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Message-Id: <20201013003203.4168817-3-samitolvanen@google.com>
Date: Mon, 12 Oct 2020 17:31:40 -0700
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Masahiro Yamada <masahiroy@...nel.org>, Steven Rostedt <rostedt@...dmis.org>
Cc: Will Deacon <will@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Paul E. McKenney" <paulmck@...nel.org>,
Kees Cook <keescook@...omium.org>, Nick Desaulniers <ndesaulniers@...gle.com>,
clang-built-linux@...glegroups.com, kernel-hardening@...ts.openwall.com,
linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org, x86@...nel.org,
Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH v6 02/25] objtool: Add a pass for generating __mcount_loc
From: Peter Zijlstra <peterz@...radead.org>
Add the --mcount option for generating __mcount_loc sections
needed for dynamic ftrace. Using this pass requires the kernel to
be compiled with -mfentry and CC_USING_NOP_MCOUNT to be defined
in Makefile.
Link: https://lore.kernel.org/lkml/20200625200235.GQ4781@hirez.programming.kicks-ass.net/
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
[Sami: rebased, dropped config changes, fixed to actually use --mcount,
and wrote a commit message.]
Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
tools/objtool/builtin-check.c | 3 +-
tools/objtool/builtin.h | 2 +-
tools/objtool/check.c | 82 +++++++++++++++++++++++++++++++++++
tools/objtool/check.h | 1 +
tools/objtool/objtool.c | 1 +
tools/objtool/objtool.h | 1 +
6 files changed, 88 insertions(+), 2 deletions(-)
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index c6d199bfd0ae..e92e76f69176 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -18,7 +18,7 @@
#include "builtin.h"
#include "objtool.h"
-bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux;
+bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount;
static const char * const check_usage[] = {
"objtool check [<options>] file.o",
@@ -35,6 +35,7 @@ const struct option check_options[] = {
OPT_BOOLEAN('s', "stats", &stats, "print statistics"),
OPT_BOOLEAN('d', "duplicate", &validate_dup, "duplicate validation for vmlinux.o"),
OPT_BOOLEAN('l', "vmlinux", &vmlinux, "vmlinux.o validation"),
+ OPT_BOOLEAN('M', "mcount", &mcount, "generate __mcount_loc"),
OPT_END(),
};
diff --git a/tools/objtool/builtin.h b/tools/objtool/builtin.h
index 85c979caa367..94565a72b701 100644
--- a/tools/objtool/builtin.h
+++ b/tools/objtool/builtin.h
@@ -8,7 +8,7 @@
#include <subcmd/parse-options.h>
extern const struct option check_options[];
-extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux;
+extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount;
extern int cmd_check(int argc, const char **argv);
extern int cmd_orc(int argc, const char **argv);
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index c6ab44543c92..c39c4d2b432a 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -523,6 +523,65 @@ static int create_static_call_sections(struct objtool_file *file)
return 0;
}
+static int create_mcount_loc_sections(struct objtool_file *file)
+{
+ struct section *sec, *reloc_sec;
+ struct reloc *reloc;
+ unsigned long *loc;
+ struct instruction *insn;
+ int idx;
+
+ sec = find_section_by_name(file->elf, "__mcount_loc");
+ if (sec) {
+ INIT_LIST_HEAD(&file->mcount_loc_list);
+ WARN("file already has __mcount_loc section, skipping");
+ return 0;
+ }
+
+ if (list_empty(&file->mcount_loc_list))
+ return 0;
+
+ idx = 0;
+ list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node)
+ idx++;
+
+ sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
+ if (!sec)
+ return -1;
+
+ reloc_sec = elf_create_reloc_section(file->elf, sec, SHT_RELA);
+ if (!reloc_sec)
+ return -1;
+
+ idx = 0;
+ list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node) {
+
+ loc = (unsigned long *)sec->data->d_buf + idx;
+ memset(loc, 0, sizeof(unsigned long));
+
+ reloc = malloc(sizeof(*reloc));
+ if (!reloc) {
+ perror("malloc");
+ return -1;
+ }
+ memset(reloc, 0, sizeof(*reloc));
+
+ reloc->sym = insn->sec->sym;
+ reloc->addend = insn->offset;
+ reloc->type = R_X86_64_64;
+ reloc->offset = idx * sizeof(unsigned long);
+ reloc->sec = reloc_sec;
+ elf_add_reloc(file->elf, reloc);
+
+ idx++;
+ }
+
+ if (elf_rebuild_reloc_section(file->elf, reloc_sec))
+ return -1;
+
+ return 0;
+}
+
/*
* Warnings shouldn't be reported for ignored functions.
*/
@@ -949,6 +1008,22 @@ static int add_call_destinations(struct objtool_file *file)
insn->type = INSN_NOP;
}
+ if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) {
+ if (reloc) {
+ reloc->type = R_NONE;
+ elf_write_reloc(file->elf, reloc);
+ }
+
+ elf_write_insn(file->elf, insn->sec,
+ insn->offset, insn->len,
+ arch_nop_insn(insn->len));
+
+ insn->type = INSN_NOP;
+
+ list_add_tail(&insn->mcount_loc_node,
+ &file->mcount_loc_list);
+ }
+
/*
* Whatever stack impact regular CALLs have, should be undone
* by the RETURN of the called function.
@@ -2920,6 +2995,13 @@ int check(struct objtool_file *file)
goto out;
warnings += ret;
+ if (mcount) {
+ ret = create_mcount_loc_sections(file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
+ }
+
out:
if (ret < 0) {
/*
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index 5ec00a4b891b..070baec2050a 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -23,6 +23,7 @@ struct instruction {
struct list_head list;
struct hlist_node hash;
struct list_head static_call_node;
+ struct list_head mcount_loc_node;
struct section *sec;
unsigned long offset;
unsigned int len;
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index 9df0cd86d310..c1819a6f2a18 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -62,6 +62,7 @@ struct objtool_file *objtool_open_read(const char *_objname)
INIT_LIST_HEAD(&file.insn_list);
hash_init(file.insn_hash);
INIT_LIST_HEAD(&file.static_call_list);
+ INIT_LIST_HEAD(&file.mcount_loc_list);
file.c_file = !vmlinux && find_section_by_name(file.elf, ".comment");
file.ignore_unreachables = no_unreachable;
file.hints = false;
diff --git a/tools/objtool/objtool.h b/tools/objtool/objtool.h
index 4125d4578b23..cf004dd60c2b 100644
--- a/tools/objtool/objtool.h
+++ b/tools/objtool/objtool.h
@@ -19,6 +19,7 @@ struct objtool_file {
struct list_head insn_list;
DECLARE_HASHTABLE(insn_hash, 20);
struct list_head static_call_list;
+ struct list_head mcount_loc_list;
bool ignore_unreachables, c_file, hints, rodata;
};
--
2.28.0.1011.ga647a8990f-goog
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