Date:	Thu, 21 Mar 2013 12:15:12 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Fengguang Wu <fengguang.wu@...el.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Bob Liu <lliubbo@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-kbuild <linux-kbuild@...r.kernel.org>,
	David Howells <dhowells@...hat.com>
Subject: Re: make[2]: execvp: /bin/bash: Argument list too long

Andrew Morton <akpm@...ux-foundation.org> writes:
> On Wed, 20 Mar 2013 13:41:07 +1030 Rusty Russell <rusty@...tcorp.com.au> wrote:
>
>> Fengguang Wu <fengguang.wu@...el.com> writes:
>> > On Tue, Mar 19, 2013 at 09:10:25AM -0400, Konrad Rzeszutek Wilk wrote:
>> >> On Mon, Mar 18, 2013 at 11:50:58PM -0700, Andrew Morton wrote:
>> >> > On Tue, 19 Mar 2013 14:31:40 +0800 kbuild test robot <fengguang.wu@...el.com> wrote:
>> >> > 
>> >> > > tree:   git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next master
>> >> > > head:   0e78c0989334e9c1d578ba25621de14e8441d8b4
>> >> > > commit: 7cac5501aa2bd4777906fa0cdccc1b1ce18b3166 staging: zcache: enable zcache to be built/loaded as a module
>> >> > > date:   26 hours ago
>> >> > > config: make ARCH=i386 allmodconfig
>> >> > > 
>> >> > > All error/warnings:
>> >> > > 
>> >> > > >> make[2]: execvp: /bin/bash: Argument list too long
>> >> > >    make[2]: *** [__modpost] Error 127
>> >> > >    make[2]: Target `_modpost' not remade because of errors.
>> >> > > 
>> >> > 
>> >> > Hey, I see that very occasionally, but it goes away all by itself.  Are
>> >> > you sure that
>> >> > staging-zcache-enable-ramster-to-be-built-loaded-as-a-module.patch
>> >> > causes it?
>> >
>> > Sorry, I confirmed that it's a wrong bisect..
>> >
>> >> Is there a way to print out what the argument list is?
>> >
>> > Good idea! I managed to catch the error command with
>> >
>> >         strace -e trace=process -s 4096 -f -o argtoolong make -j1 --debug=j V=1 ARCH=i386 modules
>> 
>> Wow, nice!
>
> That's what I thought.  A better approach would be to delete a few
> thousand drivers ;)
>
> I worry that we'll also explode some internal limit in make(1) when
> preparing that list.  We'll see.

make is used in some pretty unweildy projects, so I'd be surprised if we
hit that.

>> modpost really does want all the modules at once, so it can check for
>> unresolved symbols.  So xargs is out, we need to implement stdin-reading
>> directly.
>> 
>> Bikeshedding on the option name reveals no established standard:
>> -S/--stdin-file-list in shar, -T/--files-from=i in tar, --files-from=-
>> in rsync.
>
> Could just read the filenames from stdin if none were provided on the
> command line, but whatever.

That wouldn't be very unixy...

>> Now, if someone can find a better way of getting the module list into a
>> file/stdin, I'm all ears.  I'm not sure the find works in all cases...
>
> How is that list generated at present?
>
> So we have a vast string within make(1) and need to get it into a temp
> file without using shell commands?  Tricky.

Actually, this patch is *crap*.  modpost is what generates the .ko
files: we need the .o file equivalents.  The find command wouldn't work
on a clean tree...

But that's OK, we actually generate the module list above, so we can
reuse that same logic.

>> +	while (fgets(fname, PATH_MAX, in) != NULL) {
>> +		/* Strip \n */
>> +		if (strlen(fname))
>> +			fname[strlen(fname)-1] = '\0';
>
> That'll screw up if the file doesn't end in \n?

In a break-compile way, yes.  But fixed...

If this passes review, I'll split properly into three patches.

Thanks,
Rusty.

modpost: handle huge numbers of modules.

(FIXME: Split into multiple patches).

strace shows:
72102 execve("/bin/sh", ["/bin/sh", "-c", "echo '  scripts/mod/modpost -m -a
-o /cc/wfg/sound-compiletest/Module.symvers      -s'; scripts/
mod/modpost -m -a -o /cc/wfg/sound-compiletest/Module.symvers      -s vmlinux
arch/x86/crypto/ablk_helper.o arch/x86/crypto/aes-i586.o arch
/x86/crypto/aesni-intel.o arch/x86/crypto/crc32-pclmul.o
...
drivers/ata/sata_promise.o "...], [/* 119 vars */] <unfinished ...>
71827 wait4(-1,  <unfinished ...>
72102 <... execve resumed> )            = -1 E2BIG (Argument list too long)

Reported-by: Fengguang Wu <fengguang.wu@...el.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index cf82c83..8dcdca2 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -60,7 +60,8 @@ kernelsymfile := $(objtree)/Module.symvers
 modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
 
 # Step 1), find all modules listed in $(MODVERDIR)/
-__modules := $(sort $(shell grep -h '\.ko$$' /dev/null $(wildcard $(MODVERDIR)/*.mod)))
+MODLISTCMD := find $(MODVERDIR) -name '*.mod' | xargs -r grep -h '\.ko$$' | sort -u
+__modules := $(shell $(MODLISTCMD))
 modules   := $(patsubst %.o,%.ko, $(wildcard $(__modules:.ko=.o)))
 
 # Stop after building .o files if NOFINAL is set. Makes compile tests quicker
@@ -78,12 +79,13 @@ modpost = scripts/mod/modpost                    \
  $(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S)      \
  $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w)
 
+# We can go over command line length here, so be careful.
 quiet_cmd_modpost = MODPOST $(words $(filter-out vmlinux FORCE, $^)) modules
-      cmd_modpost = $(modpost) -s
+      cmd_modpost = $(MODLISTCMD) | sed 's/\.ko$$/.o/' | $(modpost) -s -T -
 
 PHONY += __modpost
 __modpost: $(modules:.ko=.o) FORCE
-	$(call cmd,modpost) $(wildcard vmlinux) $(filter-out FORCE,$^)
+	$(call cmd,modpost) $(wildcard vmlinux)
 
 quiet_cmd_kernel-mod = MODPOST $@
       cmd_kernel-mod = $(modpost) $@
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f6913db..1f90961 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -15,6 +15,8 @@
 #include <stdio.h>
 #include <ctype.h>
 #include <string.h>
+#include <limits.h>
+#include <stdbool.h>
 #include "modpost.h"
 #include "../../include/generated/autoconf.h"
 #include "../../include/linux/license.h"
@@ -78,6 +80,14 @@ PRINTF void merror(const char *fmt, ...)
 	va_end(arglist);
 }
 
+static inline bool strends(const char *str, const char *postfix)
+{
+	if (strlen(str) < strlen(postfix))
+		return false;
+
+	return strcmp(str + strlen(str) - strlen(postfix), postfix) == 0;
+}
+
 static int is_vmlinux(const char *modname)
 {
 	const char *myname;
@@ -113,22 +123,20 @@ static struct module *find_module(char *modname)
 	return mod;
 }
 
-static struct module *new_module(char *modname)
+static struct module *new_module(const char *modname)
 {
 	struct module *mod;
-	char *p, *s;
+	char *p;
 
 	mod = NOFAIL(malloc(sizeof(*mod)));
 	memset(mod, 0, sizeof(*mod));
 	p = NOFAIL(strdup(modname));
 
 	/* strip trailing .o */
-	s = strrchr(p, '.');
-	if (s != NULL)
-		if (strcmp(s, ".o") == 0) {
-			*s = '\0';
-			mod->is_dot_o = 1;
-		}
+	if (strends(p, ".o")) {
+		p[strlen(p) - 2] = '\0';
+		mod->is_dot_o = 1;
+	}
 
 	/* add to list */
 	mod->name = p;
@@ -1756,6 +1764,27 @@ static void read_symbols(char *modname)
 		mod->unres = alloc_symbol("module_layout", 0, mod->unres);
 }
 
+static void read_symbols_from_files(const char *filename)
+{
+	FILE *in = stdin;
+	char fname[PATH_MAX];
+
+	if (strcmp(filename, "-") != 0) {
+		in = fopen(filename, "r");
+		if (!in)
+			fatal("Can't open filenames file %s: %m", filename);
+	}
+
+	while (fgets(fname, PATH_MAX, in) != NULL) {
+		if (strends(fname, "\n"))
+			fname[strlen(fname)-1] = '\0';
+		read_symbols(fname);
+	}
+
+	if (in != stdin)
+		fclose(in);
+}
+
 #define SZ 500
 
 /* We first write the generated file into memory using the
@@ -2117,13 +2146,13 @@ int main(int argc, char **argv)
 	struct module *mod;
 	struct buffer buf = { };
 	char *kernel_read = NULL, *module_read = NULL;
-	char *dump_write = NULL;
+	char *dump_write = NULL, *files_source = NULL;
 	int opt;
 	int err;
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
-	while ((opt = getopt(argc, argv, "i:I:e:msSo:awM:K:")) != -1) {
+	while ((opt = getopt(argc, argv, "i:I:e:msST:o:awM:K:")) != -1) {
 		switch (opt) {
 		case 'i':
 			kernel_read = optarg;
@@ -2155,6 +2184,9 @@ int main(int argc, char **argv)
 		case 'S':
 			sec_mismatch_verbose = 0;
 			break;
+		case 'T':
+			files_source = optarg;
+			break;
 		case 'w':
 			warn_unresolved = 1;
 			break;
@@ -2177,6 +2209,9 @@ int main(int argc, char **argv)
 	while (optind < argc)
 		read_symbols(argv[optind++]);
 
+	if (files_source)
+		read_symbols_from_files(files_source);
+
 	for (mod = modules; mod; mod = mod->next) {
 		if (mod->skip)
 			continue;
--
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