diff options
| -rw-r--r-- | arch/x86/include/asm/shstk.h | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/shstk.c | 5 | ||||
| -rw-r--r-- | arch/x86/kernel/uprobes.c | 117 | ||||
| -rw-r--r-- | include/linux/uprobes.h | 3 | ||||
| -rw-r--r-- | kernel/events/uprobes.c | 24 |
5 files changed, 144 insertions, 7 deletions
diff --git a/arch/x86/include/asm/shstk.h b/arch/x86/include/asm/shstk.h index 896909f306e3..4cb77e004615 100644 --- a/arch/x86/include/asm/shstk.h +++ b/arch/x86/include/asm/shstk.h @@ -22,6 +22,7 @@ void shstk_free(struct task_struct *p); int setup_signal_shadow_stack(struct ksignal *ksig); int restore_signal_shadow_stack(void); int shstk_update_last_frame(unsigned long val); +bool shstk_is_enabled(void); #else static inline long shstk_prctl(struct task_struct *task, int option, unsigned long arg2) { return -EINVAL; } @@ -33,6 +34,7 @@ static inline void shstk_free(struct task_struct *p) {} static inline int setup_signal_shadow_stack(struct ksignal *ksig) { return 0; } static inline int restore_signal_shadow_stack(void) { return 0; } static inline int shstk_update_last_frame(unsigned long val) { return 0; } +static inline bool shstk_is_enabled(void) { return false; } #endif /* CONFIG_X86_USER_SHADOW_STACK */ #endif /* __ASSEMBLY__ */ diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index 9797d4cdb78a..059685612362 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -588,3 +588,8 @@ int shstk_update_last_frame(unsigned long val) ssp = get_user_shstk_addr(); return write_user_shstk_64((u64 __user *)ssp, (u64)val); } + +bool shstk_is_enabled(void) +{ + return features_enabled(ARCH_SHSTK_SHSTK); +} diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index 6402fb3089d2..5a952c5ea66b 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -12,6 +12,7 @@ #include <linux/ptrace.h> #include <linux/uprobes.h> #include <linux/uaccess.h> +#include <linux/syscalls.h> #include <linux/kdebug.h> #include <asm/processor.h> @@ -308,6 +309,122 @@ static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool } #ifdef CONFIG_X86_64 + +asm ( + ".pushsection .rodata\n" + ".global uretprobe_trampoline_entry\n" + "uretprobe_trampoline_entry:\n" + "pushq %rax\n" + "pushq %rcx\n" + "pushq %r11\n" + "movq $" __stringify(__NR_uretprobe) ", %rax\n" + "syscall\n" + ".global uretprobe_syscall_check\n" + "uretprobe_syscall_check:\n" + "popq %r11\n" + "popq %rcx\n" + + /* The uretprobe syscall replaces stored %rax value with final + * return address, so we don't restore %rax in here and just + * call ret. + */ + "retq\n" + ".global uretprobe_trampoline_end\n" + "uretprobe_trampoline_end:\n" + ".popsection\n" +); + +extern u8 uretprobe_trampoline_entry[]; +extern u8 uretprobe_trampoline_end[]; +extern u8 uretprobe_syscall_check[]; + +void *arch_uprobe_trampoline(unsigned long *psize) +{ + static uprobe_opcode_t insn = UPROBE_SWBP_INSN; + struct pt_regs *regs = task_pt_regs(current); + + /* + * At the moment the uretprobe syscall trampoline is supported + * only for native 64-bit process, the compat process still uses + * standard breakpoint. + */ + if (user_64bit_mode(regs)) { + *psize = uretprobe_trampoline_end - uretprobe_trampoline_entry; + return uretprobe_trampoline_entry; + } + + *psize = UPROBE_SWBP_INSN_SIZE; + return &insn; +} + +static unsigned long trampoline_check_ip(void) +{ + unsigned long tramp = uprobe_get_trampoline_vaddr(); + + return tramp + (uretprobe_syscall_check - uretprobe_trampoline_entry); +} + +SYSCALL_DEFINE0(uretprobe) +{ + struct pt_regs *regs = task_pt_regs(current); + unsigned long err, ip, sp, r11_cx_ax[3]; + + if (regs->ip != trampoline_check_ip()) + goto sigill; + + err = copy_from_user(r11_cx_ax, (void __user *)regs->sp, sizeof(r11_cx_ax)); + if (err) + goto sigill; + + /* expose the "right" values of r11/cx/ax/sp to uprobe_consumer/s */ + regs->r11 = r11_cx_ax[0]; + regs->cx = r11_cx_ax[1]; + regs->ax = r11_cx_ax[2]; + regs->sp += sizeof(r11_cx_ax); + regs->orig_ax = -1; + + ip = regs->ip; + sp = regs->sp; + + uprobe_handle_trampoline(regs); + + /* + * Some of the uprobe consumers has changed sp, we can do nothing, + * just return via iret. + * .. or shadow stack is enabled, in which case we need to skip + * return through the user space stack address. + */ + if (regs->sp != sp || shstk_is_enabled()) + return regs->ax; + regs->sp -= sizeof(r11_cx_ax); + + /* for the case uprobe_consumer has changed r11/cx */ + r11_cx_ax[0] = regs->r11; + r11_cx_ax[1] = regs->cx; + + /* + * ax register is passed through as return value, so we can use + * its space on stack for ip value and jump to it through the + * trampoline's ret instruction + */ + r11_cx_ax[2] = regs->ip; + regs->ip = ip; + + err = copy_to_user((void __user *)regs->sp, r11_cx_ax, sizeof(r11_cx_ax)); + if (err) + goto sigill; + + /* ensure sysret, see do_syscall_64() */ + regs->r11 = regs->flags; + regs->cx = regs->ip; + + return regs->ax; + +sigill: + force_sig(SIGILL); + return -1; +} + /* * If arch_uprobe->insn doesn't use rip-relative addressing, return * immediately. Otherwise, rewrite the instruction so that it accesses diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h index f46e0ca0169c..b503fafb7fb3 100644 --- a/include/linux/uprobes.h +++ b/include/linux/uprobes.h @@ -138,6 +138,9 @@ extern bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check c extern bool arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs); extern void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr, void *src, unsigned long len); +extern void uprobe_handle_trampoline(struct pt_regs *regs); +extern void *arch_uprobe_trampoline(unsigned long *psize); +extern unsigned long uprobe_get_trampoline_vaddr(void); #else /* !CONFIG_UPROBES */ struct uprobes_state { }; diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 2c83ba776fc7..2816e65729ac 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1474,11 +1474,20 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area) return ret; } +void * __weak arch_uprobe_trampoline(unsigned long *psize) +{ + static uprobe_opcode_t insn = UPROBE_SWBP_INSN; + + *psize = UPROBE_SWBP_INSN_SIZE; + return &insn; +} + static struct xol_area *__create_xol_area(unsigned long vaddr) { struct mm_struct *mm = current->mm; - uprobe_opcode_t insn = UPROBE_SWBP_INSN; + unsigned long insns_size; struct xol_area *area; + void *insns; area = kmalloc(sizeof(*area), GFP_KERNEL); if (unlikely(!area)) @@ -1502,7 +1511,8 @@ static struct xol_area *__create_xol_area(unsigned long vaddr) /* Reserve the 1st slot for get_trampoline_vaddr() */ set_bit(0, area->bitmap); atomic_set(&area->slot_count, 1); - arch_uprobe_copy_ixol(area->pages[0], 0, &insn, UPROBE_SWBP_INSN_SIZE); + insns = arch_uprobe_trampoline(&insns_size); + arch_uprobe_copy_ixol(area->pages[0], 0, insns, insns_size); if (!xol_add_vma(mm, area)) return area; @@ -1827,7 +1837,7 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags) * * Returns -1 in case the xol_area is not allocated. */ -static unsigned long get_trampoline_vaddr(void) +unsigned long uprobe_get_trampoline_vaddr(void) { struct xol_area *area; unsigned long trampoline_vaddr = -1; @@ -1878,7 +1888,7 @@ static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs) if (!ri) return; - trampoline_vaddr = get_trampoline_vaddr(); + trampoline_vaddr = uprobe_get_trampoline_vaddr(); orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs); if (orig_ret_vaddr == -1) goto fail; @@ -2123,7 +2133,7 @@ static struct return_instance *find_next_ret_chain(struct return_instance *ri) return ri; } -static void handle_trampoline(struct pt_regs *regs) +void uprobe_handle_trampoline(struct pt_regs *regs) { struct uprobe_task *utask; struct return_instance *ri, *next; @@ -2187,8 +2197,8 @@ static void handle_swbp(struct pt_regs *regs) int is_swbp; bp_vaddr = uprobe_get_swbp_addr(regs); - if (bp_vaddr == get_trampoline_vaddr()) - return handle_trampoline(regs); + if (bp_vaddr == uprobe_get_trampoline_vaddr()) + return uprobe_handle_trampoline(regs); uprobe = find_active_uprobe(bp_vaddr, &is_swbp); if (!uprobe) { |