// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2009 Matt Fleming <matt@console-pimps.org>
*
* This is an implementation of a DWARF unwinder. Its main purpose is
* for generating stacktrace information. Based on the DWARF 3
* specification from http://www.dwarfstd.org.
*
* TODO:
* - DWARF64 doesn't work.
* - Registers with DWARF_VAL_OFFSET rules aren't handled properly.
*/
/* #define DEBUG */
#include <linux/kernel.h>
#include <linux/io.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/mm.h>
#include <linux/elf.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/dwarf.h>
#include <asm/unwinder.h>
#include <asm/sections.h>
#include <asm/unaligned.h>
#include <asm/stacktrace.h>
/* Reserve enough memory for two stack frames */
#define DWARF_FRAME_MIN_REQ 2
/* ... with 4 registers per frame. */
#define DWARF_REG_MIN_REQ (DWARF_FRAME_MIN_REQ * 4)
static struct kmem_cache *dwarf_frame_cachep;
static mempool_t *dwarf_frame_pool;
static struct kmem_cache *dwarf_reg_cachep;
static mempool_t *dwarf_reg_pool;
static struct rb_root cie_root;
static DEFINE_SPINLOCK(dwarf_cie_lock);
static struct rb_root fde_root;
static DEFINE_SPINLOCK(dwarf_fde_lock);
static struct dwarf_cie *cached_cie;
static unsigned int dwarf_unwinder_ready;
/**
* dwarf_frame_alloc_reg - allocate memory for a DWARF register
* @frame: the DWARF frame whose list of registers we insert on
* @reg_num: the register number
*
* Allocate space for, and initialise, a dwarf reg from
* dwarf_reg_pool and insert it onto the (unsorted) linked-list of
* dwarf registers for @frame.
*
* Return the initialised DWARF reg.
*/
static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame,
unsigned int reg_num)
{
struct dwarf_reg *reg;
reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC);
if (!reg) {
printk(KERN_WARNING "Unable to allocate a DWARF register\n");
/*
* Let's just bomb hard here, we have no way to
* gracefully recover.
*/
UNWINDER_BUG();
}
reg->number = reg_num;
reg->addr = 0;
reg->flags = 0;
list_add(®->link, &frame->reg_list);
return reg;
}
static void dwarf_frame_free_regs(struct dwarf_frame *frame)
{
struct dwarf_reg *reg, *n;
list_for_each_entry_safe(reg, n, &frame->reg_list, link) {
list_del(®->link);
mempool_free(reg, dwarf_reg_pool);
}
}
/**
* dwarf_frame_reg - return a DWARF register
* @frame: the DWARF frame to search in for @reg_num
* @reg_num: the register number to search for
*
* Lookup and return the dwarf reg @reg_num for this frame. Return
* NULL if @reg_num is an register invalid number.
*/
static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame,
unsigned int reg_num)
{
struct dwarf_reg *reg;
list_for_each_entry(reg, &frame->reg_list, link) {
if (reg->number == reg_num)
return reg;
}
return NULL;
}
/**
* dwarf_read_addr - read dwarf data
* @src: source address of data
* @dst: destination address to store the data to
*
* Read 'n' bytes from @src, where 'n' is the size of an address on
* the native machine. We return the number of bytes read, which
* should always be 'n'. We also have to be careful when reading
* from @src and writing to @dst, because they can be arbitrarily
* aligned. Return 'n' - the number of bytes read.
*/
static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst)
{
u32 val = get_unaligned(src);
put_unaligned(val, dst);
return sizeof(unsigned long *);
}
/**
* dwarf_read_uleb128 - read unsigned LEB128 data
* @addr: the address where the ULEB128 data is stored
* @ret: address to store the result
*
* Decode an unsigned LEB128 encoded datum. The algorithm is taken
* from Appendix C of the DWARF 3 spec. For information on the
* encodings refer to section "7.6 - Variable Length Data". Return
* the number of bytes read.
*/
static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret)
{
unsigned int result;
unsigned char byte;
int shift, count;
result = 0;
shift = 0;
count = 0;
while (1) {
byte = __raw_readb(addr);
addr++;
count++;
result |= (byte & 0x7f) << shift;
shift += 7;
if (!(byte & 0x80))
break;
}
*ret = result;
return count;
}
/**
* dwarf_read_leb128 - read signed LEB128 data
* @addr: the address of the LEB128 encoded data
* @ret: address to store the result
*
* Decode signed LEB128 data. The algorithm is taken from Appendix
* C of the DWARF 3 spec. Return the number of bytes read.
*/
static inline unsigned long dwarf_read_leb128(char *addr, int *ret)
{
unsigned char byte;
int result, shift;
int num_bits;
int count;
result = 0;
shift = 0;
count = 0;
while (1) {
byte = __raw_readb(addr);
addr++;
result |= (byte & 0x7f) << shift;
shift += 7;
count++;
if (!(byte & 0x80))
break;
}
/* The number of bits in a signed integer. */
num_bits = 8 * sizeof(result);
if ((shift < num_bits) && (byte & 0x40))
result |= (-1 << shift);
*ret = result;
return count;
}
/**
* dwarf_read_encoded_value - return the decoded value at @addr
* @addr: the address of the encoded value
* @val: where to write the decoded value
* @encoding: the encoding with which we can decode @addr
*
* GCC emits encoded address in the .eh_frame FDE entries. Decode
* the value at @addr using @encoding. The decoded value is written
* to @val and the number of bytes read is returned.
*/
static int dwarf_read_encoded_value(char *addr, unsigned long *val,
char encoding)
{
unsigned long decoded_addr = 0;
int count = 0;
switch (encoding & 0x70) {
case DW_EH_PE_absptr:
break;
case DW_EH_PE_pcrel:
decoded_addr = (unsigned long)addr;
break;
default:
pr_debug("encoding=0x%x\n", (encoding & 0x70));
UNWINDER_BUG();
}
if ((encoding & 0x07) == 0x00)
encoding |= DW_EH_PE_udata4;
switch (encoding & 0x0f) {
case DW_EH_PE_sdata4:
case DW_EH_PE_udata4:
count += 4;
decoded_addr += get_unaligned((u32 *)addr);
__raw_writel(decoded_addr, val);
break;
default:
pr_debug("encoding=0x%x\n", encoding);
UNWINDER_BUG();
}
return count;
}
/**
* dwarf_entry_len - return the length of an FDE or CIE
* @addr: the address of the entry
* @len: the length of the entry
*
* Read the initial_length field of the entry and store the size of
* the entry in @len. We return the number of bytes read. Return a
* count of 0 on error.
*/
static inline int dwarf_entry_len(char *addr, unsigned long *len)
{
u32 initial_len;
int count;
initial_len = get_unaligned((u32 *)addr);
count = 4;
/*
* An initial length field value in the range DW_LEN_EXT_LO -
* DW_LEN_EXT_HI indicates an extension, and should not be
* interpreted as a length. The only extension that we currently
* understand is the use of DWARF64 addresses.
*/
if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) {
/*
* The 64-bit length field immediately follows the
* compulsory 32-bit length field.
*/
if (initial_len == DW_EXT_DWARF64) {
*len = get_unaligned((u64 *)addr + 4);
count = 12;
} else {
printk(KERN_WARNING "Unknown DWARF extension\n");
count = 0;
}
} else
*len = initial_len;
return count;
}
/**
* dwarf_lookup_cie - locate the cie
* @cie_ptr: pointer to help with lookup
*/
static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr)
{
struct rb_node **rb_node = &cie_root.rb_node;
struct dwarf_cie *cie = NULL;
unsigned long flags;
spin_lock_irqsave(&dwarf_cie_lock, flags);
/*
* We've cached the last CIE we looked up because chances are
* that the FDE wants this CIE.
*/
if (cached_cie && cached_cie->cie_pointer == cie_ptr) {
cie = cached_cie;
goto out;
}
while (*rb_node) {
struct dwarf_cie *cie_tmp;
cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
BUG_ON(!cie_tmp);
if (cie_ptr == cie_tmp->cie_pointer) {
cie = cie_tmp;
cached_cie = cie_tmp;
goto out;
} else {
if (cie_ptr < cie_tmp->cie_pointer)
rb_node = &(*rb_node)->rb_left;
else
rb_node = &(*rb_node)->rb_right;
}
}
out:
spin_unlock_irqrestore(&dwarf_cie_lock, flags);
return cie;
}
/**
* dwarf_lookup_fde - locate the FDE that covers pc
* @pc: the program counter
*/
struct dwarf_fde *dwarf_lookup_fde(unsigned long pc)
{
struct rb_node **rb_node = &fde_root.rb_node;
struct dwarf_fde *fde = NULL;
unsigned long flags;
spin_lock_irqsave(&dwarf_fde_lock, flags);
while (*rb_node) {
struct dwarf_fde *fde_tmp;
unsigned long tmp_start, tmp_end;
fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
BUG_ON(!fde_tmp);
tmp_start = fde_tmp->initial_location;
tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
if (pc < tmp_start) {
rb_node = &(*rb_node)->rb_left;
} else {
if (pc < tmp_end) {
fde = fde_tmp;
goto out;
} else
rb_node = &(*rb_node)->rb_right;
}
}
out:
spin_unlock_irqrestore(&dwarf_fde_lock, flags);
return fde;
}
/**
* dwarf_cfa_execute_insns - execute instructions to calculate a CFA
* @insn_start: address of the first instruction
* @insn_end: address of the last instruction
* @cie: the CIE for this function
* @fde: the FDE for this function
* @frame: the instructions calculate the CFA for this frame
* @pc: the program counter of the address we're interested in
*
* Execute the Call Frame instruction sequence starting at
* @insn_start and ending at @insn_end. The instructions describe
* how to calculate the Canonical Frame Address of a stackframe.
* Store the results in @frame.
*/
static int dwarf_cfa_execute_insns(unsigned char *insn_start,
unsigned char *insn_end,
struct dwarf_cie *cie,
struct dwarf_fde *fde,
struct dwarf_frame *frame,
unsigned long pc)
{
unsigned char insn;
unsigned char *current_insn;
unsigned int count, delta, reg, expr_len, offset;
struct dwarf_reg *regp;
current_insn = insn_start;
while (current_insn < insn_end && frame->pc <= pc) {
insn = __raw_readb(current_insn++);
/*
* Firstly, handle the opcodes that embed their operands
* in the instructions.
*/
switch (DW_CFA_opcode(insn)) {
case DW_CFA_advance_loc:
delta = DW_CFA_operand(insn);
delta *= cie->code_alignment_factor;
frame->pc += delta;
continue;
/* NOTREACHED */
case DW_CFA_offset:
reg = DW_CFA_operand(insn);
count = dwarf_read_uleb128(current_insn, &offset);
current_insn += count;
offset *= cie->data_alignment_factor;
regp = dwarf_frame_alloc_reg(frame, reg);
regp->addr = offset;
regp->flags |= DWARF_REG_OFFSET;
continue;
/* NOTREACHED */
case DW_CFA_restore:
reg = DW_CFA_operand(insn);
continue;
/* NOTREACHED */
}
/*
* Secondly, handle the opcodes that don't embed their
* operands in the instruction.
*/
switch (insn) {
case DW_CFA_nop:
continue;
case DW_CFA_advance_loc1:
delta = *current_insn++;
frame->pc += delta * cie->code_alignment_factor;
break;
case DW_CFA_advance_loc2:
delta = get_unaligned((u16 *)current_insn);
current_insn += 2;
frame->pc += delta * cie->code_alignment_factor;
break;
case DW_CFA_advance_loc4:
delta = get_unaligned((u32 *)current_insn);
current_insn += 4;
frame->pc += delta * cie->code_alignment_factor;
break;
case DW_CFA_offset_extended:
count = dwarf_read_uleb128(current_insn, ®);
current_insn += count;
count = dwarf_read_uleb128(current_insn, &offset);
current_insn += count;
offset *= cie->data_alignment_factor;
break;
case DW_CFA_restore_extended:
count = dwarf_read_uleb128(current_insn, ®);
current_insn += count;
break;
case DW_CFA_undefined:
count = dwarf_read_uleb128(current_insn, ®);
current_insn += count;
regp = dwarf_frame_alloc_reg(frame, reg);
regp->flags |= DWARF_UNDEFINED;
break;
case DW_CFA_def_cfa:
count = dwarf_read_uleb128(current_insn,
&frame->cfa_register);
current_insn += count;
count = dwarf_read_uleb128(current_insn,
&frame->cfa_offset);
current_insn += count;
frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
break;
case DW_CFA_def_cfa_register:
count = dwarf_read_uleb128(current_insn,
&frame->cfa_register);
current_insn += count;
frame->flags |= DWARF_FRAME_CFA_REG_OFFSET;
break;
case DW_CFA_def_cfa_offset:
count = dwarf_read_uleb128(current_insn, &offset);
current_insn += count;
frame->cfa_offset = offset;
break;
case DW_CFA_def_cfa_expression:
count = dwarf_read_uleb128(current_insn, &expr_len);
current_insn += count;
frame->cfa_expr = current_insn;
frame->cfa_expr_len = expr_len;
current_insn += expr_len;
frame->flags |= DWARF_FRAME_CFA_REG_EXP;
break;
case DW_CFA_offset_extended_sf:
count = dwarf_read_uleb128(current_insn, ®);
current_insn += count;
count = dwarf_read_leb128(current_insn, &offset);
current_insn += count;
offset *= cie->data_alignment_factor;
regp = dwarf_frame_alloc_reg(frame, reg);
regp->flags |= DWARF_REG_OFFSET;
regp->addr = offset;
break;
case DW_CFA_val_offset:
count = dwarf_read_uleb128(current_insn, ®);
current_insn += count;
count = dwarf_read_leb128(current_insn, &offset);
offset *= cie->data_alignment_factor;
regp = dwarf_frame_alloc_reg(frame, reg);
regp->flags |= DWARF_VAL_OFFSET;
regp->addr = offset;
break;
case DW_CFA_GNU_args_size:
count = dwarf_read_uleb128(current_insn, &offset);
current_insn += count;
break;
case DW_CFA_GNU_negative_offset_extended:
count = dwarf_read_uleb128(current_insn, ®);
current_insn += count;
count = dwarf_read_uleb128(current_insn, &offset);
offset *= cie->data_alignment_factor;
regp = dwarf_frame_alloc_reg(frame, reg);
regp->flags |= DWARF_REG_OFFSET;
regp->addr = -offset;
break;
default:
pr_debug("unhandled DWARF instruction 0x%x\n", insn);
UNWINDER_BUG();
break;
}
}
return 0;
}
/**
* dwarf_free_frame - free the memory allocated for @frame
* @frame: the frame to free
*/
void dwarf_free_frame(struct dwarf_frame *frame)
{
dwarf_frame_free_regs(frame);
mempool_free(frame, dwarf_frame_pool);
}
extern void ret_from_irq(void);
/**
* dwarf_unwind_stack - unwind the stack
*
* @pc: address of the function to unwind
* @prev: struct dwarf_frame of the previous stackframe on the callstack
*
* Return a struct dwarf_frame representing the most recent frame
* on the callstack. Each of the lower (older) stack frames are
* linked via the "prev" member.
*/
struct dwarf_frame *dwarf_unwind_stack(unsigned long pc,
struct dwarf_frame *prev)
{
struct dwarf_frame *frame;
struct dwarf_cie *cie;
struct dwarf_fde *fde;
struct dwarf_reg *reg;
unsigned long addr;
/*
* If we've been called in to before initialization has
* completed, bail out immediately.
*/
if (!dwarf_unwinder_ready)
return NULL;
/*
* If we're starting at the top of the stack we need get the
* contents of a physical register to get the CFA in order to
* begin the virtual unwinding of the stack.
*
* NOTE: the return address is guaranteed to be setup by the
* time this function makes its first function call.
*/
if (!pc || !prev)
pc = _THIS_IP_;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* If our stack has been patched by the function graph tracer
* then we might see the address of return_to_handler() where we
* expected to find the real return address.
*/
if (pc == (unsigned long)&return_to_handler) {
struct ftrace_ret_stack *ret_stack;
ret_stack = ftrace_graph_get_ret_stack(current, 0);
if (ret_stack)
pc = ret_stack->ret;
/*
* We currently have no way of tracking how many
* return_to_handler()'s we've seen. If there is more
* than one patched return address on our stack,
* complain loudly.
*/
WARN_ON(ftrace_graph_get_ret_stack(current, 1));
}
#endif
frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC);
if (!frame) {
printk(KERN_ERR "Unable to allocate a dwarf frame\n");
UNWINDER_BUG();
}
INIT_LIST_HEAD(&frame->reg_list);
frame->flags = 0;
frame->prev = prev;
frame->return_addr = 0;
fde = dwarf_lookup_fde(pc);
if (!fde) {
/*
* This is our normal exit path. There are two reasons
* why we might exit here,
*
* a) pc has no asscociated DWARF frame info and so
* we don't know how to unwind this frame. This is
* usually the case when we're trying to unwind a
* frame that was called from some assembly code
* that has no DWARF info, e.g. syscalls.
*
* b) the DEBUG info for pc is bogus. There's
* really no way to distinguish this case from the
* case above, which sucks because we could print a
* warning here.
*/
goto bail;
}
cie = dwarf_lookup_cie(fde->cie_pointer);
frame->pc = fde->initial_location;
/* CIE initial instructions */
dwarf_cfa_execute_insns(cie->initial_instructions,
cie->instructions_end, cie, fde,
frame, pc);
/* FDE instructions */
dwarf_cfa_execute_insns(fde->instructions, fde->end, cie,
fde, frame, pc);
/* Calculate the CFA */
switch (frame->flags) {
case DWARF_FRAME_CFA_REG_OFFSET:
if (prev) {
reg = dwarf_frame_reg(prev, frame->cfa_register);
UNWINDER_BUG_ON(!reg);
UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
addr = prev->cfa + reg->addr;
frame->cfa = __raw_readl(addr);
} else {
/*
* Again, we're starting from the top of the
* stack. We need to physically read
* the contents of a register in order to get
* the Canonical Frame Address for this
* function.
*/
frame->cfa = dwarf_read_arch_reg(frame->cfa_register);
}
frame->cfa += frame->cfa_offset;
break;
default:
UNWINDER_BUG();
}
reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG);
/*
* If we haven't seen the return address register or the return
* address column is undefined then we must assume that this is
* the end of the callstack.
*/
if (!reg || reg->flags == DWARF_UNDEFINED)
goto bail;
UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET);
addr = frame->cfa + reg->addr;
frame->return_addr = __raw_readl(addr);
/*
* Ah, the joys of unwinding through interrupts.
*
* Interrupts are tricky - the DWARF info needs to be _really_
* accurate and unfortunately I'm seeing a lot of bogus DWARF
* info. For example, I've seen interrupts occur in epilogues
* just after the frame pointer (r14) had been restored. The
* problem was that the DWARF info claimed that the CFA could be
* reached by using the value of the frame pointer before it was
* restored.
*
* So until the compiler can be trusted to produce reliable
* DWARF info when it really matters, let's stop unwinding once
* we've calculated the function that was interrupted.
*/
if (prev && prev->pc == (unsigned long)ret_from_irq)
frame->return_addr = 0;
return frame;
bail:
dwarf_free_frame(frame);
return NULL;
}
static int dwarf_parse_cie(void *entry, void *p, unsigned long len,
unsigned char *end, struct module *mod)
{
struct rb_node **rb_node = &cie_root.rb_node;
struct rb_node *parent = *rb_node;
struct dwarf_cie *cie;
unsigned long flags;
int count;
cie = kzalloc(sizeof(*cie), GFP_KERNEL);
if (!cie)
return -ENOMEM;
cie->length = len;
/*
* Record the offset into the .eh_frame section
* for this CIE. It allows this CIE to be
* quickly and easily looked up from the
* corresponding FDE.
*/
cie->cie_pointer = (unsigned long)entry;
cie->version = *(char *)p++;
UNWINDER_BUG_ON(cie->version != 1);
cie->augmentation = p;
p += strlen(cie->augmentation) + 1;
count = dwarf_read_uleb128(p, &cie->code_alignment_factor);
p += count;
count = dwarf_read_leb128(p, &cie->data_alignment_factor);
p += count;
/*
* Which column in the rule table contains the
* return address?
*/
if (cie->version == 1) {
cie->return_address_reg = __raw_readb(p);
p++;
} else {
count = dwarf_read_uleb128(p, &cie->return_address_reg);
p += count;
}
if (cie->augmentation[0] == 'z') {
unsigned int length, count;
cie->flags |= DWARF_CIE_Z_AUGMENTATION;
count = dwarf_read_uleb128(p, &length);
p += count;
UNWINDER_BUG_ON((unsigned char *)p > end);
cie->initial_instructions = p + length;
cie->augmentation++;
}
while (*cie->augmentation) {
/*
* "L" indicates a byte showing how the
* LSDA pointer is encoded. Skip it.
*/
if (*cie->augmentation == 'L') {
p++;
cie->augmentation++;
} else if (*cie->augmentation == 'R') {
/*
* "R" indicates a byte showing
* how FDE addresses are
* encoded.
*/
cie->encoding = *(char *)p++;
cie->augmentation++;
} else if (*cie->augmentation == 'P') {
/*
* "R" indicates a personality
* routine in the CIE
* augmentation.
*/
UNWINDER_BUG();
} else if (*cie->augmentation == 'S') {
UNWINDER_BUG();
} else {
/*
* Unknown augmentation. Assume
* 'z' augmentation.
*/
p = cie->initial_instructions;
UNWINDER_BUG_ON(!p);
break;
}
}
cie->initial_instructions = p;
cie->instructions_end = end;
/* Add to list */
spin_lock_irqsave(&dwarf_cie_lock, flags);
while (*rb_node) {
struct dwarf_cie *cie_tmp;
cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node);
parent = *rb_node;
if (cie->cie_pointer < cie_tmp->cie_pointer)
rb_node = &parent->rb_left;
else if (cie->cie_pointer >= cie_tmp->cie_pointer)
rb_node = &parent->rb_right;
else
WARN_ON(1);
}
rb_link_node(&cie->node, parent, rb_node);
rb_insert_color(&cie->node, &cie_root);
#ifdef CONFIG_MODULES
if (mod != NULL)
list_add_tail(&cie->link, &mod->arch.cie_list);
#endif
spin_unlock_irqrestore(&dwarf_cie_lock, flags);
return 0;
}
static int dwarf_parse_fde(void *entry, u32 entry_type,
void *start, unsigned long len,
unsigned char *end, struct module *mod)
{
struct rb_node **rb_node = &fde_root.rb_node;
struct rb_node *parent = *rb_node;
struct dwarf_fde *fde;
struct dwarf_cie *cie;
unsigned long flags;
int count;
void *p = start;
fde = kzalloc(sizeof(*fde), GFP_KERNEL);
if (!fde)
return -ENOMEM;
fde->length = len;
/*
* In a .eh_frame section the CIE pointer is the
* delta between the address within the FDE
*/
fde->cie_pointer = (unsigned long)(p - entry_type - 4);
cie = dwarf_lookup_cie(fde->cie_pointer);
fde->cie = cie;
if (cie->encoding)
count = dwarf_read_encoded_value(p, &fde->initial_location,
cie->encoding);
else
count = dwarf_read_addr(p, &fde->initial_location);
p += count;
if (cie->encoding)
count = dwarf_read_encoded_value(p, &fde->address_range,
cie->encoding & 0x0f);
else
count = dwarf_read_addr(p, &fde->address_range);
p += count;
if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) {
unsigned int length;
count = dwarf_read_uleb128(p, &length);
p += count + length;
}
/* Call frame instructions. */
fde->instructions = p;
fde->end = end;
/* Add to list. */
spin_lock_irqsave(&dwarf_fde_lock, flags);
while (*rb_node) {
struct dwarf_fde *fde_tmp;
unsigned long tmp_start, tmp_end;
unsigned long start, end;
fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node);
start = fde->initial_location;
end = fde->initial_location + fde->address_range;
tmp_start = fde_tmp->initial_location;
tmp_end = fde_tmp->initial_location + fde_tmp->address_range;
parent = *rb_node;
if (start < tmp_start)
rb_node = &parent->rb_left;
else if (start >= tmp_end)
rb_node = &parent->rb_right;
else
WARN_ON(1);
}
rb_link_node(&fde->node, parent, rb_node);
rb_insert_color(&fde->node, &fde_root);
#ifdef CONFIG_MODULES
if (mod != NULL)
list_add_tail(&fde->link, &mod->arch.fde_list);
#endif
spin_unlock_irqrestore(&dwarf_fde_lock, flags);
return 0;
}
static void dwarf_unwinder_dump(struct task_struct *task,
struct pt_regs *regs,
unsigned long *sp,
const struct stacktrace_ops *ops,
void *data)
{
struct dwarf_frame *frame, *_frame;
unsigned long return_addr;
_frame = NULL;
return_addr = 0;
while (1) {
frame = dwarf_unwind_stack(return_addr, _frame);
if (_frame)
dwarf_free_frame(_frame);
_frame = frame;
if (!frame || !frame->return_addr)
break;
return_addr = frame->return_addr;
ops->address(data, return_addr, 1);
}
if (frame)
dwarf_free_frame(frame);
}
static struct unwinder dwarf_unwinder = {
.name = "dwarf-unwinder",
.dump = dwarf_unwinder_dump,
.rating = 150,
};
static void __init dwarf_unwinder_cleanup(void)
{
struct dwarf_fde *fde, *next_fde;
struct dwarf_cie *cie, *next_cie;
/*
* Deallocate all the memory allocated for the DWARF unwinder.
* Traverse all the FDE/CIE lists and remove and free all the
* memory associated with those data structures.
*/
rbtree_postorder_for_each_entry_safe(fde, next_fde, &fde_root, node)
kfree(fde);
rbtree_postorder_for_each_entry_safe(cie, next_cie, &cie_root, node)
kfree(cie);
mempool_destroy(dwarf_reg_pool);
mempool_destroy(dwarf_frame_pool);
kmem_cache_destroy(dwarf_reg_cachep);
kmem_cache_destroy(dwarf_frame_cachep);
}
/**
* dwarf_parse_section - parse DWARF section
* @eh_frame_start: start address of the .eh_frame section
* @eh_frame_end: end address of the .eh_frame section
* @mod: the kernel module containing the .eh_frame section
*
* Parse the information in a .eh_frame section.
*/
static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end,
struct module *mod)
{
u32 entry_type;
void *p, *entry;
int count, err = 0;
unsigned long len = 0;
unsigned int c_entries, f_entries;
unsigned char *end;
c_entries = 0;
f_entries = 0;
entry = eh_frame_start;
while ((char *)entry < eh_frame_end) {
p = entry;
count = dwarf_entry_len(p, &len);
if (count == 0) {
/*
* We read a bogus length field value. There is
* nothing we can do here apart from disabling
* the DWARF unwinder. We can't even skip this
* entry and move to the next one because 'len'
* tells us where our next entry is.
*/
err = -EINVAL;
goto out;
} else
p += count;
/* initial length does not include itself */
end = p + len;
entry_type = get_unaligned((u32 *)p);
p += 4;
if (entry_type == DW_EH_FRAME_CIE) {
err = dwarf_parse_cie(entry, p, len, end, mod);
if (err < 0)
goto out;
else
c_entries++;
} else {
err = dwarf_parse_fde(entry, entry_type, p, len,
end, mod);
if (err < 0)
goto out;
else
f_entries++;
}
entry = (char *)entry + len + 4;
}
printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n",
c_entries, f_entries);
return 0;
out:
return err;
}
#ifdef CONFIG_MODULES
int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
struct module *me)
{
unsigned int i, err;
unsigned long start, end;
char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
start = end = 0;
for (i = 1; i < hdr->e_shnum; i++) {
/* Alloc bit cleared means "ignore it." */
if ((sechdrs[i].sh_flags & SHF_ALLOC)
&& !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) {
start = sechdrs[i].sh_addr;
end = start + sechdrs[i].sh_size;
break;
}
}
/* Did we find the .eh_frame section? */
if (i != hdr->e_shnum) {
INIT_LIST_HEAD(&me->arch.cie_list);
INIT_LIST_HEAD(&me->arch.fde_list);
err = dwarf_parse_section((char *)start, (char *)end, me);
if (err) {
printk(KERN_WARNING "%s: failed to parse DWARF info\n",
me->name);
return err;
}
}
return 0;
}
/**
* module_dwarf_cleanup - remove FDE/CIEs associated with @mod
* @mod: the module that is being unloaded
*
* Remove any FDEs and CIEs from the global lists that came from
* @mod's .eh_frame section because @mod is being unloaded.
*/
void module_dwarf_cleanup(struct module *mod)
{
struct dwarf_fde *fde, *ftmp;
struct dwarf_cie *cie, *ctmp;
unsigned long flags;
spin_lock_irqsave(&dwarf_cie_lock, flags);
list_for_each_entry_safe(cie, ctmp, &mod->arch.cie_list, link) {
list_del(&cie->link);
rb_erase(&cie->node, &cie_root);
kfree(cie);
}
spin_unlock_irqrestore(&dwarf_cie_lock, flags);
spin_lock_irqsave(&dwarf_fde_lock, flags);
list_for_each_entry_safe(fde, ftmp, &mod->arch.fde_list, link) {
list_del(&fde->link);
rb_erase(&fde->node, &fde_root);
kfree(fde);
}
spin_unlock_irqrestore(&dwarf_fde_lock, flags);
}
#endif /* CONFIG_MODULES */
/**
* dwarf_unwinder_init - initialise the dwarf unwinder
*
* Build the data structures describing the .dwarf_frame section to
* make it easier to lookup CIE and FDE entries. Because the
* .eh_frame section is packed as tightly as possible it is not
* easy to lookup the FDE for a given PC, so we build a list of FDE
* and CIE entries that make it easier.
*/
static int __init dwarf_unwinder_init(void)
{
int err = -ENOMEM;
dwarf_frame_cachep = kmem_cache_create("dwarf_frames",
sizeof(struct dwarf_frame), 0,
SLAB_PANIC | SLAB_HWCACHE_ALIGN, NULL);
dwarf_reg_cachep = kmem_cache_create("dwarf_regs",
sizeof(struct dwarf_reg), 0,
SLAB_PANIC | SLAB_HWCACHE_ALIGN, NULL);
dwarf_frame_pool = mempool_create_slab_pool(DWARF_FRAME_MIN_REQ,
dwarf_frame_cachep);
if (!dwarf_frame_pool)
goto out;
dwarf_reg_pool = mempool_create_slab_pool(DWARF_REG_MIN_REQ,
dwarf_reg_cachep);
if (!dwarf_reg_pool)
goto out;
err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL);
if (err)
goto out;
err = unwinder_register(&dwarf_unwinder);
if (err)
goto out;
dwarf_unwinder_ready = 1;
return 0;
out:
printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err);
dwarf_unwinder_cleanup();
return err;
}
early_initcall(dwarf_unwinder_init);