0x490 ata_scsi_add_hosts+0xd0/0x220 [libata] ata_host_register+0x178/0x400 [libata] ata_host_activate+0x17c/0x210 [libata] ahci_host_activate+0x84/0x250 [libahci] ahci_init_one+0xc74/0xdc0 [ahci] local_pci_probe+0x78/0x100 work_for_cpu_fn+0x40/0x70 process_one_work+0x388/0x750 process_scheduled_works+0x50/0x90 worker_thread+0x3d0/0x570 kthread+0x1b8/0x1e0 ret_from_kernel_thread+0x5c/0x7c Fixes: 108c14858b9e ("locking/lockdep: Add support for dynamic keys") Signed-off-by: Qian Cai <cai@lca.pw> --- v3: Change arch_is_bss_hole() to return a "bool". Rearrange variables in kvm.c a bit. v2: No need to actually define arch_is_bss_hole() powerpc64 only. arch/powerpc/include/asm/sections.h | 11 +++++++++++ arch/powerpc/kernel/kvm.c | 8 +++++++- include/asm-generic/sections.h | 7 +++++++ kernel/locking/lockdep.c | 3 +++ 4 files changed, 28 insertions(+), 1 deletion(-)