[PATCH] powerpc: Allow selection of CONFIG_LD_DEAD_CODE_DATA_ELIMINATION

[Christophe LEROY]

Le 17/04/2018 à 19:10, Mathieu Malaterre a écrit :
> On Tue, Apr 17, 2018 at 6:49 PM, Christophe LEROY
> <christophe.leroy at c-s.fr> wrote:
>>
>>
>> Le 17/04/2018 à 18:45, Mathieu Malaterre a écrit :
>>>
>>> On Tue, Apr 17, 2018 at 12:49 PM, Christophe Leroy
>>> <christophe.leroy at c-s.fr> wrote:
>>>>
>>>> This option does dead code and data elimination with the linker by
>>>> compiling with -ffunction-sections -fdata-sections and linking with
>>>> --gc-sections.
>>>>
>>>> By selecting this option on mpc885_ads_defconfig,
>>>> vmlinux LOAD segment size gets reduced by 10%
>>>>
>>>> Program Header before the patch:
>>>>       LOAD off    0x00010000 vaddr 0xc0000000 paddr 0x00000000 align 2**16
>>>>            filesz 0x0036eda4 memsz 0x0038de04 flags rwx
>>>>
>>>> Program Header after the patch:
>>>>       LOAD off    0x00010000 vaddr 0xc0000000 paddr 0x00000000 align 2**16
>>>>            filesz 0x00316da4 memsz 0x00334268 flags rwx
>>>>
>>>> Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
>>>> ---
>>>>    arch/powerpc/Kconfig | 8 ++++++++
>>>>    1 file changed, 8 insertions(+)
>>>>
>>>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>>>> index 8fe4353be5e3..e1fac49cf465 100644
>>>> --- a/arch/powerpc/Kconfig
>>>> +++ b/arch/powerpc/Kconfig
>>>> @@ -888,6 +888,14 @@ config PPC_MEM_KEYS
>>>>
>>>>             If unsure, say y.
>>>>
>>>> +config PPC_UNUSED_ELIMINATION
>>>> +       bool "Eliminate unused functions and data from vmlinux"
>>>> +       default n
>>>> +       select LD_DEAD_CODE_DATA_ELIMINATION
>>>> +       help
>>>> +         Select this to do dead code and data elimination with the
>>>> linker
>>>> +         by compiling with -ffunction-sections -fdata-sections and
>>>> linking
>>>> +         with --gc-sections.
>>>>    endmenu
>>>>
>>>
>>> Just for reference, I cannot boot my Mac Mini G4 anymore (yaboot). The
>>> messages I can see (prom_init) are:
>>
>>
>> Which version of GCC do you use ?
> 
> $ powerpc-linux-gnu-gcc --version
> powerpc-linux-gnu-gcc (Debian 6.3.0-18) 6.3.0 20170516
> Copyright (C) 2016 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> 
> this is simply coming from:
> 
> $ apt-cache policy crossbuild-essential-powerpc
> crossbuild-essential-powerpc:
>    Installed: 12.3
>    Candidate: 12.3
>    Version table:
>   *** 12.3 500
>          500 http://ftp.fr.debian.org/debian stretch/main amd64 Packages
>          500 http://ftp.fr.debian.org/debian stretch/main i386 Packages
>          100 /var/lib/dpkg/status
> 
> 
>> Can you provide the generated System.map with and without that option active
>> ?
> 
> $ du -sh g4/System.map.*
> 1.7M g4/System.map.with
> 1.8M g4/System.map.without

Here below is the list of objects removed with the option selected. I 
can't see anything suspect at first.
Do you use one of the defconfigs of the kernel ? Otherwise, can you 
provide your .config ?
Can you also provide a copy of the messages you can see (prom_init ...) 
when boot is ok ?
Maybe you can also send me the two vmlinux objects.

Thanks
Christophe

account_steal_time
adbhid_exit
adb_reset_bus
add_range
add_range_with_merge
aes_fini
af_unix_exit
agp_exit
agp_find_client_by_pid
agp_find_mem_by_key
agp_find_private
agp_free_memory_wrap
agpioc_protect_wrap
agpioc_release_wrap
agp_uninorth_cleanup
__alloc_reserved_percpu
all_stat_sessions
all_stat_sessions_mutex
apple_driver_exit
arch_cpu_idle_dead
arch_setup_msi_irq
arch_teardown_msi_irq
arch_tlb_gather_mmu
asymmetric_key_cleanup
asymmetric_key_hex_to_key_id
ata_exit
ata_tf_to_lba
ata_tf_to_lba48
attribute_container_add_class_device_adapter
attribute_container_trigger
backlight_class_exit
bdi_lock
bhrb_table
biovec_create_pool
blk_stat_enable_accounting
boot_mapsize
bpf_map_meta_equal
bvec_free
bvec_nr_vecs
calc_load_fold_active
can_request_irq
capacity_margin
cap_inode_getsecurity
cap_mmap_file
cfq_exit
cgroup_is_threaded
cgroup_is_thread_root
cgroup_migrate_add_src
cgroup_migrate_vet_dst
cgroup_on_dfl
cgroup_sk_update_lock
cgroupstats_build
cgroup_task_count
cgroup_transfer_tasks
change_protection
clean_sort_range
clear_ftrace_function
clear_zone_contiguous
__clockevents_update_freq
clockevents_update_freq
clocksource_mark_unstable
clocksource_touch_watchdog
clone_property.isra.2
cmp_range
cn_fini
cn_queue_free_dev
collect_mounts
compaction_restarting
copy_fpr_from_user
copy_fpr_to_user
copy_mount_string
copy_msg
cpu_check_up_prepare
cpufreq_boost_trigger_state
cpufreq_gov_performance_exit
cpu_hotplug_state
cpu_in_idle
cpu_report_state
cpu_set_state_online
cpu_temp
crashk_low_res
crash_wake_offline
create_prof_cpu_mask
crypto_algapi_exit
crypto_exit_proc
crypto_null_mod_fini
crypto_wq_exit
css_rightmost_descendant
css_set_lock
cubictcp_unregister
__current_kernel_time
d_absolute_path
dbg_release_bp_slot
dbg_reserve_bp_slot
deadline_exit
deadline_exit
debug_guardpage_ops
default_restore_msi_irqs
default_teardown_msi_irqs
del_named_trigger
dereference_module_function_descriptor
__dev_pm_qos_flags
dev_pm_qos_read_value
devtree_lock
die_will_crash
disable_cpufreq
dma_buf_deinit
dma_common_contiguous_remap
dma_common_pages_remap
__dma_get_required_mask
dma_pfn_limit_to_zone
do_execveat
do_fork
__domain_nr
do_msg_redirect_map
do_pipe_flags
do_sk_redirect_map
drmem_lmb_memory_max
drmem_update_dt
dst_discard
dummy_cmp
dump_cpu_task
dump_stack_set_arch_desc
earlycon_acpi_spcr_enable
early_find_capability
early_printk
early_read_config_byte
early_write_config_byte
exar_pci_driver_exit
exit_elf_binfmt
exit_misc_binfmt
exit_pmz
exit_script_binfmt
exit_scsi
fdt_add_mem_rsv
fdt_add_property_
fdt_add_subnode
fdt_add_subnode_namelen
fdt_appendprop
fdt_del_mem_rsv
fdt_del_node
fdt_delprop
fdt_find_string_
fdt_get_alias
fdt_get_max_phandle
fdt_get_path
fdt_get_property
fdt_get_property_by_offset
fdt_get_property_namelen
fdt_move
fdt_node_depth
fdt_node_end_offset_
fdt_node_offset_by_compatible
fdt_node_offset_by_phandle
fdt_node_offset_by_prop_value
fdt_nop_node
fdt_nop_property
fdt_num_mem_rsv
fdt_offset_ptr
fdt_open_into
fdt_pack
fdt_packblocks_
fdt_rw_check_header_
fdt_set_name
fdt_setprop
fdt_setprop_inplace
fdt_setprop_inplace_namelen_partial
fdt_setprop_placeholder
fdt_splice_
fdt_string
fdt_stringlist_count
fdt_stringlist_get
fdt_stringlist_search
fdt_subnode_offset
feature_lock
fib_table_flush_external
fib_trie_unmerge
fib_unmerge
find_named_trigger
__finish_swait
firmware_class_exit
fixup_red_left
force_printk_to_btext
force_sig_bnderr
force_sig_fault
force_sig_pkuerr
force_sig_ptrace_errno_trap
fork_idle
fprop_fraction_single
__fprop_inc_percpu
__fprop_inc_single
fprop_local_destroy_single
fprop_local_init_single
free_page_and_swap_cache
free_workqueue_attrs
fsl_mpic_primary_get_version
fsnotify_add_mark
fsnotify_finish_user_wait
fsnotify_get_mark_safe
fsnotify_prepare_user_wait
fsnotify_put_mark_wake
ftrace_exports
ftrace_get_addr_curr
ftrace_get_addr_new
ftrace_graph_ret_addr
ftrace_graph_stop
ftrace_nr_registered_ops
ftrace_ops_assist_func
ftrace_ops_get_func
ftrace_ops_trampoline
ftrace_run_stop_machine
ftrace_test_record
ftrace_text_reserved
__func__.3126
__func__.53147
func_ptr_is_kernel_text
generic_ptrace_pokedata
generic_rtc_driver_exit
__get_cached_msi_msg
get_cpu_cacheinfo
get_iowait_load
get_named_trigger_data
get_safe_page
get_syscall_name
get_vm_area
__get_vm_area_caller
grub_reclaim
gup_fast_permitted
gup_hugepte
handle_hmi_exception
handle_percpu_devid_irq
handle_percpu_irq
has_unmovable_pages
has_unmovable_pages.part.31
hdec_interrupt
hid_debug_exit
hid_exit
hid_generic_exit
hidraw_exit
hrtimers_prepare_cpu
hwmon_exit
i2c_register_board_info
igmp_mcf_get_next.isra.4
igmp_mcf_seq_fops
igmp_mcf_seq_next
igmp_mcf_seq_open
igmp_mcf_seq_ops
igmp_mcf_seq_show
igmp_mcf_seq_start
igmp_mcf_seq_stop
igmp_mc_init
igmp_mc_seq_fops
igmp_mc_seq_next
igmp_mc_seq_open
igmp_mc_seq_ops
igmp_mc_seq_show
igmp_mc_seq_start
igmp_mc_seq_stop
igmp_netdev_event
igmp_net_exit
igmp_net_init
igmp_net_ops
igmp_notifier
init_cpu_online
init_cpu_possible
init_cpu_present
init_kernel_text
init_thread_info
input_exit
input_leds_exit
insert_resource_conflict
insert_resource_expand_to_fit
insert_stat
instr_is_branch_to_addr
instr_is_relative_link_branch
iomem_map_sanity_check
io_range_mutex
ip6_ra_lock
ipv4_blackhole_route
ipv6_renew_options_kern
ipv6_sysctl_unregister
irq_chip_compose_msi_msg
irqchip_init
irq_cpu_offline
irq_cpu_online
irq_domain_set_info
irq_domain_update_bus_token
irq_get_next_irq
irq_set_percpu_devid
irq_set_percpu_devid_partition
isa_io_special
is_file_shm_hugepages
is_hardlockup
__is_kernel_percpu_address
is_kernel_percpu_address
is_module_address
__is_module_percpu_address
is_module_percpu_address
is_named_trigger
is_offset_in_branch_range
isolate_freepages_range
isolate_migratepages_range
is_pageblock_removable_nolock
__is_ram
is_tracing_stopped
is_vmalloc_or_module_addr
is_vma_temporary_stack
iterate_mounts
k2_skiplist
kcompactd_stop
__key.36706
keyctl_negate_key
key_serial_lock
kimage_is_destination_range
kmap_flush_unused
__kmem_cache_alloc_bulk
__kmem_cache_empty
kobj_child_ns_ops
kobj_ns_initial
kobj_ns_netlink
kobj_ns_type_registered
kretprobe_blacklist
kstat_incr_irq_this_cpu
kswapd_stop
ldsem_down_write_trylock
leds_exit
libata_transport_exit
lockup_detector_cleanup
lockup_detector_soft_poweroff
log_buf_addr_get
log_buf_len_get
logbuf_lock
logic_pio_register_range
logic_pio_to_hwaddr
logic_pio_trans_cpuaddr
lookup_module_symbol_attrs
lookup_page_ext
lookup_resource
lookup_symbol_attrs
mac_var_to_vmode
map_kernel_range_noflush
max_cfs_quota_period
max_possible_pfn
memblock_add_node
memblock_clear_nomap
memblock_get_current_limit
memblock_is_map_memory
memblock_is_region_memory
memblock_is_region_reserved
memblock_mark_mirror
memblock_mark_nomap
memblock_overlaps_region
memblock_reserved_size
memblock_start_of_DRAM
memblock_trim_memory
metadata_dst_free
migrate_huge_page_move_mapping
migrate_prep
migrate_reason_names
migration_entry_wait_huge
min_cfs_quota_period
mmc_blk_exit
mmc_exit
mmc_pwrseq_emmc_driver_exit
mmc_pwrseq_simple_driver_exit
mm_find_pmd
mmlist_lock
mmput_async
mmput_async_fn
mnt_clone_internal
mousedev_exit
mpc6xx_enter_standby
mpic_get_one_irq
mpic_setup_this_cpu
named_triggers
n_null_exit
noop_exit
nr_free_pagecache_pages
nsecs_to_usecs
num_powerpc_operands
nvmem_exit
nvram_cleanup
of_device_compatible_match
of_fdt_is_big_endian
of_fdt_limit_memory
__of_find_all_nodes
of_find_last_cache_level
of_find_matching_node_by_address
of_get_flat_dt_subnode_by_name
__of_get_property
of_msi_map_get_device_domain
__of_msi_map_rid
of_msi_map_rid
of_node_is_attached
of_parse_dma_window
of_pci_map_rid
of_print_phandle_args
__of_remove_property
__of_sysfs_remove_bin_file
oops_may_print
our_mnt
p4d_clear_bad
packet_exit
page_counter_cancel
page_mapped_in_vma
page_mapping_file
page_unlock_anon_vma_read
panic_flush_kmsg_end
panic_flush_kmsg_start
pata_macio_exit
patch_branch
pause_named_trigger
__pause_named_trigger.isra.4
pci_acs_enabled
pci_acs_flags_enabled
pci_acs_path_enabled
pci_add_cap_save_buffer
pcibios_max_latency
pcibios_penalize_isa_irq
pcibios_resource_survey_bus
pci_bridge_group
pci_bridge_groups
pci_bus_set_current_state
pci_dev_acs_enabled
pci_devs_are_dma_aliases
pci_dev_specific_acs_enabled
pcie_cap_has_lnkctl
pcie_dev_group
pcie_dev_groups
pci_ext_cfg_avail
pci_for_each_dma_alias
pci_get_interrupt_pin
pci_get_new_domain_nr
pci_lock
__pci_msix_desc_mask_irq
pci_parse_request_of_pci_ranges
pci_pio_to_address
pci_pme_wakeup
pci_pme_wakeup_bus
pci_quirk_amd_sb_acs
pci_quirk_cavium_acs
pci_quirk_intel_pch_acs
pci_quirk_intel_spt_pch_acs
pci_quirk_mf_endpoint_acs
pci_quirk_qcom_rp_acs
pci_quirk_xgene_acs
pci_request_acs
pci_set_platform_pm
pci_setup_bridge
pci_wakeup_bus
pcpu_lock
perf_duration_warn
perf_duration_work
perf_event_account_interrupt
perf_event_attrs
perf_event_exit_cpu
perf_event_itrace_started
perf_log_lost_samples
perf_pmu_name
perf_sample_event_took
perf_sched_cb_dec
perf_sched_cb_inc
pgd_clear_bad
phy_core_exit
pin_insert
pmac_get_uninorth_variant
pm_generic_prepare
pm_labels
pm_system_cancel_wakeup
power_events_sysfs_show
powerpc_macros
powerpc_num_macros
power_supply_class_exit
prandom_reseed_late
pr_cont_kernfs_name
prep_compound_page
__print_once.21255
print_vma_addr
prof_cpu_mask_proc_fops
prof_cpu_mask_proc_open
prof_cpu_mask_proc_show
prof_cpu_mask_proc_write
ptrace_get_reg
ptrace_writedata
pud_clear_bad
randomize_page
rcu_test_sync_prims
read_bhrb
reclaim_clean_pages_from_list
refined_jiffies
register_refined_jiffies
register_stat_tracer
regs_query_register_name
relay_prepare_cpu
remove_percpu_irq
__report_allowed
__report_avg
reset_node_managed_pages
__reset_stat_session
restore_math
ret_from_standby
ring_buffer_event_time_stamp
ring_buffer_nest_end
ring_buffer_nest_start
ring_buffer_page_len
_rs.53145
rsa_exit
rtc_dev_exit
s2idle_set_ops
save_named_trigger
sched_idle_set_state
sched_setattr_nocheck
scsi_sysfs_unregister
sdio_unregister_bus
secondary_cpu_time_init
send_sig_fault
serial8250_exit
serial_pci_driver_exit
__se_sys_fadvise64_64
__se_sys_gethostname
__se_sys_mmap_pgoff
__se_sys_msgctl
__se_sys_msgget
__se_sys_msgrcv
__se_sys_msgsnd
__se_sys_semctl
__se_sys_semget
__se_sys_semop
__se_sys_semtimedop
__se_sys_shmat
__se_sys_shmctl
__se_sys_shmdt
__se_sys_shmget
__se_sys_sync_file_range
set_breakpoint
set_graph_array
set_iounmap_nonlazy
set_named_trigger_data
set_pci_dma_ops
set_thread_uses_vas
setup_percpu_irq
setup_per_zone_wmarks
sg_pool_exit
shmem_charge
shmem_getpage
shmem_uncharge
shm_file_operations_huge
simple_xattr_list_add
skb_crc32c_csum_help
skb_do_redirect
smpboot_create_threads
smpboot_park_threads
smpboot_unpark_threads
smu_init
snapshot_additional_pages
sort_range
spi_register_board_info
stack_trace_max_lock
stat_dir
stat_seq_next
stat_seq_show
stat_seq_start
stat_seq_stop
subtract_range
swap_buf_le16
swap_lock
sysctl_schedstats
sys_fadvise64_64
sysfs_symlink_target_lock
sys_gethostname
sys_mmap_pgoff
sys_msgctl
sys_msgget
sys_msgrcv
sys_msgsnd
__sysrq_get_key_op
sys_semctl
sys_semget
sys_semop
sys_semtimedop
sys_shmat
sys_shmctl
sys_shmdt
sys_shmget
sys_switch_endian
sys_sync_file_range
tasklist_lock
task_rcu_dereference
__task_rq_lock
tau_interrupts
tcp_fastopen_active_should_disable
tcp_set_ulp_id
tcpudp_mt_exit
tg_set_cfs_period
tg_set_cfs_quota
tick_broadcast_ipi_handler
tick_cancel_sched_timer
tick_freeze
tick_freeze_depth
tick_nohz_get_idle_calls
tick_nohz_get_idle_calls_cpu
tick_nohz_idle_got_tick
tick_nohz_idle_retain_tick
tick_nohz_tick_stopped_cpu
tick_suspend_local
tick_unfreeze
timer_migration_handler
__tlb_remove_page_size
tnum_sbin
tnum_xor
touch_softlockup_watchdog_sync
trace_array_printk
trace_array_printk_buf
trace_array_vprintk
trace_clock_in_ns
trace_find_filtered_pid
tracefs_remove
trace_graph_function
trace_keep_overwrite
trace_latency_header
tracer_init
trace_stat_seq_ops
tracing_is_enabled
tracing_record_tgid
tracing_start
tracing_stat_fops
tracing_stat_open
tracing_stat_release
uart_get_console
udbg_printf
unix_get_socket
unpause_named_trigger
unregister_stat_tracer
uprobe_get_trap_addr
using_ftrace_ops_list_func
vfs_getxattr_alloc
vfs_ioctl
vle_num_opcodes
vle_opcodes
vma_is_special_mapping
vma_is_stack_for_current
vm_numa_stat_key
vsx_unavailable_exception
vwrite
walk_iomem_res_desc
walk_mem_res
walk_system_ram_res
watchdog_dev_exit
watchdog_exit
workqueue_prepare_cpu
wq_update_unbound_numa
x509_key_exit
xt_fini
xtime_update
zone_pcp_reset


> 
> Will send them by private emails.
> 
>> Thanks
>> Christophe
>>
>>
>>>
>>> ---
>>> done
>>> copying OF device tree...
>>> Building dt strings...
>>> Building dt structure...
>>> Device tree strings 0x01100000 -> 0x01100e02
>>> Device tree struct   0x01101000 -> 0x01109000
>>> Quiescing Open Firmware ...
>>> Booting Linux via __start() @ 0x00140000 ...
>>> _
>>> ---
>>>
>>>
>>>
>>>>    config ISA_DMA_API
>>>> --
>>>> 2.13.3
>>>>
>>