kernel/debug/kdb/kdb_support.c

/*
 * Kernel Debugger Architecture Independent Support Functions
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 1999-2004 Silicon Graphics, Inc.  All Rights Reserved.
 * Copyright (c) 2009 Wind River Systems, Inc.  All Rights Reserved.
 * 03/02/13    added new 2.5 kallsyms <xavier.bru@bull.net>
 */

#include <linux/types.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/kallsyms.h>
#include <linux/stddef.h>
#include <linux/vmalloc.h>
#include <linux/ptrace.h>
#include <linux/module.h>
#include <linux/highmem.h>
#include <linux/hardirq.h>
#include <linux/delay.h>
#include <linux/uaccess.h>
#include <linux/kdb.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include "kdb_private.h"

/*
 * kdbgetsymval - Return the address of the given symbol.
 *
 * Parameters:
 *	symname	Character string containing symbol name
 *      symtab  Structure to receive results
 * Returns:
 *	0	Symbol not found, symtab zero filled
 *	1	Symbol mapped to module/symbol/section, data in symtab
 */
int kdbgetsymval(const char *symname, kdb_symtab_t *symtab)
{
	kdb_dbg_printf(AR, "symname=%s, symtab=%px\n", symname, symtab);
	memset(symtab, 0, sizeof(*symtab));
	symtab->sym_start = kallsyms_lookup_name(symname);
	if (symtab->sym_start) {
		kdb_dbg_printf(AR, "returns 1, symtab->sym_start=0x%lx\n",
			       symtab->sym_start);
		return 1;
	}
	kdb_dbg_printf(AR, "returns 0\n");
	return 0;
}
EXPORT_SYMBOL(kdbgetsymval);

/**
 * kdbnearsym() - Return the name of the symbol with the nearest address
 *                less than @addr.
 * @addr: Address to check for near symbol
 * @symtab: Structure to receive results
 *
 * WARNING: This function may return a pointer to a single statically
 * allocated buffer (namebuf). kdb's unusual calling context (single
 * threaded, all other CPUs halted) provides us sufficient locking for
 * this to be safe. The only constraint imposed by the static buffer is
 * that the caller must consume any previous reply prior to another call
 * to lookup a new symbol.
 *
 * Note that, strictly speaking, some architectures may re-enter the kdb
 * trap if the system turns out to be very badly damaged and this breaks
 * the single-threaded assumption above. In these circumstances successful
 * continuation and exit from the inner trap is unlikely to work and any
 * user attempting this receives a prominent warning before being allowed
 * to progress. In these circumstances we remain memory safe because
 * namebuf[KSYM_NAME_LEN-1] will never change from '\0' although we do
 * tolerate the possibility of garbled symbol display from the outer kdb
 * trap.
 *
 * Return:
 * * 0 - No sections contain this address, symtab zero filled
 * * 1 - Address mapped to module/symbol/section, data in symtab
 */
int kdbnearsym(unsigned long addr, kdb_symtab_t *symtab)
{
	int ret = 0;
	unsigned long symbolsize = 0;
	unsigned long offset = 0;
	static char namebuf[KSYM_NAME_LEN];

	kdb_dbg_printf(AR, "addr=0x%lx, symtab=%px\n", addr, symtab);
	memset(symtab, 0, sizeof(*symtab));

	if (addr < 4096)
		goto out;

	symtab->sym_name = kallsyms_lookup(addr, &symbolsize , &offset,
				(char **)(&symtab->mod_name), namebuf);
	if (offset > 8*1024*1024) {
		symtab->sym_name = NULL;
		addr = offset = symbolsize = 0;
	}
	symtab->sym_start = addr - offset;
	symtab->sym_end = symtab->sym_start + symbolsize;
	ret = symtab->sym_name != NULL && *(symtab->sym_name) != '\0';

	if (symtab->mod_name == NULL)
		symtab->mod_name = "kernel";
	kdb_dbg_printf(AR, "returns %d symtab->sym_start=0x%lx, symtab->mod_name=%px, symtab->sym_name=%px (%s)\n",
		       ret, symtab->sym_start, symtab->mod_name, symtab->sym_name, symtab->sym_name);
out:
	return ret;
}

static char ks_namebuf[KSYM_NAME_LEN+1], ks_namebuf_prev[KSYM_NAME_LEN+1];

/*
 * kallsyms_symbol_complete
 *
 * Parameters:
 *	prefix_name	prefix of a symbol name to lookup
 *	max_len		maximum length that can be returned
 * Returns:
 *	Number of symbols which match the given prefix.
 * Notes:
 *	prefix_name is changed to contain the longest unique prefix that
 *	starts with this prefix (tab completion).
 */
int kallsyms_symbol_complete(char *prefix_name, int max_len)
{
	loff_t pos = 0;
	int prefix_len = strlen(prefix_name), prev_len = 0;
	int i, number = 0;
	const char *name;

	while ((name = kdb_walk_kallsyms(&pos))) {
		if (strncmp(name, prefix_name, prefix_len) == 0) {
			strscpy(ks_namebuf, name, sizeof(ks_namebuf));
			/* Work out the longest name that matches the prefix */
			if (++number == 1) {
				prev_len = min_t(int, max_len-1,
						 strlen(ks_namebuf));
				memcpy(ks_namebuf_prev, ks_namebuf, prev_len);
				ks_namebuf_prev[prev_len] = '\0';
				continue;
			}
			for (i = 0; i < prev_len; i++) {
				if (ks_namebuf[i] != ks_namebuf_prev[i]) {
					prev_len = i;
					ks_namebuf_prev[i] = '\0';
					break;
				}
			}
		}
	}
	if (prev_len > prefix_len)
		memcpy(prefix_name, ks_namebuf_prev, prev_len+1);
	return number;
}

/*
 * kallsyms_symbol_next
 *
 * Parameters:
 *	prefix_name	prefix of a symbol name to lookup
 *	flag	0 means search from the head, 1 means continue search.
 *	buf_size	maximum length that can be written to prefix_name
 *			buffer
 * Returns:
 *	1 if a symbol matches the given prefix.
 *	0 if no string found
 */
int kallsyms_symbol_next(char *prefix_name, int flag, int buf_size)
{
	int prefix_len = strlen(prefix_name);
	static loff_t pos;
	const char *name;

	if (!flag)
		pos = 0;

	while ((name = kdb_walk_kallsyms(&pos))) {
		if (!strncmp(name, prefix_name, prefix_len))
			return strscpy(prefix_name, name, buf_size);
	}
	return 0;
}

/*
 * kdb_symbol_print - Standard method for printing a symbol name and offset.
 * Inputs:
 *	addr	Address to be printed.
 *	symtab	Address of symbol data, if NULL this routine does its
 *		own lookup.
 *	punc	Punctuation for string, bit field.
 * Remarks:
 *	The string and its punctuation is only printed if the address
 *	is inside the kernel, except that the value is always printed
 *	when requested.
 */
void kdb_symbol_print(unsigned long addr, const kdb_symtab_t *symtab_p,
		      unsigned int punc)
{
	kdb_symtab_t symtab, *symtab_p2;
	if (symtab_p) {
		symtab_p2 = (kdb_symtab_t *)symtab_p;
	} else {
		symtab_p2 = &symtab;
		kdbnearsym(addr, symtab_p2);
	}
	if (!(symtab_p2->sym_name || (punc & KDB_SP_VALUE)))
		return;
	if (punc & KDB_SP_SPACEB)
		kdb_printf(" ");
	if (punc & KDB_SP_VALUE)
		kdb_printf(kdb_machreg_fmt0, addr);
	if (symtab_p2->sym_name) {
		if (punc & KDB_SP_VALUE)
			kdb_printf(" ");
		if (punc & KDB_SP_PAREN)
			kdb_printf("(");
		if (strcmp(symtab_p2->mod_name, "kernel"))
			kdb_printf("[%s]", symtab_p2->mod_name);
		kdb_printf("%s", symtab_p2->sym_name);
		if (addr != symtab_p2->sym_start)
			kdb_printf("+0x%lx", addr - symtab_p2->sym_start);
		if (punc & KDB_SP_SYMSIZE)
			kdb_printf("/0x%lx",
				   symtab_p2->sym_end - symtab_p2->sym_start);
		if (punc & KDB_SP_PAREN)
			kdb_printf(")");
	}
	if (punc & KDB_SP_SPACEA)
		kdb_printf(" ");
	if (punc & KDB_SP_NEWLINE)
		kdb_printf("\n");
}

/*
 * kdb_strdup - kdb equivalent of strdup, for disasm code.
 * Inputs:
 *	str	The string to duplicate.
 *	type	Flags to kmalloc for the new string.
 * Returns:
 *	Address of the new string, NULL if storage could not be allocated.
 * Remarks:
 *	This is not in lib/string.c because it uses kmalloc which is not
 *	available when string.o is used in boot loaders.
 */
char *kdb_strdup(const char *str, gfp_t type)
{
	int n = strlen(str)+1;
	char *s = kmalloc(n, type);
	if (!s)
		return NULL;
	return strcpy(s, str);
}

/*
 * kdb_getarea_size - Read an area of data.  The kdb equivalent of
 *	copy_from_user, with kdb messages for invalid addresses.
 * Inputs:
 *	res	Pointer to the area to receive the result.
 *	addr	Address of the area to copy.
 *	size	Size of the area.
 * Returns:
 *	0 for success, < 0 for error.
 */
int kdb_getarea_size(void *res, unsigned long addr, size_t size)
{
	int ret = copy_from_kernel_nofault((char *)res, (char *)addr, size);
	if (ret) {
		if (!KDB_STATE(SUPPRESS)) {
			kdb_func_printf("Bad address 0x%lx\n", addr);
			KDB_STATE_SET(SUPPRESS);
		}
		ret = KDB_BADADDR;
	} else {
		KDB_STATE_CLEAR(SUPPRESS);
	}
	return ret;
}

/*
 * kdb_putarea_size - Write an area of data.  The kdb equivalent of
 *	copy_to_user, with kdb messages for invalid addresses.
 * Inputs:
 *	addr	Address of the area to write to.
 *	res	Pointer to the area holding the data.
 *	size	Size of the area.
 * Returns:
 *	0 for success, < 0 for error.
 */
int kdb_putarea_size(unsigned long addr, void *res, size_t size)
{
	int ret = copy_to_kernel_nofault((char *)addr, (char *)res, size);
	if (ret) {
		if (!KDB_STATE(SUPPRESS)) {
			kdb_func_printf("Bad address 0x%lx\n", addr);
			KDB_STATE_SET(SUPPRESS);
		}
		ret = KDB_BADADDR;
	} else {
		KDB_STATE_CLEAR(SUPPRESS);
	}
	return ret;
}

/*
 * kdb_getphys - Read data from a physical address. Validate the
 * 	address is in range, use kmap_atomic() to get data
 * 	similar to kdb_getarea() - but for phys addresses
 * Inputs:
 * 	res	Pointer to the word to receive the result
 * 	addr	Physical address of the area to copy
 * 	size	Size of the area
 * Returns:
 *	0 for success, < 0 for error.
 */
static int kdb_getphys(void *res, unsigned long addr, size_t size)
{
	unsigned long pfn;
	void *vaddr;
	struct page *page;

	pfn = (addr >> PAGE_SHIFT);
	if (!pfn_valid(pfn))
		return 1;
	page = pfn_to_page(pfn);
	vaddr = kmap_atomic(page);
	memcpy(res, vaddr + (addr & (PAGE_SIZE - 1)), size);
	kunmap_atomic(vaddr);

	return 0;
}

/*
 * kdb_getphysword
 * Inputs:
 *	word	Pointer to the word to receive the result.
 *	addr	Address of the area to copy.
 *	size	Size of the area.
 * Returns:
 *	0 for success, < 0 for error.
 */
int kdb_getphysword(unsigned long *word, unsigned long addr, size_t size)
{
	int diag;
	__u8  w1;
	__u16 w2;
	__u32 w4;
	__u64 w8;
	*word = 0;	/* Default value if addr or size is invalid */

	switch (size) {
	case 1:
		diag = kdb_getphys(&w1, addr, sizeof(w1));
		if (!diag)
			*word = w1;
		break;
	case 2:
		diag = kdb_getphys(&w2, addr, sizeof(w2));
		if (!diag)
			*word = w2;
		break;
	case 4:
		diag = kdb_getphys(&w4, addr, sizeof(w4));
		if (!diag)
			*word = w4;
		break;
	case 8:
		if (size <= sizeof(*word)) {
			diag = kdb_getphys(&w8, addr, sizeof(w8));
			if (!diag)
				*word = w8;
			break;
		}
		fallthrough;
	default:
		diag = KDB_BADWIDTH;
		kdb_func_printf("bad width %zu\n", size);
	}
	return diag;
}

/*
 * kdb_getword - Read a binary value.  Unlike kdb_getarea, this treats
 *	data as numbers.
 * Inputs:
 *	word	Pointer to the word to receive the result.
 *	addr	Address of the area to copy.
 *	size	Size of the area.
 * Returns:
 *	0 for success, < 0 for error.
 */
int kdb_getword(unsigned long *word, unsigned long addr, size_t size)
{
	int diag;
	__u8  w1;
	__u16 w2;
	__u32 w4;
	__u64 w8;
	*word = 0;	/* Default value if addr or size is invalid */
	switch (size) {
	case 1:
		diag = kdb_getarea(w1, addr);
		if (!diag)
			*word = w1;
		break;
	case 2:
		diag = kdb_getarea(w2, addr);
		if (!diag)
			*word = w2;
		break;
	case 4:
		diag = kdb_getarea(w4, addr);
		if (!diag)
			*word = w4;
		break;
	case 8:
		if (size <= sizeof(*word)) {
			diag = kdb_getarea(w8, addr);
			if (!diag)
				*word = w8;
			break;
		}
		fallthrough;
	default:
		diag = KDB_BADWIDTH;
		kdb_func_printf("bad width %zu\n", size);
	}
	return diag;
}

/*
 * kdb_putword - Write a binary value.  Unlike kdb_putarea, this
 *	treats data as numbers.
 * Inputs:
 *	addr	Address of the area to write to..
 *	word	The value to set.
 *	size	Size of the area.
 * Returns:
 *	0 for success, < 0 for error.
 */
int kdb_putword(unsigned long addr, unsigned long word, size_t size)
{
	int diag;
	__u8  w1;
	__u16 w2;
	__u32 w4;
	__u64 w8;
	switch (size) {
	case 1:
		w1 = word;
		diag = kdb_putarea(addr, w1);
		break;
	case 2:
		w2 = word;
		diag = kdb_putarea(addr, w2);
		break;
	case 4:
		w4 = word;
		diag = kdb_putarea(addr, w4);
		break;
	case 8:
		if (size <= sizeof(word)) {
			w8 = word;
			diag = kdb_putarea(addr, w8);
			break;
		}
		fallthrough;
	default:
		diag = KDB_BADWIDTH;
		kdb_func_printf("bad width %zu\n", size);
	}
	return diag;
}



/*
 * kdb_task_state_char - Return the character that represents the task state.
 * Inputs:
 *	p	struct task for the process
 * Returns:
 *	One character to represent the task state.
 */
char kdb_task_state_char (const struct task_struct *p)
{
	unsigned long tmp;
	char state;
	int cpu;

	if (!p ||
	    copy_from_kernel_nofault(&tmp, (char *)p, sizeof(unsigned long)))
		return 'E';

	state = task_state_to_char((struct task_struct *) p);

	if (is_idle_task(p)) {
		/* Idle task.  Is it really idle, apart from the kdb
		 * interrupt? */
		cpu = kdb_process_cpu(p);
		if (!kdb_task_has_cpu(p) || kgdb_info[cpu].irq_depth == 1) {
			if (cpu != kdb_initial_cpu)
				state = '-';	/* idle task */
		}
	} else if (!p->mm && strchr("IMS", state)) {
		state = tolower(state);		/* sleeping system daemon */
	}
	return state;
}

/*
 * kdb_task_state - Return true if a process has the desired state
 *	given by the mask.
 * Inputs:
 *	p	struct task for the process
 *	mask	set of characters used to select processes; both NULL
 *	        and the empty string mean adopt a default filter, which
 *	        is to suppress sleeping system daemons and the idle tasks
 * Returns:
 *	True if the process matches at least one criteria defined by the mask.
 */
bool kdb_task_state(const struct task_struct *p, const char *mask)
{
	char state = kdb_task_state_char(p);

	/* If there is no mask, then we will filter code that runs when the
	 * scheduler is idling and any system daemons that are currently
	 * sleeping.
	 */
	if (!mask || mask[0] == '\0')
		return !strchr("-ims", state);

	/* A is a special case that matches all states */
	if (strchr(mask, 'A'))
		return true;

	return strchr(mask, state);
}

/* Maintain a small stack of kdb_flags to allow recursion without disturbing
 * the global kdb state.
 */

static int kdb_flags_stack[4], kdb_flags_index;

void kdb_save_flags(void)
{
	BUG_ON(kdb_flags_index >= ARRAY_SIZE(kdb_flags_stack));
	kdb_flags_stack[kdb_flags_index++] = kdb_flags;
}

void kdb_restore_flags(void)
{
	BUG_ON(kdb_flags_index <= 0);
	kdb_flags = kdb_flags_stack[--kdb_flags_index];
}