Commit 33221307 authored by Quentin Monnet's avatar Quentin Monnet Committed by Daniel Borkmann
Browse files

tools: bpftool: add an option to prevent auto-mount of bpffs, tracefs 



In order to make life easier for users, bpftool automatically attempts
to mount the BPF virtual file system, if it is not mounted already,
before trying to pin objects in it. Similarly, it attempts to mount
tracefs if necessary before trying to dump the trace pipe to the
console.

While mounting file systems on-the-fly can improve user experience, some
administrators might prefer to avoid that. Let's add an option to block
these mount attempts. Note that it does not prevent automatic mounting
of tracefs by debugfs for the "bpftool prog tracelog" command.

Signed-off-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent be3245e2

tools/bpf/bpftool/Documentation/bpftool-map.rst

+4 −0
Original line number Original line Diff line number Diff line
@@ -128,6 +128,10 @@ OPTIONS 
	-f, --bpffs

	-f, --bpffs

		  Show file names of pinned maps.

		  Show file names of pinned maps.





	-n, --nomount

		  Do not automatically attempt to mount any virtual file system

		  (such as tracefs or BPF virtual file system) when necessary.



EXAMPLES

EXAMPLES

========

========

**# bpftool map show**

**# bpftool map show**

tools/bpf/bpftool/Documentation/bpftool-prog.rst

+4 −0
Original line number Original line Diff line number Diff line
@@ -161,6 +161,10 @@ OPTIONS 
	-m, --mapcompat

	-m, --mapcompat

		  Allow loading maps with unknown map definitions.

		  Allow loading maps with unknown map definitions.





	-n, --nomount

		  Do not automatically attempt to mount any virtual file system

		  (such as tracefs or BPF virtual file system) when necessary.



EXAMPLES

EXAMPLES

========

========

**# bpftool prog show**

**# bpftool prog show**

tools/bpf/bpftool/Documentation/bpftool.rst

+4 −0
Original line number Original line Diff line number Diff line
@@ -60,6 +60,10 @@ OPTIONS 
	-m, --mapcompat

	-m, --mapcompat

		  Allow loading maps with unknown map definitions.

		  Allow loading maps with unknown map definitions.





	-n, --nomount

		  Do not automatically attempt to mount any virtual file system

		  (such as tracefs or BPF virtual file system) when necessary.







SEE ALSO

SEE ALSO

========

========

tools/bpf/bpftool/common.c

+6 −0
Original line number Original line Diff line number Diff line
@@ -177,6 +177,12 @@ int mount_bpffs_for_pin(const char *name) 
		/* nothing to do if already mounted */

		/* nothing to do if already mounted */

		goto out_free;

		goto out_free;





	if (block_mount) {

		p_err("no BPF file system found, not mounting it due to --nomount option");

		err = -1;

		goto out_free;

	}



	err = mnt_fs(dir, "bpf", err_str, ERR_MAX_LEN);

	err = mnt_fs(dir, "bpf", err_str, ERR_MAX_LEN);

	if (err) {

	if (err) {

		err_str[ERR_MAX_LEN - 1] = '\0';

		err_str[ERR_MAX_LEN - 1] = '\0';

tools/bpf/bpftool/main.c

+7 −1
Original line number Original line Diff line number Diff line
@@ -24,6 +24,7 @@ json_writer_t *json_wtr; 
bool pretty_output;

bool pretty_output;

bool json_output;

bool json_output;

bool show_pinned;

bool show_pinned;

bool block_mount;

int bpf_flags;

int bpf_flags;

struct pinned_obj_table prog_table;

struct pinned_obj_table prog_table;

struct pinned_obj_table map_table;

struct pinned_obj_table map_table;
@@ -313,6 +314,7 @@ int main(int argc, char **argv) 
		{ "version",	no_argument,	NULL,	'V' },

		{ "version",	no_argument,	NULL,	'V' },

		{ "bpffs",	no_argument,	NULL,	'f' },

		{ "bpffs",	no_argument,	NULL,	'f' },

		{ "mapcompat",	no_argument,	NULL,	'm' },

		{ "mapcompat",	no_argument,	NULL,	'm' },

		{ "nomount",	no_argument,	NULL,	'n' },

		{ 0 }

		{ 0 }

	};

	};

	int opt, ret;

	int opt, ret;
@@ -321,13 +323,14 @@ int main(int argc, char **argv) 
	pretty_output = false;

	pretty_output = false;

	json_output = false;

	json_output = false;

	show_pinned = false;

	show_pinned = false;

	block_mount = false;

	bin_name = argv[0];

	bin_name = argv[0];





	hash_init(prog_table.table);

	hash_init(prog_table.table);

	hash_init(map_table.table);

	hash_init(map_table.table);





	opterr = 0;

	opterr = 0;

	while ((opt = getopt_long(argc, argv, "Vhpjfm",

	while ((opt = getopt_long(argc, argv, "Vhpjfmn",

				  options, NULL)) >= 0) {

				  options, NULL)) >= 0) {

		switch (opt) {

		switch (opt) {

		case 'V':

		case 'V':
@@ -354,6 +357,9 @@ int main(int argc, char **argv) 
		case 'm':

		case 'm':

			bpf_flags = MAPS_RELAX_COMPAT;

			bpf_flags = MAPS_RELAX_COMPAT;

			break;

			break;

		case 'n':

			block_mount = true;

			break;

		default:

		default:

			p_err("unrecognized option '%s'", argv[optind - 1]);

			p_err("unrecognized option '%s'", argv[optind - 1]);

			if (json_output)

			if (json_output)

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