Hello Ard!

On 09/03/18 09:50, Ard Biesheuvel wrote:

quoted

+static u32 fixed_plts[] = {
+       FTRACE_ADDR,
+       MCOUNT_ADDR,
+#ifdef CONFIG_OLD_MCOUNT
+       (unsigned long)ftrace_caller_old,
+       (unsigned long)mcount,
+#endif
+};
+

Do we need this stuff in the PLT loader if ftrace is disabled?

You are right, it probably would not even build w/o FTRACE.
I'll fix it, thanks for looking into this!

quoted

 static bool in_init(const struct module *mod, unsigned long loc)
 {
        return loc - (u32)mod->init_layout.base < mod->init_layout.size;

@@ -31,26 +41,43 @@ u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
 {
        struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core :
                                                          &mod->arch.init;
+       int idx;
+       struct plt_entries *plt;
+
+       /* Pre-allocate entries in the first plt */
+       if (!pltsec->plt_count) {
+               plt = (struct plt_entries *)pltsec->plt->sh_addr;
+               for (idx = 0; idx < ARRAY_SIZE(plt->ldr); ++idx)
+                       plt->ldr[idx] = PLT_ENT_LDR;
+               memcpy(plt->lit, fixed_plts, sizeof(fixed_plts));
+               pltsec->plt_count = ARRAY_SIZE(fixed_plts);
+               /*
+                * cache the address,
+                * ELF header is available only during module load
+                */
+               pltsec->plt_ent = plt;
+       }
+       plt = pltsec->plt_ent;

-       struct plt_entries *plt = (struct plt_entries *)pltsec->plt->sh_addr;
-       int idx = 0;
+       idx = ARRAY_SIZE(fixed_plts);
+       while (idx)
+               if (plt->lit[--idx] == val)
+                       return (u32)&plt->ldr[idx];

Same here.

-- 
Best regards,
Alexander Sverdlin.