kernel/linux.git/include/asm-generic/bug.h, branch v4.4.193

asm-generic: default BUG_ON(x) to if(x)BUG()

2019-08-25T08:53:04+00:00

commit 3c047057d1206ec0f3b88c7809cacba478067a0c upstream. When CONFIG_BUG is disabled, BUG_ON() will only evaluate the condition, but will not actually stop the current thread. GCC warns about a couple of BUG_ON() users where this actually leads to further undefined behavior: include/linux/ceph/osdmap.h: In function 'ceph_can_shift_osds': include/linux/ceph/osdmap.h:54:1: warning: control reaches end of non-void function fs/ext4/inode.c: In function 'ext4_map_blocks': fs/ext4/inode.c:548:5: warning: 'retval' may be used uninitialized in this function drivers/mfd/db8500-prcmu.c: In function 'prcmu_config_clkout': drivers/mfd/db8500-prcmu.c:762:10: warning: 'div_mask' may be used uninitialized in this function drivers/mfd/db8500-prcmu.c:769:13: warning: 'mask' may be used uninitialized in this function drivers/mfd/db8500-prcmu.c:757:7: warning: 'bits' may be used uninitialized in this function drivers/tty/serial/8250/8250_core.c: In function 'univ8250_release_irq': drivers/tty/serial/8250/8250_core.c:252:18: warning: 'i' may be used uninitialized in this function drivers/tty/serial/8250/8250_core.c:235:19: note: 'i' was declared here There is an obvious conflict of interest here: on the one hand, someone who disables CONFIG_BUG() will want the kernel to be as small as possible and doesn't care about printing error messages to a console that nobody looks at. On the other hand, running into a BUG_ON() condition means that something has gone wrong, and we probably want to also stop doing things that might cause data corruption. This patch picks the second choice, and changes the NOP to BUG(), which normally stops the execution of the current thread in some form (endless loop or a trap). This follows the logic we applied in a4b5d580e078 ("bug: Make BUG() always stop the machine"). For ARM multi_v7_defconfig, the size slightly increases: section CONFIG_BUG=y CONFIG_BUG=n CONFIG_BUG=n+patch .text 8320248 | 8180944 | 8207688 .rodata 3633720 | 3567144 | 3570648 __bug_table 32508 | --- | --- __modver 692 | 1584 | 2176 .init.text 558132 | 548300 | 550088 .exit.text 12380 | 12256 | 12380 .data 1016672 | 1016064 | 1016128 Total 14622556 | 14374510 | 14407326 So instead of saving 1.70% of the total image size, we only save 1.48% by turning off CONFIG_BUG, but in return we can ensure that we don't run into cases of uninitialized variable or return code uses when something bad happens. Aside from that, we significantly reduce the number of warnings in randconfig builds, which makes it easier to fix the warnings about other problems. Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman

bug.h: work around GCC PR82365 in BUG()

2019-07-10T07:56:42+00:00

[ Upstream commit 173a3efd3edb2ef6ef07471397c5f542a360e9c1 ] Looking at functions with large stack frames across all architectures led me discovering that BUG() suffers from the same problem as fortify_panic(), which I've added a workaround for already. In short, variables that go out of scope by calling a noreturn function or __builtin_unreachable() keep using stack space in functions afterwards. A workaround that was identified is to insert an empty assembler statement just before calling the function that doesn't return. I'm adding a macro "barrier_before_unreachable()" to document this, and insert calls to that in all instances of BUG() that currently suffer from this problem. The files that saw the largest change from this had these frame sizes before, and much less with my patch: fs/ext4/inode.c:82:1: warning: the frame size of 1672 bytes is larger than 800 bytes [-Wframe-larger-than=] fs/ext4/namei.c:434:1: warning: the frame size of 904 bytes is larger than 800 bytes [-Wframe-larger-than=] fs/ext4/super.c:2279:1: warning: the frame size of 1160 bytes is larger than 800 bytes [-Wframe-larger-than=] fs/ext4/xattr.c:146:1: warning: the frame size of 1168 bytes is larger than 800 bytes [-Wframe-larger-than=] fs/f2fs/inode.c:152:1: warning: the frame size of 1424 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_core.c:1195:1: warning: the frame size of 1068 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_core.c:395:1: warning: the frame size of 1084 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_ftp.c:298:1: warning: the frame size of 928 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_ftp.c:418:1: warning: the frame size of 908 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_lblcr.c:718:1: warning: the frame size of 960 bytes is larger than 800 bytes [-Wframe-larger-than=] drivers/net/xen-netback/netback.c:1500:1: warning: the frame size of 1088 bytes is larger than 800 bytes [-Wframe-larger-than=] In case of ARC and CRIS, it turns out that the BUG() implementation actually does return (or at least the compiler thinks it does), resulting in lots of warnings about uninitialized variable use and leaving noreturn functions, such as: block/cfq-iosched.c: In function 'cfq_async_queue_prio': block/cfq-iosched.c:3804:1: error: control reaches end of non-void function [-Werror=return-type] include/linux/dmaengine.h: In function 'dma_maxpq': include/linux/dmaengine.h:1123:1: error: control reaches end of non-void function [-Werror=return-type] This makes them call __builtin_trap() instead, which should normally dump the stack and kill the current process, like some of the other architectures already do. I tried adding barrier_before_unreachable() to panic() and fortify_panic() as well, but that had very little effect, so I'm not submitting that patch. Vineet said: : For ARC, it is double win. : : 1. Fixes 3 -Wreturn-type warnings : : | ../net/core/ethtool.c:311:1: warning: control reaches end of non-void function : [-Wreturn-type] : | ../kernel/sched/core.c:3246:1: warning: control reaches end of non-void function : [-Wreturn-type] : | ../include/linux/sunrpc/svc_xprt.h:180:1: warning: control reaches end of : non-void function [-Wreturn-type] : : 2. bloat-o-meter reports code size improvements as gcc elides the : generated code for stack return. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365 Link: http://lkml.kernel.org/r/20171219114112.939391-1-arnd@arndb.de Signed-off-by: Arnd Bergmann Acked-by: Vineet Gupta [arch/arc] Tested-by: Vineet Gupta [arch/arc] Cc: Mikael Starvik Cc: Jesper Nilsson Cc: Tony Luck Cc: Fenghua Yu Cc: Geert Uytterhoeven Cc: "David S. Miller" Cc: Christopher Li Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Kees Cook Cc: Ingo Molnar Cc: Josh Poimboeuf Cc: Will Deacon Cc: "Steven Rostedt (VMware)" Cc: Mark Rutland Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin [ removed cris changes - gregkh] Signed-off-by: Greg Kroah-Hartman

bug: Make BUG() always stop the machine

2014-04-07T23:36:10+00:00

When !CONFIG_BUG and !HAVE_ARCH_BUG, define the generic BUG() as an infinite loop rather than a no-op. This avoids undefined behavior if execution ever actually reaches BUG(), and avoids warnings about code after BUG() (such as on non-void functions calling BUG() and then not returning). bloat-o-meter results: add/remove: 0/0 grow/shrink: 43/10 up/down: 235/-98 (137) function old new delta umount_collect 119 138 +19 notify_change 306 324 +18 xstate_enable_boot_cpu 252 269 +17 kunmap 54 70 +16 balloon_page_dequeue 112 126 +14 mm_take_all_locks 223 233 +10 list_lru_walk_node 143 152 +9 vma_adjust 1059 1067 +8 pcpu_setup_first_chunk 1130 1138 +8 mm_drop_all_locks 143 151 +8 ns_capable 55 62 +7 anon_transport_class_unregister 8 15 +7 srcu_init_notifier_head 35 41 +6 shrink_dcache_for_umount 174 180 +6 kunmap_high 99 105 +6 end_page_writeback 43 49 +6 do_exit 1339 1345 +6 __kfifo_dma_out_prepare_r 86 92 +6 __kfifo_dma_in_prepare_r 90 96 +6 fixup_user_fault 120 125 +5 repair_env_string 73 77 +4 read_cache_pages_invalidate_page 56 60 +4 isolate_lru_pages.isra 142 146 +4 do_notify_parent_cldstop 255 259 +4 cpu_init 370 374 +4 utimes_common 270 272 +2 tasklet_hi_action 91 93 +2 tasklet_action 91 93 +2 set_pte_vaddr 46 48 +2 find_get_pages_tag 202 204 +2 early_iounmap 185 187 +2 __native_set_fixmap 36 38 +2 __get_user_pages 822 824 +2 __early_ioremap 299 301 +2 yield_task_stop 1 2 +1 tick_resume 37 38 +1 switched_to_stop 1 2 +1 switched_to_idle 1 2 +1 prio_changed_stop 1 2 +1 prio_changed_idle 1 2 +1 pm_qos_power_read 111 112 +1 arch_cpu_idle_dead 1 2 +1 __insert_vmap_area 140 141 +1 sys_renameat 614 612 -2 mm_fault_error 297 295 -2 SyS_renameat 614 612 -2 sys_linkat 416 413 -3 SyS_linkat 416 413 -3 chmod_common 129 122 -7 proc_cap_handler 240 225 -15 __schedule 849 831 -18 sys_madvise 1077 1054 -23 SyS_madvise 1077 1054 -23 Signed-off-by: Josh Triplett Reported-by: Arnd Bergmann Acked-by: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

bug: when !CONFIG_BUG, make WARN call no_printk to check format and args

2014-04-07T23:36:10+00:00

The stub version of WARN for !CONFIG_BUG completely ignored its format string and subsequent arguments; make it check them instead, using no_printk. Signed-off-by: Josh Triplett Reported-by: Arnd Bergmann Acked-by: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

include/asm-generic/bug.h: style fix: s/while(0)/while (0)/

2014-04-07T23:36:10+00:00

Signed-off-by: Josh Triplett Reported-by: Randy Dunlap Acked-by: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

bug: when !CONFIG_BUG, simplify WARN_ON_ONCE and family

2014-04-07T23:36:10+00:00

When !CONFIG_BUG, WARN_ON and family become simple passthroughs of their condition argument; however, WARN_ON_ONCE and family still have conditions and a boolean to detect one-time invocation, even though the warning they'd emit doesn't exist. Make the existing definitions conditional on CONFIG_BUG, and add definitions for !CONFIG_BUG that map to the passthrough versions of WARN and WARN_ON. This saves 4.4k on a minimized configuration (smaller than allnoconfig), and 20.6k with defconfig plus CONFIG_BUG=n. Signed-off-by: Josh Triplett Acked-by: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

bug.h: Fix up CONFIG_BUG=n implicit function declarations.

2012-06-25T17:32:49+00:00

Commit 2603efa31a03 ("bug.h: Fix up powerpc build regression") corrected the powerpc build case and extended the __ASSEMBLY__ guards, but it also got caught in pre-processor hell accidentally matching the else case of CONFIG_BUG resulting in the BUG disabled case tripping up on -Werror=implicit-function-declaration. It's not possible to __ASSEMBLY__ guard the entire file as architecture code needs to get at the BUGFLAG_WARNING definition in the GENERIC_BUG case, but the rest of the CONFIG_BUG=y/n case needs to be guarded. Rather than littering endless __ASSEMBLY__ checks in each of the if/else cases we just move the BUGFLAG definitions up under their own GENERIC_BUG test and then shove everything else under one big __ASSEMBLY__ guard. Build tested on all of x86 CONFIG_BUG=y, CONFIG_BUG=n, powerpc (due to it's dependence on BUGFLAG definitions in assembly code), and sh (due to not bringing in linux/kernel.h to satisfy the taint flag definitions used by the generic bug code). Hopefully that's the end of the corner cases and I can abstain from ever having to touch this infernal header ever again. Reported-by: Fengguang Wu Tested-by: Fengguang Wu Acked-by: Randy Dunlap Cc: Arnd Bergmann Signed-off-by: Paul Mundt Signed-off-by: Linus Torvalds

bug.h: Fix up powerpc build regression.

2012-06-18T18:10:59+00:00

The asm-generic/bug.h __ASSEMBLY__ guarding is completely bogus, which tripped up the powerpc build when the kernel.h include was added: In file included from include/asm-generic/bug.h:5:0, from arch/powerpc/include/asm/bug.h:127, from arch/powerpc/kernel/head_64.S:31: include/linux/kernel.h:44:0: warning: "ALIGN" redefined [enabled by default] include/linux/linkage.h:57:0: note: this is the location of the previous definition include/linux/sysinfo.h: Assembler messages: include/linux/sysinfo.h:7: Error: Unrecognized opcode: `struct' include/linux/sysinfo.h:8: Error: Unrecognized opcode: `__kernel_long_t' Moving the __ASSEMBLY__ guard up and stashing the kernel.h include under it fixes this up, as well as covering the case the original fix was attempting to handle. Tested-by: Stephen Rothwell Acked-by: Arnd Bergmann Signed-off-by: Paul Mundt Signed-off-by: Linus Torvalds

bug.h: need linux/kernel.h for TAINT_WARN.

2012-06-11T05:29:58+00:00

asm-generic/bug.h uses taint flags that are only defined in linux/kernel.h, resulting in build failures on platforms that don't include linux/kernel.h some other way: arch/sh/include/asm/thread_info.h:172:2: error: 'TAINT_WARN' undeclared (first use in this function) Caused by commit edd63a2763bd ("set_restore_sigmask() is never called without SIGPENDING (and never should be)"). Reported-by: Stephen Rothwell Cc: Al Viro Signed-off-by: Paul Mundt

consolidate WARN_...ONCE() static variables

2012-03-23T23:58:31+00:00

Due to the alignment of following variables, these typically consume more than just the single byte that 'bool' requires, and as there are a few hundred instances, the cache pollution (not so much the waste of memory) sums up. Put these variables into their own section, outside of any half way frequently used memory range. Do the same also to the __warned variable of rcu_lockdep_assert(). (Don't, however, include the ones used by printk_once() and alike, as they can potentially be hot.) Signed-off-by: Jan Beulich Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds