objtool executes the objdump command to disassemble code. Use libopcodes
instead to have more control about the disassembly scope and output.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
---
tools/objtool/Makefile | 2 +-
tools/objtool/arch/loongarch/decode.c | 6 +
tools/objtool/arch/powerpc/decode.c | 6 +
tools/objtool/arch/x86/decode.c | 7 +
tools/objtool/check.c | 4 +-
tools/objtool/disas.c | 186 +++++++++++++++---------
tools/objtool/include/objtool/arch.h | 5 +
tools/objtool/include/objtool/check.h | 5 +
tools/objtool/include/objtool/objtool.h | 4 +
9 files changed, 154 insertions(+), 71 deletions(-)
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 8c20361dd100..00350fc7c662 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -34,7 +34,7 @@ INCLUDES := -I$(srctree)/tools/include \
# is passed here to match a legacy behavior.
WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed -Wno-nested-externs
OBJTOOL_CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS)
-OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS)
+OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS) -lopcodes
# Allow old libelf to be used:
elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(HOSTCC) $(OBJTOOL_CFLAGS) -x c -E - 2>/dev/null | grep elf_getshdr)
diff --git a/tools/objtool/arch/loongarch/decode.c b/tools/objtool/arch/loongarch/decode.c
index b6fdc68053cc..bf5ac6750512 100644
--- a/tools/objtool/arch/loongarch/decode.c
+++ b/tools/objtool/arch/loongarch/decode.c
@@ -386,4 +386,10 @@ unsigned long arch_jump_table_sym_offset(struct reloc *reloc, struct reloc *tabl
default:
return reloc->sym->offset + reloc_addend(reloc);
}
+
+int arch_disas_info_init(struct disassemble_info *dinfo)
+{
+ return disas_info_init(dinfo, bfd_arch_loongarch,
+ bfd_mach_loongarch32, bfd_mach_loongarch64,
+ NULL);
}
diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
index c851c51d4bd3..c0fcab2d643c 100644
--- a/tools/objtool/arch/powerpc/decode.c
+++ b/tools/objtool/arch/powerpc/decode.c
@@ -127,4 +127,10 @@ unsigned int arch_reloc_size(struct reloc *reloc)
default:
return 8;
}
+
+int arch_disas_info_init(struct disassemble_info *dinfo)
+{
+ return disas_info_init(dinfo, bfd_arch_powerpc,
+ bfd_mach_ppc, bfd_mach_ppc64,
+ NULL);
}
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 98c4713c1b09..6c13c67ed9b9 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -880,3 +880,10 @@ unsigned int arch_reloc_size(struct reloc *reloc)
return 8;
}
}
+
+int arch_disas_info_init(struct disassemble_info *dinfo)
+{
+ return disas_info_init(dinfo, bfd_arch_i386,
+ bfd_mach_i386_i386, bfd_mach_x86_64,
+ "att");
+}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 085fcc1b643b..9cfac23185b8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4701,8 +4701,6 @@ int check(struct objtool_file *file)
goto out;
}
- free_insns(file);
-
if (opts.stats) {
printf("nr_insns_visited: %ld\n", nr_insns_visited);
printf("nr_cfi: %ld\n", nr_cfi);
@@ -4726,5 +4724,7 @@ int check(struct objtool_file *file)
disas_context_destroy(disas_ctx);
}
+ free_insns(file);
+
return ret;
}
diff --git a/tools/objtool/disas.c b/tools/objtool/disas.c
index ed74554bccbf..f2eb1050ce11 100644
--- a/tools/objtool/disas.c
+++ b/tools/objtool/disas.c
@@ -4,17 +4,52 @@
*/
#include <objtool/arch.h>
+#include <objtool/check.h>
#include <objtool/warn.h>
+#include <bfd.h>
#include <linux/string.h>
+#include <tools/dis-asm-compat.h>
struct disas_context {
struct objtool_file *file;
+ disassembler_ftype disassembler;
+ struct disassemble_info info;
};
+/*
+ * Initialize disassemble info arch, mach (32 or 64-bit) and options.
+ */
+int disas_info_init(struct disassemble_info *dinfo,
+ int arch, int mach32, int mach64,
+ const char *options)
+{
+ struct disas_context *dctx = dinfo->application_data;
+ struct objtool_file *file = dctx->file;
+
+ dinfo->arch = arch;
+
+ switch (file->elf->ehdr.e_ident[EI_CLASS]) {
+ case ELFCLASS32:
+ dinfo->mach = mach32;
+ break;
+ case ELFCLASS64:
+ dinfo->mach = mach64;
+ break;
+ default:
+ return -1;
+ }
+
+ dinfo->disassembler_options = options;
+
+ return 0;
+}
+
struct disas_context *disas_context_create(struct objtool_file *file)
{
struct disas_context *dctx;
+ struct disassemble_info *dinfo;
+ int err;
dctx = malloc(sizeof(*dctx));
if (!dctx) {
@@ -23,8 +58,49 @@ struct disas_context *disas_context_create(struct objtool_file *file)
}
dctx->file = file;
+ dinfo = &dctx->info;
+
+ init_disassemble_info_compat(dinfo, stdout,
+ (fprintf_ftype)fprintf,
+ fprintf_styled);
+
+ dinfo->read_memory_func = buffer_read_memory;
+ dinfo->application_data = dctx;
+
+ /*
+ * bfd_openr() is not used to avoid doing ELF data processing
+ * and caching that has already being done. Here, we just need
+ * to identify the target file so we call an arch specific
+ * function to fill some disassemble info (arch, mach).
+ */
+
+ dinfo->arch = bfd_arch_unknown;
+ dinfo->mach = 0;
+
+ err = arch_disas_info_init(dinfo);
+ if (err || dinfo->arch == bfd_arch_unknown || dinfo->mach == 0) {
+ WARN("failed to init disassembly arch\n");
+ goto error;
+ }
+
+ dinfo->endian = (file->elf->ehdr.e_ident[EI_DATA] == ELFDATA2MSB) ?
+ BFD_ENDIAN_BIG : BFD_ENDIAN_LITTLE;
+
+ disassemble_init_for_target(dinfo);
+
+ dctx->disassembler = disassembler(dinfo->arch,
+ dinfo->endian == BFD_ENDIAN_BIG,
+ dinfo->mach, NULL);
+ if (!dctx->disassembler) {
+ WARN("failed to create disassembler function\n");
+ goto error;
+ }
return dctx;
+
+error:
+ free(dctx);
+ return NULL;
}
void disas_context_destroy(struct disas_context *dctx)
@@ -32,60 +108,54 @@ void disas_context_destroy(struct disas_context *dctx)
free(dctx);
}
-/* 'funcs' is a space-separated list of function names */
-static void disas_funcs(const char *funcs)
+/*
+ * Disassemble a single instruction. Return the size of the instruction.
+ */
+static size_t disas_insn(struct disas_context *dctx,
+ struct instruction *insn)
{
- const char *objdump_str, *cross_compile;
- int size, ret;
- char *cmd;
-
- cross_compile = getenv("CROSS_COMPILE");
- if (!cross_compile)
- cross_compile = "";
-
- objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
- "BEGIN { split(_funcs, funcs); }"
- "/^$/ { func_match = 0; }"
- "/<.*>:/ { "
- "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
- "for (i in funcs) {"
- "if (funcs[i] == f) {"
- "func_match = 1;"
- "base = strtonum(\"0x\" $1);"
- "break;"
- "}"
- "}"
- "}"
- "{"
- "if (func_match) {"
- "addr = strtonum(\"0x\" $1);"
- "printf(\"%%04x \", addr - base);"
- "print;"
- "}"
- "}' 1>&2";
-
- /* fake snprintf() to calculate the size */
- size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
- if (size <= 0) {
- WARN("objdump string size calculation failed");
- return;
- }
-
- cmd = malloc(size);
+ disassembler_ftype disasm = dctx->disassembler;
+ struct disassemble_info *dinfo = &dctx->info;
+
+ /*
+ * Set the disassembler buffer to read data from the section
+ * containing the instruction to disassemble.
+ */
+ dinfo->buffer = insn->sec->data->d_buf;
+ dinfo->buffer_vma = 0;
+ dinfo->buffer_length = insn->sec->sh.sh_size;
+
+ return disasm(insn->offset, &dctx->info);
+}
- /* real snprintf() */
- snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
- ret = system(cmd);
- if (ret) {
- WARN("disassembly failed: %d", ret);
- return;
+/*
+ * Disassemble a function.
+ */
+static void disas_func(struct disas_context *dctx, struct symbol *func)
+{
+ struct instruction *insn;
+ size_t addr, size;
+
+ printf("%s:\n", func->name);
+ sym_for_each_insn(dctx->file, func, insn) {
+
+ addr = insn->offset;
+ printf(" %6lx: %s+0x%-6lx ",
+ addr, func->name, addr - func->offset);
+ size = disas_insn(dctx, insn);
+ printf("\n");
+ if (size != insn->len)
+ WARN("inconsistent insn size (%ld and %d)\n", size, insn->len);
}
+ printf("\n");
}
+/*
+ * Disassemble all warned functions.
+ */
void disas_warned_funcs(struct disas_context *dctx)
{
struct symbol *sym;
- char *funcs = NULL, *tmp;
if (!dctx) {
ERROR("disassembly context is not defined");
@@ -93,27 +163,7 @@ void disas_warned_funcs(struct disas_context *dctx)
}
for_each_sym(dctx->file, sym) {
- if (sym->warned) {
- if (!funcs) {
- funcs = malloc(strlen(sym->name) + 1);
- if (!funcs) {
- ERROR_GLIBC("malloc");
- return;
- }
- strcpy(funcs, sym->name);
- } else {
- tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
- if (!tmp) {
- ERROR_GLIBC("malloc");
- return;
- }
- sprintf(tmp, "%s %s", funcs, sym->name);
- free(funcs);
- funcs = tmp;
- }
- }
+ if (sym->warned)
+ disas_func(dctx, sym);
}
-
- if (funcs)
- disas_funcs(funcs);
}
diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h
index 01ef6f415adf..aecf8fc29571 100644
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -6,6 +6,8 @@
#ifndef _ARCH_H
#define _ARCH_H
+#include <bfd.h>
+#include <dis-asm.h>
#include <stdbool.h>
#include <linux/list.h>
#include <objtool/objtool.h>
@@ -98,7 +100,10 @@ int arch_rewrite_retpolines(struct objtool_file *file);
bool arch_pc_relative_reloc(struct reloc *reloc);
+
unsigned int arch_reloc_size(struct reloc *reloc);
unsigned long arch_jump_table_sym_offset(struct reloc *reloc, struct reloc *table);
+int arch_disas_info_init(struct disassemble_info *dinfo);
+
#endif /* _ARCH_H */
diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index 00fb745e7233..5290ac1ebbc1 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -125,4 +125,9 @@ struct instruction *next_insn_same_sec(struct objtool_file *file, struct instruc
insn && insn->sec == _sec; \
insn = next_insn_same_sec(file, insn))
+#define sym_for_each_insn(file, sym, insn) \
+ for (insn = find_insn(file, sym->sec, sym->offset); \
+ insn && insn->offset < sym->offset + sym->len; \
+ insn = next_insn_same_sec(file, insn))
+
#endif /* _CHECK_H */
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index f5ab71f07f5c..0b404cfd81c0 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -48,8 +48,12 @@ int orc_dump(const char *objname);
int orc_create(struct objtool_file *file);
struct disas_context;
+struct disassemble_info;
struct disas_context *disas_context_create(struct objtool_file *file);
void disas_context_destroy(struct disas_context *dctx);
void disas_warned_funcs(struct disas_context *dctx);
+int disas_info_init(struct disassemble_info *dinfo,
+ int arch, int mach32, int mach64,
+ const char *options);
#endif /* _OBJTOOL_H */
--
2.43.5On Fri, Jun 06, 2025 at 05:34:30PM +0200, Alexandre Chartre wrote: > objtool executes the objdump command to disassemble code. Use libopcodes > instead to have more control about the disassembly scope and output. > > Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> > --- > tools/objtool/Makefile | 2 +- > tools/objtool/arch/loongarch/decode.c | 6 + > tools/objtool/arch/powerpc/decode.c | 6 + > tools/objtool/arch/x86/decode.c | 7 + > tools/objtool/check.c | 4 +- > tools/objtool/disas.c | 186 +++++++++++++++--------- > tools/objtool/include/objtool/arch.h | 5 + > tools/objtool/include/objtool/check.h | 5 + > tools/objtool/include/objtool/objtool.h | 4 + > 9 files changed, 154 insertions(+), 71 deletions(-) > > diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile > index 8c20361dd100..00350fc7c662 100644 > --- a/tools/objtool/Makefile > +++ b/tools/objtool/Makefile > @@ -34,7 +34,7 @@ INCLUDES := -I$(srctree)/tools/include \ > # is passed here to match a legacy behavior. > WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed -Wno-nested-externs > OBJTOOL_CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS) > -OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS) > +OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS) -lopcodes Would it be possible to make this optional? Such that when people do not have libopcodes installed they can still build the kernel. Or is libopcodes a mandatory part of any binutils installation?
On 6/11/25 14:23, Peter Zijlstra wrote: > On Fri, Jun 06, 2025 at 05:34:30PM +0200, Alexandre Chartre wrote: >> objtool executes the objdump command to disassemble code. Use libopcodes >> instead to have more control about the disassembly scope and output. >> >> Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> >> --- >> tools/objtool/Makefile | 2 +- >> tools/objtool/arch/loongarch/decode.c | 6 + >> tools/objtool/arch/powerpc/decode.c | 6 + >> tools/objtool/arch/x86/decode.c | 7 + >> tools/objtool/check.c | 4 +- >> tools/objtool/disas.c | 186 +++++++++++++++--------- >> tools/objtool/include/objtool/arch.h | 5 + >> tools/objtool/include/objtool/check.h | 5 + >> tools/objtool/include/objtool/objtool.h | 4 + >> 9 files changed, 154 insertions(+), 71 deletions(-) >> >> diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile >> index 8c20361dd100..00350fc7c662 100644 >> --- a/tools/objtool/Makefile >> +++ b/tools/objtool/Makefile >> @@ -34,7 +34,7 @@ INCLUDES := -I$(srctree)/tools/include \ >> # is passed here to match a legacy behavior. >> WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed -Wno-nested-externs >> OBJTOOL_CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS) >> -OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS) >> +OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS) -lopcodes > > Would it be possible to make this optional? Such that when people do not > have libopcodes installed they can still build the kernel. > > Or is libopcodes a mandatory part of any binutils installation? I guess that libopcodes is mandatory because it is used by as (and also objdump). But I can check if it is effectively present anyway. alex.
On Wed, Jun 11, 2025 at 03:35:38PM +0200, Alexandre Chartre wrote: > > On 6/11/25 14:23, Peter Zijlstra wrote: > > On Fri, Jun 06, 2025 at 05:34:30PM +0200, Alexandre Chartre wrote: > > > objtool executes the objdump command to disassemble code. Use libopcodes > > > instead to have more control about the disassembly scope and output. > > > > > > Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> > > > --- > > > tools/objtool/Makefile | 2 +- > > > tools/objtool/arch/loongarch/decode.c | 6 + > > > tools/objtool/arch/powerpc/decode.c | 6 + > > > tools/objtool/arch/x86/decode.c | 7 + > > > tools/objtool/check.c | 4 +- > > > tools/objtool/disas.c | 186 +++++++++++++++--------- > > > tools/objtool/include/objtool/arch.h | 5 + > > > tools/objtool/include/objtool/check.h | 5 + > > > tools/objtool/include/objtool/objtool.h | 4 + > > > 9 files changed, 154 insertions(+), 71 deletions(-) > > > > > > diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile > > > index 8c20361dd100..00350fc7c662 100644 > > > --- a/tools/objtool/Makefile > > > +++ b/tools/objtool/Makefile > > > @@ -34,7 +34,7 @@ INCLUDES := -I$(srctree)/tools/include \ > > > # is passed here to match a legacy behavior. > > > WARNINGS := $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -Wno-packed -Wno-nested-externs > > > OBJTOOL_CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBELF_FLAGS) > > > -OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS) > > > +OBJTOOL_LDFLAGS := $(LIBELF_LIBS) $(LIBSUBCMD) $(KBUILD_HOSTLDFLAGS) -lopcodes > > > > Would it be possible to make this optional? Such that when people do not > > have libopcodes installed they can still build the kernel. > > > > Or is libopcodes a mandatory part of any binutils installation? > > I guess that libopcodes is mandatory because it is used by as (and also objdump). > But I can check if it is effectively present anyway. libopcodes should always be present, but compiling/linking against it shouldn't be possible unless a binutils devel pkg is installed. So I think Peter's basically asking for what I asked for: make all this optional depending on whether the binutils devel pkg is installed, and print a helpful error message if somebody tries to use without. -- Josh
On Fri, Jun 06, 2025 at 05:34:30PM +0200, Alexandre Chartre wrote: > + dctx->disassembler = disassembler(dinfo->arch, > + dinfo->endian == BFD_ENDIAN_BIG, > + dinfo->mach, NULL); These lines should be aligned like: dctx->disassembler = disassembler(dinfo->arch, dinfo->endian == BFD_ENDIAN_BIG, dinfo->mach, NULL); -- Josh
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