powerpc/module: Only try to generate the ftrace_caller() stub once

Currently we generate the module stub for ftrace_caller() at the bottom
of apply_relocate_add(). However apply_relocate_add() is potentially
called more than once per module, which means we will try to generate
the ftrace_caller() stub multiple times.

Although the current code deals with that correctly, ie. it only
generates a stub the first time, it would be clearer to only try to
generate the stub once.

Note also on first reading it may appear that we generate a different
stub for each section that requires relocation, but that is not the
case. The code in stub_for_addr() that searches for an existing stub
uses sechdrs[me->arch.stubs_section], ie. the single stub section for
this module.

A cleaner approach is to only generate the ftrace_caller() stub once,
from module_finalize(). Although the original code didn't check to see
if the stub was actually generated correctly, it seems prudent to add a
check, so do that. And an additional benefit is we can clean the ifdefs
up a little.

Finally we must propagate the const'ness of some of the pointers passed
to module_finalize(), but that is also an improvement.

Reviewed-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
index dcfcad139bccc0765e3dc6a5f17cd5566258910b..74d25a749018595dab69c9e91cb4541e5b45f279 100644 (file)
--- a/arch/powerpc/include/asm/module.h
+++ b/arch/powerpc/include/asm/module.h
@@ -82,6 +82,15 @@ bool is_module_trampoline(u32 *insns);
 int module_trampoline_target(struct module *mod, u32 *trampoline,
                             unsigned long *target);
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs);
+#else
+static inline int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
+{
+       return 0;
+}
+#endif
+
 struct exception_table_entry;
 void sort_ex_table(struct exception_table_entry *start,
                   struct exception_table_entry *finish);

diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index 9547381b631a587b6d520b22f414039d6d458525..d1f1b35bf0c72b098b45c83e9cbf3480db03f01e 100644 (file)
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c
@@ -47,6 +47,11 @@ int module_finalize(const Elf_Ehdr *hdr,
                const Elf_Shdr *sechdrs, struct module *me)
 {
        const Elf_Shdr *sect;
+       int rc;
+
+       rc = module_finalize_ftrace(me, sechdrs);
+       if (rc)
+               return rc;
 
        /* Apply feature fixups */
        sect = find_section(hdr, sechdrs, "__ftr_fixup");

diff --git a/arch/powerpc/kernel/module_32.c b/arch/powerpc/kernel/module_32.c
index 2c01665eb410afe448eb15c533da1af921af331d..5a7a78f12562969d8db892d4ab63be131530e62e 100644 (file)
--- a/arch/powerpc/kernel/module_32.c
+++ b/arch/powerpc/kernel/module_32.c
@@ -181,7 +181,7 @@ static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 /* Set up a trampoline in the PLT to bounce us to the distant function */
 static uint32_t do_plt_call(void *location,
                            Elf32_Addr val,
-                           Elf32_Shdr *sechdrs,
+                           const Elf32_Shdr *sechdrs,
                            struct module *mod)
 {
        struct ppc_plt_entry *entry;
@@ -294,11 +294,19 @@ int apply_relocate_add(Elf32_Shdr *sechdrs,
                        return -ENOEXEC;
                }
        }
+
+       return 0;
+}
+
 #ifdef CONFIG_DYNAMIC_FTRACE
-       module->arch.tramp =
-               do_plt_call(module->core_layout.base,
-                           (unsigned long)ftrace_caller,
-                           sechdrs, module);
-#endif
+int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
+{
+       module->arch.tramp = do_plt_call(module->core_layout.base,
+                                        (unsigned long)ftrace_caller,
+                                        sechdrs, module);
+       if (!module->arch.tramp)
+               return -ENOENT;
+
        return 0;
 }
+#endif

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index ac64ffdb52c848d170fa34ef9ffe50d8db4d19c0..599c753c79606c046566a4f902d153f6f721d577 100644 (file)
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -413,7 +413,7 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr,
 /* r2 is the TOC pointer: it actually points 0x8000 into the TOC (this
    gives the value maximum span in an instruction which uses a signed
    offset) */
-static inline unsigned long my_r2(Elf64_Shdr *sechdrs, struct module *me)
+static inline unsigned long my_r2(const Elf64_Shdr *sechdrs, struct module *me)
 {
        return sechdrs[me->arch.toc_section].sh_addr + 0x8000;
 }
@@ -426,7 +426,7 @@ static inline unsigned long my_r2(Elf64_Shdr *sechdrs, struct module *me)
 #define PPC_HA(v) PPC_HI ((v) + 0x8000)
 
 /* Patch stub to reference function and correct r2 value. */
-static inline int create_stub(Elf64_Shdr *sechdrs,
+static inline int create_stub(const Elf64_Shdr *sechdrs,
                              struct ppc64_stub_entry *entry,
                              unsigned long addr,
                              struct module *me)
@@ -452,7 +452,7 @@ static inline int create_stub(Elf64_Shdr *sechdrs,
 
 /* Create stub to jump to function described in this OPD/ptr: we need the
    stub to set up the TOC ptr (r2) for the function. */
-static unsigned long stub_for_addr(Elf64_Shdr *sechdrs,
+static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs,
                                   unsigned long addr,
                                   struct module *me)
 {
@@ -693,12 +693,18 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
                }
        }
 
+       return 0;
+}
+
 #ifdef CONFIG_DYNAMIC_FTRACE
-       me->arch.toc = my_r2(sechdrs, me);
-       me->arch.tramp = stub_for_addr(sechdrs,
-                                      (unsigned long)ftrace_caller,
-                                      me);
-#endif
+int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
+{
+       mod->arch.toc = my_r2(sechdrs, mod);
+       mod->arch.tramp = stub_for_addr(sechdrs, (unsigned long)ftrace_caller, mod);
+
+       if (!mod->arch.tramp)
+               return -ENOENT;
 
        return 0;
 }
+#endif