V4 [PATCH 2/2] ld.so: Add --list-tunables to print tunable values
Adhemerval Zanella
adhemerval.zanella@linaro.org
Thu Jan 14 18:35:43 GMT 2021
On 31/10/2020 12:44, H.J. Lu via Libc-alpha wrote:
> Pass --list-tunables to ld.so to print tunables with min and max values.
> ---
> NEWS | 2 ++
> elf/Makefile | 8 ++++++++
> elf/dl-main.h | 2 +-
> elf/dl-tunables.c | 36 ++++++++++++++++++++++++++++++++++++
> elf/dl-tunables.h | 2 ++
> elf/dl-usage.c | 7 ++++++-
> elf/rtld.c | 23 +++++++++++++++++++++++
> manual/tunables.texi | 37 +++++++++++++++++++++++++++++++++++++
> 8 files changed, 115 insertions(+), 2 deletions(-)
>
> diff --git a/NEWS b/NEWS
> index 4307c4b1b0..a62e7307ef 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -9,6 +9,8 @@ Version 2.33
>
> Major new features:
>
> +* Pass --list-tunables to ld.so to print tunable values.
> +
Maybe use a similar sentence as for argv0:
* The dynamic linker accepts the --list-tunables argument which prints
all the supported tunables. This option is disable is glibc is
configured with tunables disabled (--enable-tunables=no).
> * The dynamic linker accepts the --argv0 argument and provides opportunity
> to change argv[0] string.
>
> diff --git a/elf/Makefile b/elf/Makefile
> index f10cc59e7c..86b282a32b 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -44,6 +44,10 @@ dl-routines += dl-tunables
> tunables-type = $(addprefix TUNABLES_FRONTEND_,$(have-tunables))
> CPPFLAGS-dl-tunables.c += -DTUNABLES_FRONTEND=$(tunables-type)
>
> +ifeq (yesyes,$(build-shared)$(run-built-tests))
> +tests-special += $(objpfx)list-tunables.out
> +endif
> +
> # Make sure that the compiler does not insert any library calls in tunables
> # code paths.
Ok, it is enabled iff 'ifneq (no,$(have-tunables))'.
> ifeq (yes,$(have-loop-to-function))
> @@ -1812,3 +1816,7 @@ $(objpfx)argv0test.out: tst-rtld-argv0.sh $(objpfx)ld.so \
> '$(test-wrapper-env)' '$(run_program_env)' \
> '$(rpath-link)' 'test-argv0' > $@; \
> $(evaluate-test)
> +
> +$(objpfx)list-tunables.out: $(objpfx)ld.so
> + $(objpfx)ld.so --list-tunables > $@; \
> + $(evaluate-test)
Maybe at least check for a tunable with a default value which be
equal to all architecture, like glibc.rtld.nns, glibc.malloc.perturb, etc?
> diff --git a/elf/dl-main.h b/elf/dl-main.h
> index b51256d3b4..f229867b8e 100644
> --- a/elf/dl-main.h
> +++ b/elf/dl-main.h
> @@ -63,7 +63,7 @@ struct audit_list
> enum rtld_mode
> {
> rtld_mode_normal, rtld_mode_list, rtld_mode_verify, rtld_mode_trace,
> - rtld_mode_help,
> + rtld_mode_list_tunables, rtld_mode_help,
> };
>
> /* Aggregated state information extracted from environment variables
Ok.
> diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> index 2ba2844075..048601b704 100644
> --- a/elf/dl-tunables.c
> +++ b/elf/dl-tunables.c
> @@ -398,6 +398,42 @@ __tunables_init (char **envp)
> }
> }
>
> +void
> +__tunables_print (void)
> +{
> + for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
Use array_length here.
> + {
> + tunable_t *cur = &tunable_list[i];
Maybe use a const modifier here.
> + _dl_printf ("%s: ", cur->name);
> + switch (cur->type.type_code)
> + {
> + case TUNABLE_TYPE_INT_32:
> + _dl_printf ("%d (min: %d, max: %d)\n",
> + (int) cur->val.numval,
> + (int) cur->type.min,
> + (int) cur->type.max);
> + break;
> + case TUNABLE_TYPE_UINT_64:
> + _dl_printf ("0x%lx (min: 0x%lx, max: 0x%lx)\n",
> + (long int) cur->val.numval,
> + (long int) cur->type.min,
> + (long int) cur->type.max);
> + break;
> + case TUNABLE_TYPE_SIZE_T:
> + _dl_printf ("0x%Zx (min: 0x%Zx, max: 0x%Zx)\n",
> + (size_t) cur->val.numval,
> + (size_t) cur->type.min,
> + (size_t) cur->type.max);
> + break;
> + case TUNABLE_TYPE_STRING:
> + _dl_printf ("%s\n", cur->val.strval ? cur->val.strval : "");
> + break;
> + default:
> + __builtin_unreachable ();
> + }
> + }
> +}
> +
Ok, it should be ok to use '%d' for signed and 'lx' for unsigned.
> /* Set the tunable value. This is called by the module that the tunable exists
> in. */
> void
> diff --git a/elf/dl-tunables.h b/elf/dl-tunables.h
> index 550b0cc7f4..4a0c90f3e0 100644
> --- a/elf/dl-tunables.h
> +++ b/elf/dl-tunables.h
> @@ -69,9 +69,11 @@ typedef struct _tunable tunable_t;
> # include "dl-tunable-list.h"
>
> extern void __tunables_init (char **);
> +extern void __tunables_print (void);
> extern void __tunable_get_val (tunable_id_t, void *, tunable_callback_t);
> extern void __tunable_set_val (tunable_id_t, void *, void *, void *);
> rtld_hidden_proto (__tunables_init)
> +rtld_hidden_proto (__tunables_print)
> rtld_hidden_proto (__tunable_get_val)
> rtld_hidden_proto (__tunable_set_val)
>
Ok.
> diff --git a/elf/dl-usage.c b/elf/dl-usage.c
> index 796ad38b43..3ce19fb892 100644
> --- a/elf/dl-usage.c
> +++ b/elf/dl-usage.c
> @@ -190,7 +190,12 @@ setting environment variables (which would be inherited by subprocesses).\n\
> in LIST\n\
> --audit LIST use objects named in LIST as auditors\n\
> --preload LIST preload objects named in LIST\n\
> - --argv0 STRING set argv[0] to STRING before running\n\
> + --argv0 STRING set argv[0] to STRING before running\n"
> +#if HAVE_TUNABLES
> +"\
> + --list-tunables list all tunables with minimum and maximum values\n"
> +#endif
> +"\
> --help display this help and exit\n\
> --version output version information and exit\n\
> \n\
Ok.
> diff --git a/elf/rtld.c b/elf/rtld.c
> index 5d117d0d2c..33993a6f8b 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -49,6 +49,10 @@
> #include <libc-early-init.h>
> #include <dl-main.h>
>
> +#if HAVE_TUNABLES
> +# include <dl-tunables.h>
> +#endif
> +
You can include this header regadless of HAVE_TUNABLES (it handles it
internally).
> #include <assert.h>
>
> /* Only enables rtld profiling for architectures which provides non generic
> @@ -1248,6 +1252,16 @@ dl_main (const ElfW(Phdr) *phdr,
> _dl_argc -= 2;
> _dl_argv += 2;
> }
> +#if HAVE_TUNABLES
> + else if (! strcmp (_dl_argv[1], "--list-tunables"))
> + {
> + state.mode = rtld_mode_list_tunables;
> +
> + ++_dl_skip_args;
> + --_dl_argc;
> + ++_dl_argv;
> + }
> +#endif
> else if (strcmp (_dl_argv[1], "--help") == 0)
> {
> state.mode = rtld_mode_help;
> @@ -1268,6 +1282,15 @@ dl_main (const ElfW(Phdr) *phdr,
> else
> break;
>
> +#if HAVE_TUNABLES
> + if (__builtin_expect (state.mode, rtld_mode_normal)
> + == rtld_mode_list_tunables)
Use
if (__glibc_unlikely (state.mode == rtld_mode_list_tunables)
> + {
> + __tunables_print ();
> + _exit (0);
> + }
> +#endif
> +
> /* If we have no further argument the program was called incorrectly.
> Grant the user some education. */
> if (_dl_argc < 2)
> diff --git a/manual/tunables.texi b/manual/tunables.texi
> index d72d7a5ec0..924dac8876 100644
> --- a/manual/tunables.texi
> +++ b/manual/tunables.texi
> @@ -28,6 +28,43 @@ Finally, the set of tunables available may vary between distributions as
> the tunables feature allows distributions to add their own tunables under
> their own namespace.
>
> +Passing @option{--list-tunables} to the dynamic loader to print all
> +tunables with minimum and maximum values:
> +
> +@example
> +$ /lib64/ld-linux-x86-64.so.2 --list-tunables
> +glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
> +glibc.elision.skip_lock_after_retries: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.perturb: 0 (min: 0, max: 255)
> +glibc.cpu.x86_shared_cache_size: 0x100000 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.elision.tries: 3 (min: -2147483648, max: 2147483647)
> +glibc.elision.enable: 0 (min: 0, max: 1)
> +glibc.cpu.x86_rep_movsb_threshold: 0x800 (min: 0x100, max: 0xffffffffffffffff)
> +glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.elision.skip_lock_busy: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_rep_stosb_threshold: 0x800 (min: 0x1, max: 0xffffffffffffffff)
> +glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_shstk:
Trailing whitespace.
> +glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
> +glibc.elision.skip_trylock_internal_abort: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_ibt:
Ditto.
> +glibc.cpu.hwcaps:
Ditto.
> +glibc.elision.skip_lock_internal_abort: 3 (min: -2147483648, max: 2147483647)
> +glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0xffffffffffffffff)
> +glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.cpu.x86_data_cache_size: 0x8000 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.tcache_count: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.arena_test: 0x0 (min: 0x1, max: 0xffffffffffffffff)
> +glibc.pthread.mutex_spin_count: 100 (min: 0, max: 32767)
> +glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.tcache_max: 0x0 (min: 0x0, max: 0xffffffffffffffff)
> +glibc.malloc.check: 0 (min: 0, max: 3)
> +@end example
> +
> @menu
> * Tunable names:: The structure of a tunable name
> * Memory Allocation Tunables:: Tunables in the memory allocation subsystem
>
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