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[PATCH] unwinder: Add debugging output to the Dwarf2 unwinder
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Add debugging printks to the unwinder to allow easier debugging
when something goes wrong with it.

This can be controlled with the new unwinder_debug=N option
Most output is given by N=1

AK: Added documentation of unwinder_debug=

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
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Jan Beulich authored and Andi Kleen committed Dec 7, 2006
1 parent 3807fd4 commit 6d0185e
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Showing 2 changed files with 99 additions and 17 deletions.
3 changes: 3 additions & 0 deletions Documentation/kernel-parameters.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1735,6 +1735,9 @@ and is between 256 and 4096 characters. It is defined in the file
norandmaps Don't use address space randomization
Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space

unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
This is useful to get more information why
you got a "dwarf2 unwinder stuck"

______________________________________________________________________

Expand Down
113 changes: 96 additions & 17 deletions kernel/unwind.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -137,6 +137,17 @@ struct unwind_state {

static const struct cfa badCFA = { ARRAY_SIZE(reg_info), 1 };

static unsigned unwind_debug;
static int __init unwind_debug_setup(char *s)
{
unwind_debug = simple_strtoul(s, NULL, 0);
return 1;
}
__setup("unwind_debug=", unwind_debug_setup);
#define dprintk(lvl, fmt, args...) \
((void)(lvl > unwind_debug \
|| printk(KERN_DEBUG "unwind: " fmt "\n", ##args)))

static struct unwind_table *find_table(unsigned long pc)
{
struct unwind_table *table;
Expand Down Expand Up @@ -281,6 +292,7 @@ static void __init setup_unwind_table(struct unwind_table *table,

hdrSize = 4 + sizeof(unsigned long) + sizeof(unsigned int)
+ 2 * n * sizeof(unsigned long);
dprintk(2, "Binary lookup table size for %s: %lu bytes", table->name, hdrSize);
header = alloc(hdrSize);
if (!header)
return;
Expand Down Expand Up @@ -500,22 +512,28 @@ static unsigned long read_pointer(const u8 **pLoc,
const unsigned long *pul;
} ptr;

if (ptrType < 0 || ptrType == DW_EH_PE_omit)
if (ptrType < 0 || ptrType == DW_EH_PE_omit) {
dprintk(1, "Invalid pointer encoding %02X (%p,%p).", ptrType, *pLoc, end);
return 0;
}
ptr.p8 = *pLoc;
switch(ptrType & DW_EH_PE_FORM) {
case DW_EH_PE_data2:
if (end < (const void *)(ptr.p16u + 1))
if (end < (const void *)(ptr.p16u + 1)) {
dprintk(1, "Data16 overrun (%p,%p).", ptr.p8, end);
return 0;
}
if(ptrType & DW_EH_PE_signed)
value = get_unaligned(ptr.p16s++);
else
value = get_unaligned(ptr.p16u++);
break;
case DW_EH_PE_data4:
#ifdef CONFIG_64BIT
if (end < (const void *)(ptr.p32u + 1))
if (end < (const void *)(ptr.p32u + 1)) {
dprintk(1, "Data32 overrun (%p,%p).", ptr.p8, end);
return 0;
}
if(ptrType & DW_EH_PE_signed)
value = get_unaligned(ptr.p32s++);
else
Expand All @@ -527,19 +545,25 @@ static unsigned long read_pointer(const u8 **pLoc,
BUILD_BUG_ON(sizeof(u32) != sizeof(value));
#endif
case DW_EH_PE_native:
if (end < (const void *)(ptr.pul + 1))
if (end < (const void *)(ptr.pul + 1)) {
dprintk(1, "DataUL overrun (%p,%p).", ptr.p8, end);
return 0;
}
value = get_unaligned(ptr.pul++);
break;
case DW_EH_PE_leb128:
BUILD_BUG_ON(sizeof(uleb128_t) > sizeof(value));
value = ptrType & DW_EH_PE_signed
? get_sleb128(&ptr.p8, end)
: get_uleb128(&ptr.p8, end);
if ((const void *)ptr.p8 > end)
if ((const void *)ptr.p8 > end) {
dprintk(1, "DataLEB overrun (%p,%p).", ptr.p8, end);
return 0;
}
break;
default:
dprintk(2, "Cannot decode pointer type %02X (%p,%p).",
ptrType, ptr.p8, end);
return 0;
}
switch(ptrType & DW_EH_PE_ADJUST) {
Expand All @@ -549,11 +573,16 @@ static unsigned long read_pointer(const u8 **pLoc,
value += (unsigned long)*pLoc;
break;
default:
dprintk(2, "Cannot adjust pointer type %02X (%p,%p).",
ptrType, *pLoc, end);
return 0;
}
if ((ptrType & DW_EH_PE_indirect)
&& probe_kernel_address((unsigned long *)value, value))
&& probe_kernel_address((unsigned long *)value, value)) {
dprintk(1, "Cannot read indirect value %lx (%p,%p).",
value, *pLoc, end);
return 0;
}
*pLoc = ptr.p8;

return value;
Expand Down Expand Up @@ -702,8 +731,10 @@ static int processCFI(const u8 *start,
state->label = NULL;
return 1;
}
if (state->stackDepth >= MAX_STACK_DEPTH)
if (state->stackDepth >= MAX_STACK_DEPTH) {
dprintk(1, "State stack overflow (%p,%p).", ptr.p8, end);
return 0;
}
state->stack[state->stackDepth++] = ptr.p8;
break;
case DW_CFA_restore_state:
Expand All @@ -718,8 +749,10 @@ static int processCFI(const u8 *start,
result = processCFI(start, end, 0, ptrType, state);
state->loc = loc;
state->label = label;
} else
} else {
dprintk(1, "State stack underflow (%p,%p).", ptr.p8, end);
return 0;
}
break;
case DW_CFA_def_cfa:
state->cfa.reg = get_uleb128(&ptr.p8, end);
Expand Down Expand Up @@ -751,6 +784,7 @@ static int processCFI(const u8 *start,
break;
case DW_CFA_GNU_window_save:
default:
dprintk(1, "Unrecognized CFI op %02X (%p,%p).", ptr.p8[-1], ptr.p8 - 1, end);
result = 0;
break;
}
Expand All @@ -766,12 +800,17 @@ static int processCFI(const u8 *start,
set_rule(*ptr.p8++ & 0x3f, Nowhere, 0, state);
break;
}
if (ptr.p8 > end)
if (ptr.p8 > end) {
dprintk(1, "Data overrun (%p,%p).", ptr.p8, end);
result = 0;
}
if (result && targetLoc != 0 && targetLoc < state->loc)
return 1;
}

if (result && ptr.p8 < end)
dprintk(1, "Data underrun (%p,%p).", ptr.p8, end);

return result
&& ptr.p8 == end
&& (targetLoc == 0
Expand Down Expand Up @@ -843,6 +882,8 @@ int unwind(struct unwind_frame_info *frame)
hdr[3]);
}
}
if(hdr && !fde)
dprintk(3, "Binary lookup for %lx failed.", pc);

if (fde != NULL) {
cie = cie_for_fde(fde, table);
Expand All @@ -864,6 +905,8 @@ int unwind(struct unwind_frame_info *frame)
fde = NULL;
} else
fde = NULL;
if(!fde)
dprintk(1, "Binary lookup result for %lx discarded.", pc);
}
if (fde == NULL) {
for (fde = table->address, tableSize = table->size;
Expand Down Expand Up @@ -895,6 +938,8 @@ int unwind(struct unwind_frame_info *frame)
if (pc >= startLoc && pc < endLoc)
break;
}
if(!fde)
dprintk(3, "Linear lookup for %lx failed.", pc);
}
}
if (cie != NULL) {
Expand Down Expand Up @@ -928,6 +973,8 @@ int unwind(struct unwind_frame_info *frame)
if (ptr >= end || *ptr)
cie = NULL;
}
if(!cie)
dprintk(1, "CIE unusable (%p,%p).", ptr, end);
++ptr;
}
if (cie != NULL) {
Expand All @@ -938,9 +985,11 @@ int unwind(struct unwind_frame_info *frame)
if (state.codeAlign == 0 || state.dataAlign == 0 || ptr >= end)
cie = NULL;
else if (UNW_PC(frame) % state.codeAlign
|| UNW_SP(frame) % sleb128abs(state.dataAlign))
|| UNW_SP(frame) % sleb128abs(state.dataAlign)) {
dprintk(1, "Input pointer(s) misaligned (%lx,%lx).",
UNW_PC(frame), UNW_SP(frame));
return -EPERM;
else {
} else {
retAddrReg = state.version <= 1 ? *ptr++ : get_uleb128(&ptr, end);
/* skip augmentation */
if (((const char *)(cie + 2))[1] == 'z') {
Expand All @@ -954,6 +1003,8 @@ int unwind(struct unwind_frame_info *frame)
|| reg_info[retAddrReg].width != sizeof(unsigned long))
cie = NULL;
}
if(!cie)
dprintk(1, "CIE validation failed (%p,%p).", ptr, end);
}
if (cie != NULL) {
state.cieStart = ptr;
Expand All @@ -967,6 +1018,8 @@ int unwind(struct unwind_frame_info *frame)
if ((ptr += augSize) > end)
fde = NULL;
}
if(!fde)
dprintk(1, "FDE validation failed (%p,%p).", ptr, end);
}
if (cie == NULL || fde == NULL) {
#ifdef CONFIG_FRAME_POINTER
Expand Down Expand Up @@ -1025,8 +1078,10 @@ int unwind(struct unwind_frame_info *frame)
|| state.cfa.reg >= ARRAY_SIZE(reg_info)
|| reg_info[state.cfa.reg].width != sizeof(unsigned long)
|| FRAME_REG(state.cfa.reg, unsigned long) % sizeof(unsigned long)
|| state.cfa.offs % sizeof(unsigned long))
|| state.cfa.offs % sizeof(unsigned long)) {
dprintk(1, "Unusable unwind info (%p,%p).", ptr, end);
return -EIO;
}
/* update frame */
#ifndef CONFIG_AS_CFI_SIGNAL_FRAME
if(frame->call_frame
Expand All @@ -1051,6 +1106,8 @@ int unwind(struct unwind_frame_info *frame)
if (REG_INVALID(i)) {
if (state.regs[i].where == Nowhere)
continue;
dprintk(1, "Cannot restore register %u (%d).",
i, state.regs[i].where);
return -EIO;
}
switch(state.regs[i].where) {
Expand All @@ -1059,8 +1116,11 @@ int unwind(struct unwind_frame_info *frame)
case Register:
if (state.regs[i].value >= ARRAY_SIZE(reg_info)
|| REG_INVALID(state.regs[i].value)
|| reg_info[i].width > reg_info[state.regs[i].value].width)
|| reg_info[i].width > reg_info[state.regs[i].value].width) {
dprintk(1, "Cannot restore register %u from register %lu.",
i, state.regs[i].value);
return -EIO;
}
switch(reg_info[state.regs[i].value].width) {
#define CASE(n) \
case sizeof(u##n): \
Expand All @@ -1070,6 +1130,9 @@ int unwind(struct unwind_frame_info *frame)
CASES;
#undef CASE
default:
dprintk(1, "Unsupported register size %u (%lu).",
reg_info[state.regs[i].value].width,
state.regs[i].value);
return -EIO;
}
break;
Expand All @@ -1094,12 +1157,17 @@ int unwind(struct unwind_frame_info *frame)
CASES;
#undef CASE
default:
dprintk(1, "Unsupported register size %u (%u).",
reg_info[i].width, i);
return -EIO;
}
break;
case Value:
if (reg_info[i].width != sizeof(unsigned long))
if (reg_info[i].width != sizeof(unsigned long)) {
dprintk(1, "Unsupported value size %u (%u).",
reg_info[i].width, i);
return -EIO;
}
FRAME_REG(i, unsigned long) = cfa + state.regs[i].value
* state.dataAlign;
break;
Expand All @@ -1111,15 +1179,20 @@ int unwind(struct unwind_frame_info *frame)
% sizeof(unsigned long)
|| addr < startLoc
|| addr + sizeof(unsigned long) < addr
|| addr + sizeof(unsigned long) > endLoc)
|| addr + sizeof(unsigned long) > endLoc) {
dprintk(1, "Bad memory location %lx (%lx).",
addr, state.regs[i].value);
return -EIO;
}
switch(reg_info[i].width) {
#define CASE(n) case sizeof(u##n): \
probe_kernel_address((u##n *)addr, FRAME_REG(i, u##n)); \
break
CASES;
#undef CASE
default:
dprintk(1, "Unsupported memory size %u (%u).",
reg_info[i].width, i);
return -EIO;
}
}
Expand All @@ -1128,9 +1201,15 @@ int unwind(struct unwind_frame_info *frame)
}

if (UNW_PC(frame) % state.codeAlign
|| UNW_SP(frame) % sleb128abs(state.dataAlign)
|| (pc == UNW_PC(frame) && sp == UNW_SP(frame)))
|| UNW_SP(frame) % sleb128abs(state.dataAlign)) {
dprintk(1, "Output pointer(s) misaligned (%lx,%lx).",
UNW_PC(frame), UNW_SP(frame));
return -EIO;
}
if (pc == UNW_PC(frame) && sp == UNW_SP(frame)) {
dprintk(1, "No progress (%lx,%lx).", pc, sp);
return -EIO;
}

return 0;
#undef CASES
Expand Down

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