Wreckage of removal of slowpath linear search
Vineet Gupta (2):
ARC: dw2 unwind: Reinstante unwinding out of modules
ARC: dw2 unwind: Ignore CIE version !=1 gracefully instead of bailing
arch/arc/include/asm/unwind.h | 4 ----
arch/arc/kernel/setup.c | 1 -
arch/arc/kernel/unwind.c | 53 ++++++++++++++++++++++++++++---------------
3 files changed, 35 insertions(+), 23 deletions(-)
--
1.9.1
The fix which removed linear searching of dwarf (because binary lookup
data always exists) missed out on the fact that modules don't get the
binary lookup tables info. This caused unwinding out of modules to stop
working.
So add binary lookup header setup (equivalent of eh_frame_hdr setup) to
modules as well.
While at it, confine the header setup to within unwinder code,
reducing one API exposed out of unwinder code.
Fixes: 2e22502c080f ARC: dw2 unwind: Remove falllback linear search thru FDE entries
Signed-off-by: Vineet Gupta <[email protected]>
---
arch/arc/include/asm/unwind.h | 4 ----
arch/arc/kernel/setup.c | 1 -
arch/arc/kernel/unwind.c | 40 ++++++++++++++++++++++++++--------------
3 files changed, 26 insertions(+), 19 deletions(-)
diff --git a/arch/arc/include/asm/unwind.h b/arch/arc/include/asm/unwind.h
index 7ca628b6ee2a..c11a25bb8158 100644
--- a/arch/arc/include/asm/unwind.h
+++ b/arch/arc/include/asm/unwind.h
@@ -112,7 +112,6 @@ struct unwind_frame_info {
extern int arc_unwind(struct unwind_frame_info *frame);
extern void arc_unwind_init(void);
-extern void arc_unwind_setup(void);
extern void *unwind_add_table(struct module *module, const void *table_start,
unsigned long table_size);
extern void unwind_remove_table(void *handle, int init_only);
@@ -152,9 +151,6 @@ static inline void arc_unwind_init(void)
{
}
-static inline void arc_unwind_setup(void)
-{
-}
#define unwind_add_table(a, b, c)
#define unwind_remove_table(a, b)
diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
index c33e77c0ad3e..e1b87444ea9a 100644
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -429,7 +429,6 @@ void __init setup_arch(char **cmdline_p)
#endif
arc_unwind_init();
- arc_unwind_setup();
}
static int __init customize_machine(void)
diff --git a/arch/arc/kernel/unwind.c b/arch/arc/kernel/unwind.c
index 7352475451f6..9f9ecc15556e 100644
--- a/arch/arc/kernel/unwind.c
+++ b/arch/arc/kernel/unwind.c
@@ -170,6 +170,23 @@ static struct unwind_table *find_table(unsigned long pc)
static unsigned long read_pointer(const u8 **pLoc,
const void *end, signed ptrType);
+static void init_unwind_hdr(struct unwind_table *table,
+ void *(*alloc) (unsigned long));
+
+/*
+ * wrappers for header alloc (vs. calling one vs. other at call site)
+ * to elide section mismatches warnings
+ */
+static void *__init unw_hdr_alloc_early(unsigned long sz)
+{
+ return __alloc_bootmem_nopanic(sz, sizeof(unsigned int),
+ MAX_DMA_ADDRESS);
+}
+
+static void *unw_hdr_alloc(unsigned long sz)
+{
+ return kmalloc(sz, GFP_KERNEL);
+}
static void init_unwind_table(struct unwind_table *table, const char *name,
const void *core_start, unsigned long core_size,
@@ -209,6 +226,8 @@ void __init arc_unwind_init(void)
__start_unwind, __end_unwind - __start_unwind,
NULL, 0);
/*__start_unwind_hdr, __end_unwind_hdr - __start_unwind_hdr);*/
+
+ init_unwind_hdr(&root_table, unw_hdr_alloc_early);
}
static const u32 bad_cie, not_fde;
@@ -241,8 +260,8 @@ static void swap_eh_frame_hdr_table_entries(void *p1, void *p2, int size)
e2->fde = v;
}
-static void __init setup_unwind_table(struct unwind_table *table,
- void *(*alloc) (unsigned long))
+static void init_unwind_hdr(struct unwind_table *table,
+ void *(*alloc) (unsigned long))
{
const u8 *ptr;
unsigned long tableSize = table->size, hdrSize;
@@ -300,9 +319,11 @@ static void __init setup_unwind_table(struct unwind_table *table,
hdrSize = 4 + sizeof(unsigned long) + sizeof(unsigned int)
+ 2 * n * sizeof(unsigned long);
+
header = alloc(hdrSize);
if (!header)
return;
+
header->version = 1;
header->eh_frame_ptr_enc = DW_EH_PE_abs | DW_EH_PE_native;
header->fde_count_enc = DW_EH_PE_abs | DW_EH_PE_data4;
@@ -342,18 +363,6 @@ static void __init setup_unwind_table(struct unwind_table *table,
table->header = (const void *)header;
}
-static void *__init balloc(unsigned long sz)
-{
- return __alloc_bootmem_nopanic(sz,
- sizeof(unsigned int),
- __pa(MAX_DMA_ADDRESS));
-}
-
-void __init arc_unwind_setup(void)
-{
- setup_unwind_table(&root_table, balloc);
-}
-
#ifdef CONFIG_MODULES
static struct unwind_table *last_table;
@@ -377,6 +386,8 @@ void *unwind_add_table(struct module *module, const void *table_start,
table_start, table_size,
NULL, 0);
+ init_unwind_hdr(table, unw_hdr_alloc);
+
#ifdef UNWIND_DEBUG
unw_debug("Table added for [%s] %lx %lx\n",
module->name, table->core.pc, table->core.range);
@@ -439,6 +450,7 @@ void unwind_remove_table(void *handle, int init_only)
info.init_only = init_only;
unlink_table(&info); /* XXX: SMP */
+ kfree(table->header);
kfree(table);
}
--
1.9.1
ARC dwarf unwinder only supports CIE version == 1
The boot time dwarf sanitizer (part of binary lookup table constructor)
would simply bail if it saw CIE version == 3, rendering unwinder with a
NULL lookup table.
It seems libgcc linked with kernel does have such entries.
With fallback linear search removed, and a NULL binary lookup table,
unwinder fails to generate any stack trace.
So allow graceful ignoring of unsupported CIE entries.
This problem was initially seen in Alexey's setup (and not mine) as he
was using buildroot built toolchain (libgcc) which doesn't get built with
CFLAGS_FOR_TARGET="-gdwarf-2 which is my default
Fixes STAR 9000985048: "kernel unwinder broken with stock tools"
Fixes: 2e22502c080f ARC: dw2 unwind: Remove falllback linear search thru FDE entries
Reported-by Alexey Brodkin <[email protected]>
Signed-off-by: Vineet Gupta <[email protected]>
Signed-off-by: Vineet Gupta <[email protected]>
---
arch/arc/kernel/unwind.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/arc/kernel/unwind.c b/arch/arc/kernel/unwind.c
index 9f9ecc15556e..cf2828ab0905 100644
--- a/arch/arc/kernel/unwind.c
+++ b/arch/arc/kernel/unwind.c
@@ -293,13 +293,13 @@ static void init_unwind_hdr(struct unwind_table *table,
const u32 *cie = cie_for_fde(fde, table);
signed ptrType;
- if (cie == ¬_fde)
+ if (cie == ¬_fde) /* only process FDE here */
continue;
if (cie == NULL || cie == &bad_cie)
- return;
+ continue; /* say FDE->CIE.version != 1 */
ptrType = fde_pointer_type(cie);
if (ptrType < 0)
- return;
+ continue;
ptr = (const u8 *)(fde + 2);
if (!read_pointer(&ptr, (const u8 *)(fde + 1) + *fde,
@@ -343,6 +343,10 @@ static void init_unwind_hdr(struct unwind_table *table,
if (fde[1] == 0xffffffff)
continue; /* this is a CIE */
+
+ if (*(u8 *)(cie + 2) != 1)
+ continue; /* FDE->CIE.version not supported */
+
ptr = (const u8 *)(fde + 2);
header->table[n].start = read_pointer(&ptr,
(const u8 *)(fde + 1) +
@@ -519,7 +523,8 @@ static const u32 *cie_for_fde(const u32 *fde, const struct unwind_table *table)
if (*cie <= sizeof(*cie) + 4 || *cie >= fde[1] - sizeof(*fde)
|| (*cie & (sizeof(*cie) - 1))
- || (cie[1] != 0xffffffff))
+ || (cie[1] != 0xffffffff)
+ || ( *(u8 *)(cie + 2) != 1)) /* version 1 supported */
return NULL; /* this is not a (valid) CIE */
return cie;
}
--
1.9.1