[ARM] 5384/1: unwind: Add stack unwinding support for loadable modules

This patch adds ELF section parsing for the unwinding tables in loadable
modules together with the PREL31 relocation symbol resolving.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 82 insertions, 5 deletions

diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
index a58378c343b..def8eac6e89 100644
--- a/arch/arm/include/asm/elf.h
+++ b/arch/arm/include/asm/elf.h
@@ -50,6 +50,7 @@ typedef struct user_fp elf_fpregset_t;
 #define R_ARM_ABS32     2
 #define R_ARM_CALL      28
 #define R_ARM_JUMP24    29
+#define R_ARM_PREL31    42
 
 /*
  * These are used to set parameters in the core dumps.
diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h
index 24b168dc31a..e4dfa69abb6 100644
--- a/arch/arm/include/asm/module.h
+++ b/arch/arm/include/asm/module.h
@@ -1,15 +1,27 @@
 #ifndef _ASM_ARM_MODULE_H
 #define _ASM_ARM_MODULE_H
 
-struct mod_arch_specific
-{
-        int foo;
-};
-
 #define Elf_Shdr        Elf32_Shdr
 #define Elf_Sym         Elf32_Sym
 #define Elf_Ehdr        Elf32_Ehdr
 
+struct unwind_table;
+
+struct mod_arch_specific
+{
+#ifdef CONFIG_ARM_UNWIND
+        Elf_Shdr *unw_sec_init;
+        Elf_Shdr *unw_sec_devinit;
+        Elf_Shdr *unw_sec_core;
+        Elf_Shdr *sec_init_text;
+        Elf_Shdr *sec_devinit_text;
+        Elf_Shdr *sec_core_text;
+        struct unwind_table *unwind_init;
+        struct unwind_table *unwind_devinit;
+        struct unwind_table *unwind_core;
+#endif
+};
+
 /*
  * Include the ARM architecture version.
  */
diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index dab48f27263..13dbd5bf5cc 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -22,6 +22,7 @@
 
 #include <asm/pgtable.h>
 #include <asm/sections.h>
+#include <asm/unwind.h>
 
 #ifdef CONFIG_XIP_KERNEL
 /*
@@ -66,6 +67,24 @@ int module_frob_arch_sections(Elf_Ehdr *hdr,
                               char *secstrings,
                               struct module *mod)
 {
+#ifdef CONFIG_ARM_UNWIND
+        Elf_Shdr *s, *sechdrs_end = sechdrs + hdr->e_shnum;
+
+        for (s = sechdrs; s < sechdrs_end; s++) {
+                if (strcmp(".ARM.exidx.init.text", secstrings + s->sh_name) == 0)
+                        mod->arch.unw_sec_init = s;
+                else if (strcmp(".ARM.exidx.devinit.text", secstrings + s->sh_name) == 0)
+                        mod->arch.unw_sec_devinit = s;
+                else if (strcmp(".ARM.exidx", secstrings + s->sh_name) == 0)
+                        mod->arch.unw_sec_core = s;
+                else if (strcmp(".init.text", secstrings + s->sh_name) == 0)
+                        mod->arch.sec_init_text = s;
+                else if (strcmp(".devinit.text", secstrings + s->sh_name) == 0)
+                        mod->arch.sec_devinit_text = s;
+                else if (strcmp(".text", secstrings + s->sh_name) == 0)
+                        mod->arch.sec_core_text = s;
+        }
+#endif
         return 0;
 }
 
@@ -104,6 +123,10 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
                 loc = dstsec->sh_addr + rel->r_offset;
 
                 switch (ELF32_R_TYPE(rel->r_info)) {
+                case R_ARM_NONE:
+                        /* ignore */
+                        break;
+
                 case R_ARM_ABS32:
                         *(u32 *)loc += sym->st_value;
                         break;
@@ -132,6 +155,11 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
                         *(u32 *)loc |= offset & 0x00ffffff;
                         break;
 
+                case R_ARM_PREL31:
+                        offset = *(u32 *)loc + sym->st_value - loc;
+                        *(u32 *)loc = offset & 0x7fffffff;
+                        break;
+
                 default:
                         printk(KERN_ERR "%s: unknown relocation: %u\n",
                                module->name, ELF32_R_TYPE(rel->r_info));
@@ -150,14 +178,50 @@ apply_relocate_add(Elf32_Shdr *sechdrs, const char *strtab,
         return -ENOEXEC;
 }
 
+#ifdef CONFIG_ARM_UNWIND
+static void register_unwind_tables(struct module *mod)
+{
+        if (mod->arch.unw_sec_init && mod->arch.sec_init_text)
+                mod->arch.unwind_init =
+                        unwind_table_add(mod->arch.unw_sec_init->sh_addr,
+                                         mod->arch.unw_sec_init->sh_size,
+                                         mod->arch.sec_init_text->sh_addr,
+                                         mod->arch.sec_init_text->sh_size);
+        if (mod->arch.unw_sec_devinit && mod->arch.sec_devinit_text)
+                mod->arch.unwind_devinit =
+                        unwind_table_add(mod->arch.unw_sec_devinit->sh_addr,
+                                         mod->arch.unw_sec_devinit->sh_size,
+                                         mod->arch.sec_devinit_text->sh_addr,
+                                         mod->arch.sec_devinit_text->sh_size);
+        if (mod->arch.unw_sec_core && mod->arch.sec_core_text)
+                mod->arch.unwind_core =
+                        unwind_table_add(mod->arch.unw_sec_core->sh_addr,
+                                         mod->arch.unw_sec_core->sh_size,
+                                         mod->arch.sec_core_text->sh_addr,
+                                         mod->arch.sec_core_text->sh_size);
+}
+
+static void unregister_unwind_tables(struct module *mod)
+{
+        unwind_table_del(mod->arch.unwind_init);
+        unwind_table_del(mod->arch.unwind_devinit);
+        unwind_table_del(mod->arch.unwind_core);
+}
+#else
+static inline void register_unwind_tables(struct module *mod) { }
+static inline void unregister_unwind_tables(struct module *mod) { }
+#endif
+
 int
 module_finalize(const Elf32_Ehdr *hdr, const Elf_Shdr *sechdrs,
                 struct module *module)
 {
+        register_unwind_tables(module);
         return 0;
 }
 
 void
 module_arch_cleanup(struct module *mod)
 {
+        unregister_unwind_tables(mod);
 }