On Mon, 18 Jun 2007 14:44:57 -0400 Chuck Ebbert <[EMAIL PROTECTED]> wrote:
> > I fancy it's done by the kprobe_page_fault handler, but I do not see > > clearly how writing the breakpoint from arch_arm_kprobe() in > > non-writeable memory is done. > > Looks like it's not merged yet: > > http://lkml.org/lkml/2007/6/7/2 > > This needs to go in before 2.6.22-final Andi, I'll include the below two patches in the next batch, OK? From: "S. P. Prasanna" <[EMAIL PROTECTED]> Fix the problem of page protection introduced by CONFIG_DEBUG_RODATA for x86_64 architecture. As per Andi Kleen's suggestion, the kernel text pages are marked writeable only for a short duration to insert or remove the breakpoints. Signed-off-by: Prasanna S P<[EMAIL PROTECTED]> Acked-by: Jim Keniston <[EMAIL PROTECTED]> Cc: Andi Kleen <[EMAIL PROTECTED]> Signed-off-by: Andrew Morton <[EMAIL PROTECTED]> --- arch/x86_64/kernel/kprobes.c | 26 ++++++++++++++++++++++++++ arch/x86_64/mm/init.c | 6 +++++- include/asm-x86_64/kprobes.h | 10 ++++++++++ 3 files changed, 41 insertions(+), 1 deletion(-) diff -puN arch/x86_64/kernel/kprobes.c~kprobes-x86_64-fix-for-mark-ro-data arch/x86_64/kernel/kprobes.c --- a/arch/x86_64/kernel/kprobes.c~kprobes-x86_64-fix-for-mark-ro-data +++ a/arch/x86_64/kernel/kprobes.c @@ -209,16 +209,42 @@ static void __kprobes arch_copy_kprobe(s void __kprobes arch_arm_kprobe(struct kprobe *p) { + unsigned long addr = (unsigned long)p->addr; + int page_readonly = 0; + + if (kernel_readonly_text(addr)) { + change_page_attr_addr(addr, 1, PAGE_KERNEL_EXEC); + global_flush_tlb(); + page_readonly = 1; + } *p->addr = BREAKPOINT_INSTRUCTION; flush_icache_range((unsigned long) p->addr, (unsigned long) p->addr + sizeof(kprobe_opcode_t)); + if (page_readonly) { + change_page_attr_addr(addr, 1, PAGE_KERNEL_RO); + global_flush_tlb(); + } } void __kprobes arch_disarm_kprobe(struct kprobe *p) { + unsigned long addr = (unsigned long)p->addr; + int page_readonly = 0; + + if (kernel_readonly_text(addr)) { + change_page_attr_addr(addr, 1, PAGE_KERNEL_EXEC); + global_flush_tlb(); + page_readonly = 1; + } + *p->addr = p->opcode; flush_icache_range((unsigned long) p->addr, (unsigned long) p->addr + sizeof(kprobe_opcode_t)); + + if (page_readonly) { + change_page_attr_addr(addr, 1, PAGE_KERNEL_RO); + global_flush_tlb(); + } } void __kprobes arch_remove_kprobe(struct kprobe *p) diff -puN arch/x86_64/mm/init.c~kprobes-x86_64-fix-for-mark-ro-data arch/x86_64/mm/init.c --- a/arch/x86_64/mm/init.c~kprobes-x86_64-fix-for-mark-ro-data +++ a/arch/x86_64/mm/init.c @@ -48,6 +48,7 @@ #define Dprintk(x...) #endif +int kernel_text_is_ro; const struct dma_mapping_ops* dma_ops; EXPORT_SYMBOL(dma_ops); @@ -600,10 +601,13 @@ void mark_rodata_ro(void) { unsigned long start = (unsigned long)_stext, end; + kernel_text_is_ro = 1; #ifdef CONFIG_HOTPLUG_CPU /* It must still be possible to apply SMP alternatives. */ - if (num_possible_cpus() > 1) + if (num_possible_cpus() > 1) { start = (unsigned long)_etext; + kernel_text_is_ro = 0; + } #endif end = (unsigned long)__end_rodata; start = (start + PAGE_SIZE - 1) & PAGE_MASK; diff -puN include/asm-x86_64/kprobes.h~kprobes-x86_64-fix-for-mark-ro-data include/asm-x86_64/kprobes.h --- a/include/asm-x86_64/kprobes.h~kprobes-x86_64-fix-for-mark-ro-data +++ a/include/asm-x86_64/kprobes.h @@ -26,6 +26,7 @@ #include <linux/types.h> #include <linux/ptrace.h> #include <linux/percpu.h> +#include <asm-generic/sections.h> #define __ARCH_WANT_KPROBES_INSN_SLOT @@ -88,4 +89,13 @@ extern int kprobe_handler(struct pt_regs extern int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *data); +extern int kernel_text_is_ro; +static inline int kernel_readonly_text(unsigned long address) +{ + if (kernel_text_is_ro && ((address >= (unsigned long)_stext) + && (address < (unsigned long) _etext))) + return 1; + + return 0; +} #endif /* _ASM_KPROBES_H */ _ From: "S. P. Prasanna" <[EMAIL PROTECTED]> Fix the problem of page protection introduced by CONFIG_DEBUG_RODATA. CONFIG_DEBUG_RODATA marks the text pages as read-only, hence kprobes is unable to insert breakpoints in the kernel text. This patch overrides the page protection when adding or removing a probe for the i386 architecture. Signed-off-by: Prasanna S P<[EMAIL PROTECTED]> Acked-by: Jim Keniston <[EMAIL PROTECTED]> Cc: Andi Kleen <[EMAIL PROTECTED]> Signed-off-by: Andrew Morton <[EMAIL PROTECTED]> --- arch/i386/kernel/kprobes.c | 26 ++++++++++++++++++++++++++ arch/i386/mm/init.c | 2 ++ include/asm-i386/kprobes.h | 12 ++++++++++++ include/asm-i386/pgtable.h | 2 ++ 4 files changed, 42 insertions(+) diff -puN arch/i386/kernel/kprobes.c~kprobes-i386-fix-for-mark-ro-data arch/i386/kernel/kprobes.c --- a/arch/i386/kernel/kprobes.c~kprobes-i386-fix-for-mark-ro-data +++ a/arch/i386/kernel/kprobes.c @@ -169,16 +169,42 @@ int __kprobes arch_prepare_kprobe(struct void __kprobes arch_arm_kprobe(struct kprobe *p) { + unsigned long addr = (unsigned long) p->addr; + int page_readonly = 0; + + if (kernel_readonly_text(addr)) { + page_readonly = 1; + change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RWX); + global_flush_tlb(); + } + *p->addr = BREAKPOINT_INSTRUCTION; flush_icache_range((unsigned long) p->addr, (unsigned long) p->addr + sizeof(kprobe_opcode_t)); + + if (page_readonly) { + change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RX); + global_flush_tlb(); + } } void __kprobes arch_disarm_kprobe(struct kprobe *p) { + unsigned long addr = (unsigned long) p->addr; + int page_readonly = 0; + + if (kernel_readonly_text(addr)) { + page_readonly = 1; + change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RWX); + global_flush_tlb(); + } *p->addr = p->opcode; flush_icache_range((unsigned long) p->addr, (unsigned long) p->addr + sizeof(kprobe_opcode_t)); + if (page_readonly) { + change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RX); + global_flush_tlb(); + } } void __kprobes arch_remove_kprobe(struct kprobe *p) diff -puN arch/i386/mm/init.c~kprobes-i386-fix-for-mark-ro-data arch/i386/mm/init.c --- a/arch/i386/mm/init.c~kprobes-i386-fix-for-mark-ro-data +++ a/arch/i386/mm/init.c @@ -45,6 +45,7 @@ #include <asm/sections.h> #include <asm/paravirt.h> +int kernel_text_is_ro; unsigned int __VMALLOC_RESERVE = 128 << 20; DEFINE_PER_CPU(struct mmu_gather, mmu_gathers); @@ -808,6 +809,7 @@ void mark_rodata_ro(void) change_page_attr(virt_to_page(start), size >> PAGE_SHIFT, PAGE_KERNEL_RX); printk("Write protecting the kernel text: %luk\n", size >> 10); + kernel_text_is_ro = 1; } start += size; diff -puN include/asm-i386/kprobes.h~kprobes-i386-fix-for-mark-ro-data include/asm-i386/kprobes.h --- a/include/asm-i386/kprobes.h~kprobes-i386-fix-for-mark-ro-data +++ a/include/asm-i386/kprobes.h @@ -26,6 +26,8 @@ */ #include <linux/types.h> #include <linux/ptrace.h> +#include <linux/pfn.h> +#include <asm-generic/sections.h> #define __ARCH_WANT_KPROBES_INSN_SLOT @@ -90,4 +92,14 @@ static inline void restore_interrupts(st extern int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *data); +extern int kernel_text_is_ro; +static inline int kernel_readonly_text(unsigned long address) +{ + + if (kernel_text_is_ro && ((address >= PFN_ALIGN(_text)) + && (address < PFN_ALIGN(_etext)))) + return 1; + + return 0; +} #endif /* _ASM_KPROBES_H */ diff -puN include/asm-i386/pgtable.h~kprobes-i386-fix-for-mark-ro-data include/asm-i386/pgtable.h --- a/include/asm-i386/pgtable.h~kprobes-i386-fix-for-mark-ro-data +++ a/include/asm-i386/pgtable.h @@ -159,6 +159,7 @@ void paging_init(void); extern unsigned long long __PAGE_KERNEL, __PAGE_KERNEL_EXEC; #define __PAGE_KERNEL_RO (__PAGE_KERNEL & ~_PAGE_RW) #define __PAGE_KERNEL_RX (__PAGE_KERNEL_EXEC & ~_PAGE_RW) +#define __PAGE_KERNEL_RWX (__PAGE_KERNEL_EXEC | _PAGE_RW) #define __PAGE_KERNEL_NOCACHE (__PAGE_KERNEL | _PAGE_PCD) #define __PAGE_KERNEL_LARGE (__PAGE_KERNEL | _PAGE_PSE) #define __PAGE_KERNEL_LARGE_EXEC (__PAGE_KERNEL_EXEC | _PAGE_PSE) @@ -167,6 +168,7 @@ extern unsigned long long __PAGE_KERNEL, #define PAGE_KERNEL_RO __pgprot(__PAGE_KERNEL_RO) #define PAGE_KERNEL_EXEC __pgprot(__PAGE_KERNEL_EXEC) #define PAGE_KERNEL_RX __pgprot(__PAGE_KERNEL_RX) +#define PAGE_KERNEL_RWX __pgprot(__PAGE_KERNEL_RWX) #define PAGE_KERNEL_NOCACHE __pgprot(__PAGE_KERNEL_NOCACHE) #define PAGE_KERNEL_LARGE __pgprot(__PAGE_KERNEL_LARGE) #define PAGE_KERNEL_LARGE_EXEC __pgprot(__PAGE_KERNEL_LARGE_EXEC) _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
