[PATCH] unwinder: Add debugging output to the Dwarf2 unwinder
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>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4e90aa4..d34fd6a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1735,6 +1735,9 @@
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"
______________________________________________________________________
diff --git a/kernel/unwind.c b/kernel/unwind.c
index 7e721f1..209e248 100644
--- a/kernel/unwind.c
+++ b/kernel/unwind.c
@@ -137,6 +137,17 @@
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;
@@ -281,6 +292,7 @@
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;
@@ -500,13 +512,17 @@
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
@@ -514,8 +530,10 @@
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
@@ -527,8 +545,10 @@
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:
@@ -536,10 +556,14 @@
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) {
@@ -549,11 +573,16 @@
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;
@@ -702,8 +731,10 @@
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:
@@ -718,8 +749,10 @@
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);
@@ -751,6 +784,7 @@
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;
}
@@ -766,12 +800,17 @@
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
@@ -843,6 +882,8 @@
hdr[3]);
}
}
+ if(hdr && !fde)
+ dprintk(3, "Binary lookup for %lx failed.", pc);
if (fde != NULL) {
cie = cie_for_fde(fde, table);
@@ -864,6 +905,8 @@
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;
@@ -895,6 +938,8 @@
if (pc >= startLoc && pc < endLoc)
break;
}
+ if(!fde)
+ dprintk(3, "Linear lookup for %lx failed.", pc);
}
}
if (cie != NULL) {
@@ -928,6 +973,8 @@
if (ptr >= end || *ptr)
cie = NULL;
}
+ if(!cie)
+ dprintk(1, "CIE unusable (%p,%p).", ptr, end);
++ptr;
}
if (cie != NULL) {
@@ -938,9 +985,11 @@
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') {
@@ -954,6 +1003,8 @@
|| 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;
@@ -967,6 +1018,8 @@
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
@@ -1025,8 +1078,10 @@
|| 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
@@ -1051,6 +1106,8 @@
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) {
@@ -1059,8 +1116,11 @@
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): \
@@ -1070,6 +1130,9 @@
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;
@@ -1094,12 +1157,17 @@
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;
@@ -1111,8 +1179,11 @@
% 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)); \
@@ -1120,6 +1191,8 @@
CASES;
#undef CASE
default:
+ dprintk(1, "Unsupported memory size %u (%u).",
+ reg_info[i].width, i);
return -EIO;
}
}
@@ -1128,9 +1201,15 @@
}
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