[4.2.y-ckt stable] Patch "ARC: dw2 unwind: Reinstante unwinding out of modules" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ARC: dw2 unwind: Reinstante unwinding out of modules

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 6b18103533ae5b77da72712a72fd87d11aeecd1f Mon Sep 17 00:00:00 2001
From: Vineet Gupta <vgupta at synopsys.com>
Date: Fri, 11 Dec 2015 18:04:22 +0530
Subject: ARC: dw2 unwind: Reinstante unwinding out of modules

commit bc79c9a7216562a2035d2f64f73626613c1300d0 upstream.

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 <vgupta at synopsys.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 7ca628b..c11a25b 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 cabde9d..4940732 100644
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -432,7 +432,6 @@ 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 7352475..9f9ecc1 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