On Wed, Jul 19 2023 at 11:27:50 PM +0800, Huacai Chen wrote: > Hi, Enze, > > On Wed, Jul 19, 2023 at 4:34 PM Enze Li <lienze@xxxxxxxxxx> wrote: >> >> The LoongArch architecture is quite different from other architectures. >> When the allocating of KFENCE itself is done, it is mapped to the direct >> mapping configuration window [1] by default on LoongArch. It means that >> it is not possible to use the page table mapped mode which required by >> the KFENCE system and therefore it should be remapped to the appropriate >> region. >> >> This patch adds architecture specific implementation details for KFENCE. >> In particular, this implements the required interface in <asm/kfence.h>. >> >> Tested this patch by using the testcases and all passed. >> >> [1] https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#virtual-address-space-and-address-translation-mode >> >> Signed-off-by: Enze Li <lienze@xxxxxxxxxx> >> --- >> arch/loongarch/Kconfig | 1 + >> arch/loongarch/include/asm/kfence.h | 62 ++++++++++++++++++++++++++++ >> arch/loongarch/include/asm/pgtable.h | 6 +++ >> arch/loongarch/mm/fault.c | 22 ++++++---- >> 4 files changed, 83 insertions(+), 8 deletions(-) >> create mode 100644 arch/loongarch/include/asm/kfence.h >> >> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig >> index 5411e3a4eb88..db27729003d3 100644 >> --- a/arch/loongarch/Kconfig >> +++ b/arch/loongarch/Kconfig >> @@ -93,6 +93,7 @@ config LOONGARCH >> select HAVE_ARCH_JUMP_LABEL >> select HAVE_ARCH_JUMP_LABEL_RELATIVE >> select HAVE_ARCH_KASAN >> + select HAVE_ARCH_KFENCE if 64BIT > "if 64BIT" can be dropped here. > Fixed. >> select HAVE_ARCH_MMAP_RND_BITS if MMU >> select HAVE_ARCH_SECCOMP_FILTER >> select HAVE_ARCH_TRACEHOOK >> diff --git a/arch/loongarch/include/asm/kfence.h b/arch/loongarch/include/asm/kfence.h >> new file mode 100644 >> index 000000000000..2a85acc2bc70 >> --- /dev/null >> +++ b/arch/loongarch/include/asm/kfence.h >> @@ -0,0 +1,62 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +/* >> + * KFENCE support for LoongArch. >> + * >> + * Author: Enze Li <lienze@xxxxxxxxxx> >> + * Copyright (C) 2022-2023 KylinSoft Corporation. >> + */ >> + >> +#ifndef _ASM_LOONGARCH_KFENCE_H >> +#define _ASM_LOONGARCH_KFENCE_H >> + >> +#include <linux/kfence.h> >> +#include <asm/pgtable.h> >> +#include <asm/tlb.h> >> + >> +static inline char *arch_kfence_init_pool(void) >> +{ >> + char *__kfence_pool_orig = __kfence_pool; > I prefer kfence_pool than __kfence_pool_orig here. > Fixed. >> + struct vm_struct *area; >> + int err; >> + >> + area = __get_vm_area_caller(KFENCE_POOL_SIZE, VM_IOREMAP, >> + KFENCE_AREA_START, KFENCE_AREA_END, >> + __builtin_return_address(0)); >> + if (!area) >> + return NULL; >> + >> + __kfence_pool = (char *)area->addr; >> + err = ioremap_page_range((unsigned long)__kfence_pool, >> + (unsigned long)__kfence_pool + KFENCE_POOL_SIZE, >> + virt_to_phys((void *)__kfence_pool_orig), >> + PAGE_KERNEL); >> + if (err) { >> + free_vm_area(area); >> + return NULL; >> + } >> + >> + return __kfence_pool; >> +} >> + >> +/* Protect the given page and flush TLB. */ >> +static inline bool kfence_protect_page(unsigned long addr, bool protect) >> +{ >> + pte_t *pte = virt_to_kpte(addr); >> + >> + if (WARN_ON(!pte) || pte_none(*pte)) >> + return false; >> + >> + if (protect) >> + set_pte(pte, __pte(pte_val(*pte) & ~(_PAGE_VALID | _PAGE_PRESENT))); >> + else >> + set_pte(pte, __pte(pte_val(*pte) | (_PAGE_VALID | _PAGE_PRESENT))); >> + >> + /* Flush this CPU's TLB. */ >> + preempt_disable(); >> + local_flush_tlb_one(addr); >> + preempt_enable(); >> + >> + return true; >> +} >> + >> +#endif /* _ASM_LOONGARCH_KFENCE_H */ >> diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h >> index 0fc074b8bd48..5a9c81298fe3 100644 >> --- a/arch/loongarch/include/asm/pgtable.h >> +++ b/arch/loongarch/include/asm/pgtable.h >> @@ -85,7 +85,13 @@ extern unsigned long zero_page_mask; >> #define MODULES_VADDR (vm_map_base + PCI_IOSIZE + (2 * PAGE_SIZE)) >> #define MODULES_END (MODULES_VADDR + SZ_256M) >> >> +#ifdef CONFIG_KFENCE >> +#define KFENCE_AREA_START MODULES_END >> +#define KFENCE_AREA_END (KFENCE_AREA_START + SZ_512M) > Why you choose 512M here? > One day I noticed that 512M can hold 16K (default 255) KFENCE objects, which should be more than enough and I think this should be appropriate. As far as I see, KFENCE system does not have the upper limit of this value(CONFIG_KFENCE_NUM_OBJECTS), which could theoretically be any number. There's another way, how about setting this value to be determined by the configuration, like this, ======================================================================== +#define KFENCE_AREA_END \ + (KFENCE_AREA_START + (CONFIG_KFENCE_NUM_OBJECTS + 1) * 2 * PAGE_SIZE) ======================================================================== >> +#define VMALLOC_START KFENCE_AREA_END >> +#else >> #define VMALLOC_START MODULES_END >> +#endif > I don't like to put KFENCE_AREA between module and vmalloc range (it > may cause some problems), can we put it after vmemmap? I found that there is not enough space after vmemmap and that these spaces are affected by KASAN. As follows, Without KASAN ###### module 0xffff800002008000~0xffff800012008000 ###### malloc 0xffff800032008000~0xfffffefffe000000 ###### vmemmap 0xffffff0000000000~0xffffffffffffffff With KASAN ###### module 0xffff800002008000~0xffff800012008000 ###### malloc 0xffff800032008000~0xffffbefffe000000 ###### vmemmap 0xffffbf0000000000~0xffffbfffffffffff What about put it before MODULES_START? ============================================================================ --- a/arch/loongarch/include/asm/pgtable.h +++ b/arch/loongarch/include/asm/pgtable.h @@ -82,7 +82,14 @@ extern unsigned long zero_page_mask; * Avoid the first couple of pages so NULL pointer dereferences will * still reliably trap. */ +#ifdef CONFIG_KFENCE +#define KFENCE_AREA_START (vm_map_base + PCI_IOSIZE + (2 * PAGE_SIZE)) +#define KFENCE_AREA_END \ + (KFENCE_AREA_START + (CONFIG_KFENCE_NUM_OBJECTS + 1) * 2 * PAGE_SIZE) +#define MODULES_VADDR KFENCE_AREA_END +#else #define MODULES_VADDR (vm_map_base + PCI_IOSIZE + (2 * PAGE_SIZE)) +#endif #define MODULES_END (MODULES_VADDR + SZ_256M) ============================================================================ Best Regards, Enze >> >> #ifndef CONFIG_KASAN >> #define VMALLOC_END \ >> diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c >> index da5b6d518cdb..c0319128b221 100644 >> --- a/arch/loongarch/mm/fault.c >> +++ b/arch/loongarch/mm/fault.c >> @@ -23,6 +23,7 @@ >> #include <linux/kprobes.h> >> #include <linux/perf_event.h> >> #include <linux/uaccess.h> >> +#include <linux/kfence.h> >> >> #include <asm/branch.h> >> #include <asm/mmu_context.h> >> @@ -30,7 +31,8 @@ >> >> int show_unhandled_signals = 1; >> >> -static void __kprobes no_context(struct pt_regs *regs, unsigned long address) >> +static void __kprobes no_context(struct pt_regs *regs, unsigned long address, >> + unsigned long write) >> { >> const int field = sizeof(unsigned long) * 2; >> >> @@ -38,6 +40,9 @@ static void __kprobes no_context(struct pt_regs *regs, unsigned long address) >> if (fixup_exception(regs)) >> return; >> >> + if (kfence_handle_page_fault(address, write, regs)) >> + return; >> + >> /* >> * Oops. The kernel tried to access some bad page. We'll have to >> * terminate things with extreme prejudice. >> @@ -51,14 +56,15 @@ static void __kprobes no_context(struct pt_regs *regs, unsigned long address) >> die("Oops", regs); >> } >> >> -static void __kprobes do_out_of_memory(struct pt_regs *regs, unsigned long address) >> +static void __kprobes do_out_of_memory(struct pt_regs *regs, unsigned long address, >> + unsigned long write) >> { >> /* >> * We ran out of memory, call the OOM killer, and return the userspace >> * (which will retry the fault, or kill us if we got oom-killed). >> */ >> if (!user_mode(regs)) { >> - no_context(regs, address); >> + no_context(regs, address, write); >> return; >> } >> pagefault_out_of_memory(); >> @@ -69,7 +75,7 @@ static void __kprobes do_sigbus(struct pt_regs *regs, >> { >> /* Kernel mode? Handle exceptions or die */ >> if (!user_mode(regs)) { >> - no_context(regs, address); >> + no_context(regs, address, write); >> return; >> } >> >> @@ -90,7 +96,7 @@ static void __kprobes do_sigsegv(struct pt_regs *regs, >> >> /* Kernel mode? Handle exceptions or die */ >> if (!user_mode(regs)) { >> - no_context(regs, address); >> + no_context(regs, address, write); >> return; >> } >> >> @@ -149,7 +155,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, >> */ >> if (address & __UA_LIMIT) { >> if (!user_mode(regs)) >> - no_context(regs, address); >> + no_context(regs, address, write); >> else >> do_sigsegv(regs, write, address, si_code); >> return; >> @@ -211,7 +217,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, >> >> if (fault_signal_pending(fault, regs)) { >> if (!user_mode(regs)) >> - no_context(regs, address); >> + no_context(regs, address, write); >> return; >> } >> >> @@ -232,7 +238,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, >> if (unlikely(fault & VM_FAULT_ERROR)) { >> mmap_read_unlock(mm); >> if (fault & VM_FAULT_OOM) { >> - do_out_of_memory(regs, address); >> + do_out_of_memory(regs, address, write); >> return; >> } else if (fault & VM_FAULT_SIGSEGV) { >> do_sigsegv(regs, write, address, si_code); >> -- >> 2.34.1 >> >>
