[PATCH 1/5] objtool: Add '--verbose' option for disassembling affected functions

From: Josh Poimboeuf
Date: Mon Mar 27 2023 - 12:01:46 EST


When a warning is associated with a function, add an option to
disassemble that function.

This makes it easier for reporters to submit the information needed to
diagnose objtool warnings.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
tools/objtool/Documentation/objtool.txt | 5 ++++
tools/objtool/builtin-check.c | 1 +
tools/objtool/include/objtool/builtin.h | 1 +
tools/objtool/include/objtool/warn.h | 38 +++++++++++++++++++++++++
4 files changed, 45 insertions(+)

diff --git a/tools/objtool/Documentation/objtool.txt b/tools/objtool/Documentation/objtool.txt
index 8e53fc6735ef..7c1a46af322f 100644
--- a/tools/objtool/Documentation/objtool.txt
+++ b/tools/objtool/Documentation/objtool.txt
@@ -244,6 +244,11 @@ To achieve the validation, objtool enforces the following rules:
Objtool warnings
----------------

+NOTE: When requesting help with an objtool warning, please re-run the
+kernel build with `OBJTOOL_ARGS="--verbose" make <whatever>` and send
+the full warning output (including any function disassembly below the
+warning) to the objtool maintainers.
+
For asm files, if you're getting an error which doesn't make sense,
first make sure that the affected code follows the above rules.

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 7c175198d09f..b8de42f6778e 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -93,6 +93,7 @@ static const struct option check_options[] = {
OPT_BOOLEAN(0, "no-unreachable", &opts.no_unreachable, "skip 'unreachable instruction' warnings"),
OPT_BOOLEAN(0, "sec-address", &opts.sec_address, "print section addresses in warnings"),
OPT_BOOLEAN(0, "stats", &opts.stats, "print statistics"),
+ OPT_BOOLEAN('v', "verbose", &opts.verbose, "verbose warnings"),

OPT_END(),
};
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index 2a108e648b7a..fcca6662c8b4 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -37,6 +37,7 @@ struct opts {
bool no_unreachable;
bool sec_address;
bool stats;
+ bool verbose;
};

extern struct opts opts;
diff --git a/tools/objtool/include/objtool/warn.h b/tools/objtool/include/objtool/warn.h
index a3e79ae75f2e..b85aa440ee1f 100644
--- a/tools/objtool/include/objtool/warn.h
+++ b/tools/objtool/include/objtool/warn.h
@@ -11,6 +11,7 @@
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
+#include <unistd.h>
#include <objtool/builtin.h>
#include <objtool/elf.h>

@@ -41,6 +42,41 @@ static inline char *offstr(struct section *sec, unsigned long offset)
return str;
}

+static inline void objdump_func(struct section *sec, unsigned long offset)
+{
+ struct symbol *sym = find_func_containing(sec, offset);
+ const char *script_relative = "scripts/objdump-func";
+ bool is_text = (sec->sh.sh_flags & SHF_EXECINSTR);
+ char *cmd, *srctree, *script;
+
+ if (is_text)
+ sym = find_func_containing(sec, offset);
+ if (!sym)
+ sym = find_symbol_containing(sec, offset);
+ if (!sym)
+ return;
+
+ srctree = getenv("abs_srctree");
+ if (!srctree)
+ return;
+
+ script = malloc(strlen(srctree) + strlen(script_relative) + 2);
+ if (!script)
+ return;
+
+ sprintf(script, "%s/%s", srctree, script_relative);
+
+ if (access(script, X_OK))
+ return;
+
+ cmd = malloc(strlen(script) + strlen(objname) + strlen(sym->name) + 10);
+ if (!cmd)
+ return;
+
+ sprintf(cmd, "%s %s %s 1>&2", script, objname, sym->name);
+ system(cmd);
+}
+
#define WARN(format, ...) \
fprintf(stderr, \
"%s: warning: objtool: " format "\n", \
@@ -51,6 +87,8 @@ static inline char *offstr(struct section *sec, unsigned long offset)
char *_str = offstr(sec, offset); \
WARN("%s: " format, _str, ##__VA_ARGS__); \
free(_str); \
+ if (opts.verbose) \
+ objdump_func(sec, offset); \
})

#define BT_FUNC(format, insn, ...) \
--
2.39.2