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3cc8ffe43a
[ Upstream commita4c182ecf3] Commit1f9ad21c3b("powerpc/mm: Implement set_memory() routines") included a spin_lock() to change_page_attr() in order to safely perform the three step operations. But then commit9f7853d760("powerpc/mm: Fix set_memory_*() against concurrent accesses") modify it to use pte_update() and do the operation safely against concurrent access. In the meantime, Maxime reported some spinlock recursion. [ 15.351649] BUG: spinlock recursion on CPU#0, kworker/0:2/217 [ 15.357540] lock: init_mm+0x3c/0x420, .magic: dead4ead, .owner: kworker/0:2/217, .owner_cpu: 0 [ 15.366563] CPU: 0 PID: 217 Comm: kworker/0:2 Not tainted 5.15.0+ #523 [ 15.373350] Workqueue: events do_free_init [ 15.377615] Call Trace: [ 15.380232] [e4105ac0] [800946a4] do_raw_spin_lock+0xf8/0x120 (unreliable) [ 15.387340] [e4105ae0] [8001f4ec] change_page_attr+0x40/0x1d4 [ 15.393413] [e4105b10] [801424e0] __apply_to_page_range+0x164/0x310 [ 15.400009] [e4105b60] [80169620] free_pcp_prepare+0x1e4/0x4a0 [ 15.406045] [e4105ba0] [8016c5a0] free_unref_page+0x40/0x2b8 [ 15.411979] [e4105be0] [8018724c] kasan_depopulate_vmalloc_pte+0x6c/0x94 [ 15.418989] [e4105c00] [801424e0] __apply_to_page_range+0x164/0x310 [ 15.425451] [e4105c50] [80187834] kasan_release_vmalloc+0xbc/0x134 [ 15.431898] [e4105c70] [8015f7a8] __purge_vmap_area_lazy+0x4e4/0xdd8 [ 15.438560] [e4105d30] [80160d10] _vm_unmap_aliases.part.0+0x17c/0x24c [ 15.445283] [e4105d60] [801642d0] __vunmap+0x2f0/0x5c8 [ 15.450684] [e4105db0] [800e32d0] do_free_init+0x68/0x94 [ 15.456181] [e4105dd0] [8005d094] process_one_work+0x4bc/0x7b8 [ 15.462283] [e4105e90] [8005d614] worker_thread+0x284/0x6e8 [ 15.468227] [e4105f00] [8006aaec] kthread+0x1f0/0x210 [ 15.473489] [e4105f40] [80017148] ret_from_kernel_thread+0x14/0x1c Remove the read / modify / write sequence to make the operation atomic and remove the spin_lock() in change_page_attr(). To do the operation atomically, we can't use pte modification helpers anymore. Because all platforms have different combination of bits, it is not easy to use those bits directly. But all have the _PAGE_KERNEL_{RO/ROX/RW/RWX} set of flags. All we need it to compare two sets to know which bits are set or cleared. For instance, by comparing _PAGE_KERNEL_ROX and _PAGE_KERNEL_RO you know which bit gets cleared and which bit get set when changing exec permission. Reported-by: Maxime Bizon <mbizon@freebox.fr> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/all/20211212112152.GA27070@sakura/ Link: https://lore.kernel.org/r/43c3c76a1175ae6dc1a3d3b5c3f7ecb48f683eea.1640344012.git.christophe.leroy@csgroup.eu Signed-off-by: Sasha Levin <sashal@kernel.org>
98 lines
2.5 KiB
C
98 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* MMU-generic set_memory implementation for powerpc
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*
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* Copyright 2019-2021, IBM Corporation.
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*/
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#include <linux/mm.h>
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#include <linux/vmalloc.h>
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#include <linux/set_memory.h>
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#include <asm/mmu.h>
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#include <asm/page.h>
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#include <asm/pgtable.h>
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static pte_basic_t pte_update_delta(pte_t *ptep, unsigned long addr,
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unsigned long old, unsigned long new)
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{
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return pte_update(&init_mm, addr, ptep, old & ~new, new & ~old, 0);
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}
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/*
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* Updates the attributes of a page atomically.
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*
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* This sequence is safe against concurrent updates, and also allows updating the
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* attributes of a page currently being executed or accessed.
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*/
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static int change_page_attr(pte_t *ptep, unsigned long addr, void *data)
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{
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long action = (long)data;
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/* modify the PTE bits as desired */
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switch (action) {
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case SET_MEMORY_RO:
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/* Don't clear DIRTY bit */
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pte_update_delta(ptep, addr, _PAGE_KERNEL_RW & ~_PAGE_DIRTY, _PAGE_KERNEL_RO);
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break;
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case SET_MEMORY_RW:
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pte_update_delta(ptep, addr, _PAGE_KERNEL_RO, _PAGE_KERNEL_RW);
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break;
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case SET_MEMORY_NX:
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pte_update_delta(ptep, addr, _PAGE_KERNEL_ROX, _PAGE_KERNEL_RO);
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break;
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case SET_MEMORY_X:
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pte_update_delta(ptep, addr, _PAGE_KERNEL_RO, _PAGE_KERNEL_ROX);
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break;
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case SET_MEMORY_NP:
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pte_update(&init_mm, addr, ptep, _PAGE_PRESENT, 0, 0);
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break;
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case SET_MEMORY_P:
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pte_update(&init_mm, addr, ptep, 0, _PAGE_PRESENT, 0);
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break;
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default:
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WARN_ON_ONCE(1);
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break;
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}
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/* See ptesync comment in radix__set_pte_at() */
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if (radix_enabled())
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asm volatile("ptesync": : :"memory");
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flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
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return 0;
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}
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int change_memory_attr(unsigned long addr, int numpages, long action)
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{
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unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
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unsigned long size = numpages * PAGE_SIZE;
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if (!numpages)
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return 0;
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if (WARN_ON_ONCE(is_vmalloc_or_module_addr((void *)addr) &&
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is_vm_area_hugepages((void *)addr)))
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return -EINVAL;
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#ifdef CONFIG_PPC_BOOK3S_64
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/*
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* On hash, the linear mapping is not in the Linux page table so
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* apply_to_existing_page_range() will have no effect. If in the future
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* the set_memory_* functions are used on the linear map this will need
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* to be updated.
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*/
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if (!radix_enabled()) {
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int region = get_region_id(addr);
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if (WARN_ON_ONCE(region != VMALLOC_REGION_ID && region != IO_REGION_ID))
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return -EINVAL;
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}
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#endif
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return apply_to_existing_page_range(&init_mm, start, size,
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change_page_attr, (void *)action);
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}
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