objtool: Add base objtool support for livepatch modules

In preparation for klp-build, enable "classic" objtool to work on
livepatch modules:

  - Avoid duplicate symbol/section warnings for prefix symbols and the
    .static_call_sites and __mcount_loc sections which may have already
    been extracted by klp diff.

  - Add __klp_funcs to the IBT function pointer section whitelist.

  - Prevent KLP symbols from getting incorrectly classified as cold
    subfunctions.

Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index b2659fbf7bc955b522b30a28b226519eaede9176..d071fbf73e4c0ceb8237188668ccd32a5701c066 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3,6 +3,7 @@
  * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
  */
 
+#define _GNU_SOURCE /* memmem() */
 #include <string.h>
 #include <stdlib.h>
 #include <inttypes.h>
@@ -611,6 +612,20 @@ static int init_pv_ops(struct objtool_file *file)
        return 0;
 }
 
+static bool is_livepatch_module(struct objtool_file *file)
+{
+       struct section *sec;
+
+       if (!opts.module)
+               return false;
+
+       sec = find_section_by_name(file->elf, ".modinfo");
+       if (!sec)
+               return false;
+
+       return memmem(sec->data->d_buf, sec_size(sec), "\0livepatch=Y", 12);
+}
+
 static int create_static_call_sections(struct objtool_file *file)
 {
        struct static_call_site *site;
@@ -622,7 +637,14 @@ static int create_static_call_sections(struct objtool_file *file)
 
        sec = find_section_by_name(file->elf, ".static_call_sites");
        if (sec) {
-               WARN("file already has .static_call_sites section, skipping");
+               /*
+                * Livepatch modules may have already extracted the static call
+                * site entries to take advantage of vmlinux static call
+                * privileges.
+                */
+               if (!file->klp)
+                       WARN("file already has .static_call_sites section, skipping");
+
                return 0;
        }
 
@@ -666,7 +688,7 @@ static int create_static_call_sections(struct objtool_file *file)
 
                key_sym = find_symbol_by_name(file->elf, tmp);
                if (!key_sym) {
-                       if (!opts.module) {
+                       if (!opts.module || file->klp) {
                                ERROR("static_call: can't find static_call_key symbol: %s", tmp);
                                return -1;
                        }
@@ -885,7 +907,13 @@ static int create_mcount_loc_sections(struct objtool_file *file)
 
        sec = find_section_by_name(file->elf, "__mcount_loc");
        if (sec) {
-               WARN("file already has __mcount_loc section, skipping");
+               /*
+                * Livepatch modules have already extracted their __mcount_loc
+                * entries to cover the !CONFIG_FTRACE_MCOUNT_USE_OBJTOOL case.
+                */
+               if (!file->klp)
+                       WARN("file already has __mcount_loc section, skipping");
+
                return 0;
        }
 
@@ -2569,6 +2597,8 @@ static bool validate_branch_enabled(void)
 
 static int decode_sections(struct objtool_file *file)
 {
+       file->klp = is_livepatch_module(file);
+
        mark_rodata(file);
 
        if (init_pv_ops(file))
@@ -4244,6 +4274,9 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
  *   - compiler cloned functions (*.cold, *.part0, etc)
  *   - asm functions created with inline asm or without SYM_FUNC_START()
  *
+ * Also, the function may already have a prefix from a previous objtool run
+ * (livepatch extracted functions, or manually running objtool multiple times).
+ *
  * So return 0 if the NOPs are missing or the function already has a prefix
  * symbol.
  */
@@ -4266,6 +4299,14 @@ static int create_prefix_symbol(struct objtool_file *file, struct symbol *func)
        if (snprintf_check(name, SYM_NAME_LEN, "__pfx_%s", func->name))
                return -1;
 
+       if (file->klp) {
+               struct symbol *pfx;
+
+               pfx = find_symbol_by_offset(func->sec, func->offset - opts.prefix);
+               if (pfx && is_prefix_func(pfx) && !strcmp(pfx->name, name))
+                       return 0;
+       }
+
        insn = find_insn(file, func->sec, func->offset);
        if (!insn) {
                WARN("%s: can't find starting instruction", func->name);
@@ -4618,6 +4659,7 @@ static int validate_ibt(struct objtool_file *file)
                    !strncmp(sec->name, ".debug", 6)                    ||
                    !strcmp(sec->name, ".altinstructions")              ||
                    !strcmp(sec->name, ".ibt_endbr_seal")               ||
+                   !strcmp(sec->name, ".kcfi_traps")                   ||
                    !strcmp(sec->name, ".orc_unwind_ip")                ||
                    !strcmp(sec->name, ".retpoline_sites")              ||
                    !strcmp(sec->name, ".smp_locks")                    ||
@@ -4627,12 +4669,12 @@ static int validate_ibt(struct objtool_file *file)
                    !strcmp(sec->name, "__bug_table")                   ||
                    !strcmp(sec->name, "__ex_table")                    ||
                    !strcmp(sec->name, "__jump_table")                  ||
+                   !strcmp(sec->name, "__klp_funcs")                   ||
                    !strcmp(sec->name, "__mcount_loc")                  ||
-                   !strcmp(sec->name, ".kcfi_traps")                   ||
                    !strcmp(sec->name, ".llvm.call-graph-profile")      ||
                    !strcmp(sec->name, ".llvm_bb_addr_map")             ||
                    !strcmp(sec->name, "__tracepoints")                 ||
-                   strstr(sec->name, "__patchable_function_entries"))
+                   !strcmp(sec->name, "__patchable_function_entries"))
                        continue;
 
                for_each_reloc(sec->rsec, reloc)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 4bb7ce994b6a76ef5ea6dc62345be70441cdcbb4..5feeefc7fc8f80e9e28bb0163d6b4925de67f2b6 100644 (file)
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -499,7 +499,10 @@ static int elf_add_symbol(struct elf *elf, struct symbol *sym)
             strstarts(sym->name, "__pi___cfi_")))
                sym->prefix = 1;
 
-       if (is_func_sym(sym) && strstr(sym->name, ".cold"))
+       if (strstarts(sym->name, ".klp.sym"))
+               sym->klp = 1;
+
+       if (!sym->klp && is_func_sym(sym) && strstr(sym->name, ".cold"))
                sym->cold = 1;
        sym->pfunc = sym->cfunc = sym;
 

diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index 60f844e43c5a2602e85fb67ba7277158d24df9ad..21d8b825fd8f066d82df1582bdcb46c7300f2435 100644 (file)
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -88,6 +88,7 @@ struct symbol {
        u8 debug_checksum    : 1;
        u8 changed           : 1;
        u8 included          : 1;
+       u8 klp               : 1;
        struct list_head pv_target;
        struct reloc *relocs;
        struct section *group_sec;

diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index 7f70b41d1b8dbd4ea1998baf63700a74e9fa30da..f7051bbe0bcb265471a30a967ed6e1d88970c702 100644 (file)
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -28,7 +28,7 @@ struct objtool_file {
        struct list_head mcount_loc_list;
        struct list_head endbr_list;
        struct list_head call_list;
-       bool ignore_unreachables, hints, rodata;
+       bool ignore_unreachables, hints, rodata, klp;
 
        unsigned int nr_endbr;
        unsigned int nr_endbr_int;