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[PATCH] unwinder: fully support linker generated .eh_frame_hdr section
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Now that binutils' ld is able to properly populate .eh_frame_hdr in the
Linux kernel case, here's a patch to add some functionality to the Dwarf2
unwinder to actually be able to make use of this (applies on firstfloor
tree with the previously sent patch to add debug output, but not on plain
2.6.19).

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 6bedb2c commit c65f38d
Showing 1 changed file with 47 additions and 19 deletions.
66 changes: 47 additions & 19 deletions kernel/unwind.c
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Original file line number Diff line number Diff line change
Expand Up @@ -164,7 +164,9 @@ static struct unwind_table *find_table(unsigned long pc)

static unsigned long read_pointer(const u8 **pLoc,
const void *end,
signed ptrType);
signed ptrType,
unsigned long text_base,
unsigned long data_base);

static void init_unwind_table(struct unwind_table *table,
const char *name,
Expand All @@ -189,10 +191,13 @@ static void init_unwind_table(struct unwind_table *table,
/* See if the linker provided table looks valid. */
if (header_size <= 4
|| header_start[0] != 1
|| (void *)read_pointer(&ptr, end, header_start[1]) != table_start
|| header_start[2] == DW_EH_PE_omit
|| read_pointer(&ptr, end, header_start[2]) <= 0
|| header_start[3] == DW_EH_PE_omit)
|| (void *)read_pointer(&ptr, end, header_start[1], 0, 0)
!= table_start
|| !read_pointer(&ptr, end, header_start[2], 0, 0)
|| !read_pointer(&ptr, end, header_start[3], 0,
(unsigned long)header_start)
|| !read_pointer(&ptr, end, header_start[3], 0,
(unsigned long)header_start))
header_start = NULL;
table->hdrsz = header_size;
smp_wmb();
Expand Down Expand Up @@ -282,7 +287,7 @@ static void __init setup_unwind_table(struct unwind_table *table,
ptr = (const u8 *)(fde + 2);
if (!read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType))
ptrType, 0, 0))
return;
++n;
}
Expand Down Expand Up @@ -317,7 +322,7 @@ static void __init setup_unwind_table(struct unwind_table *table,
ptr = (const u8 *)(fde + 2);
header->table[n].start = read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
fde_pointer_type(cie));
fde_pointer_type(cie), 0, 0);
header->table[n].fde = (unsigned long)fde;
++n;
}
Expand Down Expand Up @@ -500,7 +505,9 @@ static const u32 *cie_for_fde(const u32 *fde, const struct unwind_table *table)

static unsigned long read_pointer(const u8 **pLoc,
const void *end,
signed ptrType)
signed ptrType,
unsigned long text_base,
unsigned long data_base)
{
unsigned long value = 0;
union {
Expand Down Expand Up @@ -572,6 +579,22 @@ static unsigned long read_pointer(const u8 **pLoc,
case DW_EH_PE_pcrel:
value += (unsigned long)*pLoc;
break;
case DW_EH_PE_textrel:
if (likely(text_base)) {
value += text_base;
break;
}
dprintk(2, "Text-relative encoding %02X (%p,%p), but zero text base.",
ptrType, *pLoc, end);
return 0;
case DW_EH_PE_datarel:
if (likely(data_base)) {
value += data_base;
break;
}
dprintk(2, "Data-relative encoding %02X (%p,%p), but zero data base.",
ptrType, *pLoc, end);
return 0;
default:
dprintk(2, "Cannot adjust pointer type %02X (%p,%p).",
ptrType, *pLoc, end);
Expand Down Expand Up @@ -625,7 +648,8 @@ static signed fde_pointer_type(const u32 *cie)
case 'P': {
signed ptrType = *ptr++;

if (!read_pointer(&ptr, end, ptrType) || ptr > end)
if (!read_pointer(&ptr, end, ptrType, 0, 0)
|| ptr > end)
return -1;
}
break;
Expand Down Expand Up @@ -685,7 +709,8 @@ static int processCFI(const u8 *start,
case DW_CFA_nop:
break;
case DW_CFA_set_loc:
if ((state->loc = read_pointer(&ptr.p8, end, ptrType)) == 0)
state->loc = read_pointer(&ptr.p8, end, ptrType, 0, 0);
if (state->loc == 0)
result = 0;
break;
case DW_CFA_advance_loc1:
Expand Down Expand Up @@ -854,17 +879,18 @@ int unwind(struct unwind_frame_info *frame)
ptr = hdr + 4;
end = hdr + table->hdrsz;
if (tableSize
&& read_pointer(&ptr, end, hdr[1])
&& read_pointer(&ptr, end, hdr[1], 0, 0)
== (unsigned long)table->address
&& (i = read_pointer(&ptr, end, hdr[2])) > 0
&& (i = read_pointer(&ptr, end, hdr[2], 0, 0)) > 0
&& i == (end - ptr) / (2 * tableSize)
&& !((end - ptr) % (2 * tableSize))) {
do {
const u8 *cur = ptr + (i / 2) * (2 * tableSize);

startLoc = read_pointer(&cur,
cur + tableSize,
hdr[3]);
hdr[3], 0,
(unsigned long)hdr);
if (pc < startLoc)
i /= 2;
else {
Expand All @@ -875,11 +901,13 @@ int unwind(struct unwind_frame_info *frame)
if (i == 1
&& (startLoc = read_pointer(&ptr,
ptr + tableSize,
hdr[3])) != 0
hdr[3], 0,
(unsigned long)hdr)) != 0
&& pc >= startLoc)
fde = (void *)read_pointer(&ptr,
ptr + tableSize,
hdr[3]);
hdr[3], 0,
(unsigned long)hdr);
}
}
if(hdr && !fde)
Expand All @@ -894,13 +922,13 @@ int unwind(struct unwind_frame_info *frame)
&& (ptrType = fde_pointer_type(cie)) >= 0
&& read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType) == startLoc) {
ptrType, 0, 0) == startLoc) {
if (!(ptrType & DW_EH_PE_indirect))
ptrType &= DW_EH_PE_FORM|DW_EH_PE_signed;
endLoc = startLoc
+ read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType);
ptrType, 0, 0);
if(pc >= endLoc)
fde = NULL;
} else
Expand All @@ -926,15 +954,15 @@ int unwind(struct unwind_frame_info *frame)
ptr = (const u8 *)(fde + 2);
startLoc = read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType);
ptrType, 0, 0);
if (!startLoc)
continue;
if (!(ptrType & DW_EH_PE_indirect))
ptrType &= DW_EH_PE_FORM|DW_EH_PE_signed;
endLoc = startLoc
+ read_pointer(&ptr,
(const u8 *)(fde + 1) + *fde,
ptrType);
ptrType, 0, 0);
if (pc >= startLoc && pc < endLoc)
break;
}
Expand Down

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