kernel/linux.git/lib/vsprintf.c, branch v6.1.2

Merge tag 'printk-for-6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2022-10-10T18:24:19+00:00

Pull printk updates from Petr Mladek: - Initialize pointer hashing using the system workqueue. It avoids taking locks in printk()/vsprintf() code path - Misc code clean up * tag 'printk-for-6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: printk: Mark __printk percpu data ready __ro_after_init printk: Remove bogus comment vs. boot consoles printk: Remove write only variable nr_ext_console_drivers printk: Declare log_wait properly printk: Make pr_flush() static lib/vsprintf: Initialize vsprintf's pointer hash once the random core is ready. lib/vsprintf: Remove static_branch_likely() from __ptr_to_hashval(). lib/vnsprintf: add const modifier for param 'bitmap'

Merge branch 'for-6.1-hash-pointer-init' into for-linus

2022-10-04T13:55:44+00:00

lib/vsprintf: Initialize vsprintf's pointer hash once the random core is ready.

2022-09-29T11:44:51+00:00

The printk code invokes vnsprintf in order to compute the complete string before adding it into its buffer. This happens in an IRQ-off region which leads to a warning on PREEMPT_RT in the random code if the format strings contains a %p for pointer printing. This happens because the random core acquires locks which become sleeping locks on PREEMPT_RT which must not be acquired with disabled interrupts and or preemption disabled. By default the pointers are hashed which requires a random value on the first invocation (either by printk or another user which comes first. One could argue that there is no need for printk to disable interrupts during the vsprintf() invocation which would fix the just mentioned problem. However printk itself can be invoked in a context with disabled interrupts which would lead to the very same problem. Move the initialization of ptr_key into a worker and schedule it from subsys_initcall(). This happens early but after the workqueue subsystem is ready. Use get_random_bytes() to retrieve the random value if the RNG core is ready, otherwise schedule a worker in two seconds and try again. Another advantage is that it removes a lock from the vsprintf() code path. It prevents a possible deadlock when printk("%p", ptr) is called under the lock taken in get_random_bytes(). Reported-by: Mike Galbraith Signed-off-by: Sebastian Andrzej Siewior Acked-by: Jason A. Donenfeld Reviewed-by: Petr Mladek [pmladek@suse.com: Added a note about the it prevented a possible deadlock in printk().] Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220927104912.622645-3-bigeasy@linutronix.de

lib/vsprintf: Remove static_branch_likely() from __ptr_to_hashval().

2022-09-29T11:44:27+00:00

Using static_branch_likely() to signal that ptr_key has been filled is a bit much given that it is not a fast path. Replace static_branch_likely() with bool for condition and a memory barrier for ptr_key. Suggested-by: Petr Mladek Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220927104912.622645-2-bigeasy@linutronix.de

vsprintf: add new `%pA` format specifier

2022-09-28T07:00:20+00:00

This patch adds a format specifier `%pA` to `vsprintf` which formats a pointer as `core::fmt::Arguments`. Doing so allows us to directly format to the internal buffer of `printf`, so we do not have to use a temporary buffer on the stack to pre-assemble the message on the Rust side. This specifier is intended only to be used from Rust and not for C, so `checkpatch.pl` is intentionally unchanged to catch any misuse. Reviewed-by: Kees Cook Acked-by: Petr Mladek Reviewed-by: Greg Kroah-Hartman Co-developed-by: Alex Gaynor Signed-off-by: Alex Gaynor Co-developed-by: Wedson Almeida Filho Signed-off-by: Wedson Almeida Filho Signed-off-by: Gary Guo Co-developed-by: Miguel Ojeda Signed-off-by: Miguel Ojeda

lib/vnsprintf: add const modifier for param 'bitmap'

2022-08-25T08:09:03+00:00

There is no modification for param bitmap in function bitmap_string() and bitmap_list_string(), so add const modifier for it. Signed-off-by: Jian Shen Signed-off-by: Guangbin Huang Reviewed-by: Steven Rostedt (Google) Reviewed-by: Sergey Senozhatsky Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20220816144557.30779-1-huangguangbin2@huawei.com

random: remove rng_has_arch_random()

2022-06-10T09:29:48+00:00

With arch randomness being used by every distro and enabled in defconfigs, the distinction between rng_has_arch_random() and rng_is_initialized() is now rather small. In fact, the places where they differ are now places where paranoid users and system builders really don't want arch randomness to be used, in which case we should respect that choice, or places where arch randomness is known to be broken, in which case that choice is all the more important. So this commit just removes the function and its one user. Reviewed-by: Petr Mladek # for vsprintf.c Signed-off-by: Jason A. Donenfeld

random: remove mostly unused async readiness notifier

2022-05-19T14:54:15+00:00

The register_random_ready_notifier() notifier is somewhat complicated, and was already recently rewritten to use notifier blocks. It is only used now by one consumer in the kernel, vsprintf.c, for which the async mechanism is really overly complex for what it actually needs. This commit removes register_random_ready_notifier() and unregister_random_ ready_notifier(), because it just adds complication with little utility, and changes vsprintf.c to just check on `!rng_is_initialized() && !rng_has_arch_random()`, which will eventually be true. Performance- wise, that code was already using a static branch, so there's basically no overhead at all to this change. Cc: Steven Rostedt Cc: Sergey Senozhatsky Acked-by: Petr Mladek # for vsprintf.c Reviewed-by: Petr Mladek Signed-off-by: Jason A. Donenfeld

random: remove get_random_bytes_arch() and add rng_has_arch_random()

2022-05-19T14:54:15+00:00

The RNG incorporates RDRAND into its state at boot and every time it reseeds, so there's no reason for callers to use it directly. The hashing that the RNG does on it is preferable to using the bytes raw. The only current use case of get_random_bytes_arch() is vsprintf's siphash key for pointer hashing, which uses it to initialize the pointer secret earlier than usual if RDRAND is available. In order to replace this narrow use case, just expose whether RDRAND is mixed into the RNG, with a new function called rng_has_arch_random(). With that taken care of, there are no users of get_random_bytes_arch() left, so it can be removed. Later, if trust_cpu gets turned on by default (as most distros are doing), this one use of rng_has_arch_random() can probably go away as well. Cc: Steven Rostedt Cc: Sergey Senozhatsky Acked-by: Petr Mladek # for vsprintf.c Signed-off-by: Jason A. Donenfeld

lib/vsprintf: avoid redundant work with 0 size

2022-03-25T02:06:44+00:00

Patch series "mm/page_owner: Extend page_owner to show memcg information", v4. While debugging the constant increase in percpu memory consumption on a system that spawned large number of containers, it was found that a lot of offline mem_cgroup structures remained in place without being freed. Further investigation indicated that those mem_cgroup structures were pinned by some pages. In order to find out what those pages are, the existing page_owner debugging tool is extended to show memory cgroup information and whether those memcgs are offline or not. With the enhanced page_owner tool, the following is a typical page that pinned the mem_cgroup structure in my test case: Page allocated via order 0, mask 0x1100cca(GFP_HIGHUSER_MOVABLE), pid 162970 (podman), ts 1097761405537 ns, free_ts 1097760838089 ns PFN 1925700 type Movable Block 3761 type Movable Flags 0x17ffffc00c001c(uptodate|dirty|lru|reclaim|swapbacked|node=0|zone=2|lastcpupid=0x1fffff) prep_new_page+0xac/0xe0 get_page_from_freelist+0x1327/0x14d0 __alloc_pages+0x191/0x340 alloc_pages_vma+0x84/0x250 shmem_alloc_page+0x3f/0x90 shmem_alloc_and_acct_page+0x76/0x1c0 shmem_getpage_gfp+0x281/0x940 shmem_write_begin+0x36/0xe0 generic_perform_write+0xed/0x1d0 __generic_file_write_iter+0xdc/0x1b0 generic_file_write_iter+0x5d/0xb0 new_sync_write+0x11f/0x1b0 vfs_write+0x1ba/0x2a0 ksys_write+0x59/0xd0 do_syscall_64+0x37/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae Charged to offline memcg libpod-conmon-15e4f9c758422306b73b2dd99f9d50a5ea53cbb16b4a13a2c2308a4253cc0ec8. So the page was not freed because it was part of a shmem segment. That is useful information that can help users to diagnose similar problems. With cgroup v1, /proc/cgroups can be read to find out the total number of memory cgroups (online + offline). With cgroup v2, the cgroup.stat of the root cgroup can be read to find the number of dying cgroups (most likely pinned by dying memcgs). The page_owner feature is not supposed to be enabled for production system due to its memory overhead. However, if it is suspected that dying memcgs are increasing over time, a test environment with page_owner enabled can then be set up with appropriate workload for further analysis on what may be causing the increasing number of dying memcgs. This patch (of 4): For *scnprintf(), vsnprintf() is always called even if the input size is 0. That is a waste of time, so just return 0 in this case. Note that vsnprintf() will never return -1 to indicate an error. So skipping the call to vsnprintf() when size is 0 will have no functional impact at all. Link: https://lkml.kernel.org/r/20220202203036.744010-1-longman@redhat.com Link: https://lkml.kernel.org/r/20220202203036.744010-2-longman@redhat.com Signed-off-by: Waiman Long Acked-by: David Rientjes Reviewed-by: Sergey Senozhatsky Acked-by: Roman Gushchin Acked-by: Rafael Aquini Acked-by: Mike Rapoport Cc: Roman Gushchin Cc: Johannes Weiner Cc: Michal Hocko Cc: Vladimir Davydov Cc: Petr Mladek Cc: Steven Rostedt (Google) Cc: Andy Shevchenko Cc: Rasmus Villemoes Cc: Ira Weiny Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds