From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- arch/x86/kernel/unwind_frame.c | 419 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 419 insertions(+) create mode 100644 arch/x86/kernel/unwind_frame.c (limited to 'arch/x86/kernel/unwind_frame.c') diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c new file mode 100644 index 000000000..d8ba93778 --- /dev/null +++ b/arch/x86/kernel/unwind_frame.c @@ -0,0 +1,419 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define FRAME_HEADER_SIZE (sizeof(long) * 2) + +unsigned long unwind_get_return_address(struct unwind_state *state) +{ + if (unwind_done(state)) + return 0; + + return __kernel_text_address(state->ip) ? state->ip : 0; +} +EXPORT_SYMBOL_GPL(unwind_get_return_address); + +unsigned long *unwind_get_return_address_ptr(struct unwind_state *state) +{ + if (unwind_done(state)) + return NULL; + + return state->regs ? &state->regs->ip : state->bp + 1; +} + +static void unwind_dump(struct unwind_state *state) +{ + static bool dumped_before = false; + bool prev_zero, zero = false; + unsigned long word, *sp; + struct stack_info stack_info = {0}; + unsigned long visit_mask = 0; + + if (dumped_before) + return; + + dumped_before = true; + + printk_deferred("unwind stack type:%d next_sp:%p mask:0x%lx graph_idx:%d\n", + state->stack_info.type, state->stack_info.next_sp, + state->stack_mask, state->graph_idx); + + for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp; + sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { + if (get_stack_info(sp, state->task, &stack_info, &visit_mask)) + break; + + for (; sp < stack_info.end; sp++) { + + word = READ_ONCE_NOCHECK(*sp); + + prev_zero = zero; + zero = word == 0; + + if (zero) { + if (!prev_zero) + printk_deferred("%p: %0*x ...\n", + sp, BITS_PER_LONG/4, 0); + continue; + } + + printk_deferred("%p: %0*lx (%pB)\n", + sp, BITS_PER_LONG/4, word, (void *)word); + } + } +} + +static bool in_entry_code(unsigned long ip) +{ + char *addr = (char *)ip; + + return addr >= __entry_text_start && addr < __entry_text_end; +} + +static inline unsigned long *last_frame(struct unwind_state *state) +{ + return (unsigned long *)task_pt_regs(state->task) - 2; +} + +static bool is_last_frame(struct unwind_state *state) +{ + return state->bp == last_frame(state); +} + +#ifdef CONFIG_X86_32 +#define GCC_REALIGN_WORDS 3 +#else +#define GCC_REALIGN_WORDS 1 +#endif + +static inline unsigned long *last_aligned_frame(struct unwind_state *state) +{ + return last_frame(state) - GCC_REALIGN_WORDS; +} + +static bool is_last_aligned_frame(struct unwind_state *state) +{ + unsigned long *last_bp = last_frame(state); + unsigned long *aligned_bp = last_aligned_frame(state); + + /* + * GCC can occasionally decide to realign the stack pointer and change + * the offset of the stack frame in the prologue of a function called + * by head/entry code. Examples: + * + * : + * push %edi + * lea 0x8(%esp),%edi + * and $0xfffffff8,%esp + * pushl -0x4(%edi) + * push %ebp + * mov %esp,%ebp + * + * : + * lea 0x8(%rsp),%r10 + * and $0xfffffffffffffff0,%rsp + * pushq -0x8(%r10) + * push %rbp + * mov %rsp,%rbp + * + * After aligning the stack, it pushes a duplicate copy of the return + * address before pushing the frame pointer. + */ + return (state->bp == aligned_bp && *(aligned_bp + 1) == *(last_bp + 1)); +} + +static bool is_last_ftrace_frame(struct unwind_state *state) +{ + unsigned long *last_bp = last_frame(state); + unsigned long *last_ftrace_bp = last_bp - 3; + + /* + * When unwinding from an ftrace handler of a function called by entry + * code, the stack layout of the last frame is: + * + * bp + * parent ret addr + * bp + * function ret addr + * parent ret addr + * pt_regs + * ----------------- + */ + return (state->bp == last_ftrace_bp && + *state->bp == *(state->bp + 2) && + *(state->bp + 1) == *(state->bp + 4)); +} + +static bool is_last_task_frame(struct unwind_state *state) +{ + return is_last_frame(state) || is_last_aligned_frame(state) || + is_last_ftrace_frame(state); +} + +/* + * This determines if the frame pointer actually contains an encoded pointer to + * pt_regs on the stack. See ENCODE_FRAME_POINTER. + */ +#ifdef CONFIG_X86_64 +static struct pt_regs *decode_frame_pointer(unsigned long *bp) +{ + unsigned long regs = (unsigned long)bp; + + if (!(regs & 0x1)) + return NULL; + + return (struct pt_regs *)(regs & ~0x1); +} +#else +static struct pt_regs *decode_frame_pointer(unsigned long *bp) +{ + unsigned long regs = (unsigned long)bp; + + if (regs & 0x80000000) + return NULL; + + return (struct pt_regs *)(regs | 0x80000000); +} +#endif + +/* + * While walking the stack, KMSAN may stomp on stale locals from other + * functions that were marked as uninitialized upon function exit, and + * now hold the call frame information for the current function (e.g. the frame + * pointer). Because KMSAN does not specifically mark call frames as + * initialized, false positive reports are possible. To prevent such reports, + * we mark the functions scanning the stack (here and below) with + * __no_kmsan_checks. + */ +__no_kmsan_checks +static bool update_stack_state(struct unwind_state *state, + unsigned long *next_bp) +{ + struct stack_info *info = &state->stack_info; + enum stack_type prev_type = info->type; + struct pt_regs *regs; + unsigned long *frame, *prev_frame_end, *addr_p, addr; + size_t len; + + if (state->regs) + prev_frame_end = (void *)state->regs + sizeof(*state->regs); + else + prev_frame_end = (void *)state->bp + FRAME_HEADER_SIZE; + + /* Is the next frame pointer an encoded pointer to pt_regs? */ + regs = decode_frame_pointer(next_bp); + if (regs) { + frame = (unsigned long *)regs; + len = sizeof(*regs); + state->got_irq = true; + } else { + frame = next_bp; + len = FRAME_HEADER_SIZE; + } + + /* + * If the next bp isn't on the current stack, switch to the next one. + * + * We may have to traverse multiple stacks to deal with the possibility + * that info->next_sp could point to an empty stack and the next bp + * could be on a subsequent stack. + */ + while (!on_stack(info, frame, len)) + if (get_stack_info(info->next_sp, state->task, info, + &state->stack_mask)) + return false; + + /* Make sure it only unwinds up and doesn't overlap the prev frame: */ + if (state->orig_sp && state->stack_info.type == prev_type && + frame < prev_frame_end) + return false; + + /* Move state to the next frame: */ + if (regs) { + state->regs = regs; + state->bp = NULL; + } else { + state->bp = next_bp; + state->regs = NULL; + } + + /* Save the return address: */ + if (state->regs && user_mode(state->regs)) + state->ip = 0; + else { + addr_p = unwind_get_return_address_ptr(state); + addr = READ_ONCE_TASK_STACK(state->task, *addr_p); + state->ip = unwind_recover_ret_addr(state, addr, addr_p); + } + + /* Save the original stack pointer for unwind_dump(): */ + if (!state->orig_sp) + state->orig_sp = frame; + + return true; +} + +__no_kmsan_checks +bool unwind_next_frame(struct unwind_state *state) +{ + struct pt_regs *regs; + unsigned long *next_bp; + + if (unwind_done(state)) + return false; + + /* Have we reached the end? */ + if (state->regs && user_mode(state->regs)) + goto the_end; + + if (is_last_task_frame(state)) { + regs = task_pt_regs(state->task); + + /* + * kthreads (other than the boot CPU's idle thread) have some + * partial regs at the end of their stack which were placed + * there by copy_thread(). But the regs don't have any + * useful information, so we can skip them. + * + * This user_mode() check is slightly broader than a PF_KTHREAD + * check because it also catches the awkward situation where a + * newly forked kthread transitions into a user task by calling + * kernel_execve(), which eventually clears PF_KTHREAD. + */ + if (!user_mode(regs)) + goto the_end; + + /* + * We're almost at the end, but not quite: there's still the + * syscall regs frame. Entry code doesn't encode the regs + * pointer for syscalls, so we have to set it manually. + */ + state->regs = regs; + state->bp = NULL; + state->ip = 0; + return true; + } + + /* Get the next frame pointer: */ + if (state->next_bp) { + next_bp = state->next_bp; + state->next_bp = NULL; + } else if (state->regs) { + next_bp = (unsigned long *)state->regs->bp; + } else { + next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp); + } + + /* Move to the next frame if it's safe: */ + if (!update_stack_state(state, next_bp)) + goto bad_address; + + return true; + +bad_address: + state->error = true; + + /* + * When unwinding a non-current task, the task might actually be + * running on another CPU, in which case it could be modifying its + * stack while we're reading it. This is generally not a problem and + * can be ignored as long as the caller understands that unwinding + * another task will not always succeed. + */ + if (state->task != current) + goto the_end; + + /* + * Don't warn if the unwinder got lost due to an interrupt in entry + * code or in the C handler before the first frame pointer got set up: + */ + if (state->got_irq && in_entry_code(state->ip)) + goto the_end; + if (state->regs && + state->regs->sp >= (unsigned long)last_aligned_frame(state) && + state->regs->sp < (unsigned long)task_pt_regs(state->task)) + goto the_end; + + /* + * There are some known frame pointer issues on 32-bit. Disable + * unwinder warnings on 32-bit until it gets objtool support. + */ + if (IS_ENABLED(CONFIG_X86_32)) + goto the_end; + + if (state->task != current) + goto the_end; + + if (state->regs) { + printk_deferred_once(KERN_WARNING + "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n", + state->regs, state->task->comm, + state->task->pid, next_bp); + unwind_dump(state); + } else { + printk_deferred_once(KERN_WARNING + "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n", + state->bp, state->task->comm, + state->task->pid, next_bp); + unwind_dump(state); + } +the_end: + state->stack_info.type = STACK_TYPE_UNKNOWN; + return false; +} +EXPORT_SYMBOL_GPL(unwind_next_frame); + +void __unwind_start(struct unwind_state *state, struct task_struct *task, + struct pt_regs *regs, unsigned long *first_frame) +{ + unsigned long *bp; + + memset(state, 0, sizeof(*state)); + state->task = task; + state->got_irq = (regs); + + /* Don't even attempt to start from user mode regs: */ + if (regs && user_mode(regs)) { + state->stack_info.type = STACK_TYPE_UNKNOWN; + return; + } + + bp = get_frame_pointer(task, regs); + + /* + * If we crash with IP==0, the last successfully executed instruction + * was probably an indirect function call with a NULL function pointer. + * That means that SP points into the middle of an incomplete frame: + * *SP is a return pointer, and *(SP-sizeof(unsigned long)) is where we + * would have written a frame pointer if we hadn't crashed. + * Pretend that the frame is complete and that BP points to it, but save + * the real BP so that we can use it when looking for the next frame. + */ + if (regs && regs->ip == 0 && (unsigned long *)regs->sp >= first_frame) { + state->next_bp = bp; + bp = ((unsigned long *)regs->sp) - 1; + } + + /* Initialize stack info and make sure the frame data is accessible: */ + get_stack_info(bp, state->task, &state->stack_info, + &state->stack_mask); + update_stack_state(state, bp); + + /* + * The caller can provide the address of the first frame directly + * (first_frame) or indirectly (regs->sp) to indicate which stack frame + * to start unwinding at. Skip ahead until we reach it. + */ + while (!unwind_done(state) && + (!on_stack(&state->stack_info, first_frame, sizeof(long)) || + (state->next_bp == NULL && state->bp < first_frame))) + unwind_next_frame(state); +} +EXPORT_SYMBOL_GPL(__unwind_start); -- cgit v1.2.3