linux/arch/sh/kernel/dwarf.c

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// 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 cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 08:04:11 +00:00
#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(&reg->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(&reg->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
*/
static 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, &reg);
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, &reg);
current_insn += count;
break;
case DW_CFA_undefined:
count = dwarf_read_uleb128(current_insn, &reg);
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, &reg);
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, &reg);
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, &reg);
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);