ARC: DWARF2 .debug_frame based stack unwinder

-Originally written by Rajeshwar Ranga
-Derived off of generic unwinder in 2.6.19 and adapted to ARC

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Rajeshwar Ranga <rajeshwar.ranga@gmail.com>

1 files changed, 58 insertions, 0 deletions

diff --git a/arch/arc/kernel/module.c b/arch/arc/kernel/module.c
index a1bb70d6e97d..cdd359352c0a 100644
--- a/arch/arc/kernel/module.c
+++ b/arch/arc/kernel/module.c
@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/fs.h>
 #include <linux/string.h>
+#include <asm/unwind.h>
 
 static inline void arc_write_me(unsigned short *addr, unsigned long value)
 {
@@ -21,6 +22,42 @@ static inline void arc_write_me(unsigned short *addr, unsigned long value)
         *(addr + 1) = (value & 0xffff);
 }
 
+/* ARC specific section quirks - before relocation loop in generic loader
+ *
+ * For dwarf unwinding out of modules, this needs to
+ * 1. Ensure the .debug_frame is allocatable (ARC Linker bug: despite
+ *    -fasynchronous-unwind-tables it doesn't).
+ * 2. Since we are iterating thru sec hdr tbl anyways, make a note of
+ *    the exact section index, for later use.
+ */
+int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
+                              char *secstr, struct module *mod)
+{
+#ifdef CONFIG_ARC_DW2_UNWIND
+        int i;
+
+        mod->arch.unw_sec_idx = 0;
+        mod->arch.unw_info = NULL;
+
+        for (i = 1; i < hdr->e_shnum; i++) {
+                if (strcmp(secstr+sechdrs[i].sh_name, ".debug_frame") == 0) {
+                        sechdrs[i].sh_flags |= SHF_ALLOC;
+                        mod->arch.unw_sec_idx = i;
+                        break;
+                }
+        }
+#endif
+    return 0;
+}
+
+void module_arch_cleanup(struct module *mod)
+{
+#ifdef CONFIG_ARC_DW2_UNWIND
+        if (mod->arch.unw_info)
+                unwind_remove_table(mod->arch.unw_info, 0);
+#endif
+}
+
 int apply_relocate_add(Elf32_Shdr *sechdrs,
                        const char *strtab,
                        unsigned int symindex,   /* sec index for sym tbl */
@@ -85,3 +122,24 @@ relo_err:
         return -ENOEXEC;
 
 }
+
+/* Just before lift off: After sections have been relocated, we add the
+ * dwarf section to unwinder table pool
+ * This couldn't be done in module_frob_arch_sections() because
+ * relocations had not been applied by then
+ */
+int module_finalize(const Elf32_Ehdr *hdr, const Elf_Shdr *sechdrs,
+                    struct module *mod)
+{
+#ifdef CONFIG_ARC_DW2_UNWIND
+        void *unw;
+        int unwsec = mod->arch.unw_sec_idx;
+
+        if (unwsec) {
+                unw = unwind_add_table(mod, (void *)sechdrs[unwsec].sh_addr,
+                                       sechdrs[unwsec].sh_size);
+                mod->arch.unw_info = unw;
+        }
+#endif
+    return 0;
+}