[PATCH 1/7] entry: Move exit to usermode functions to header file
From: Sven Schnelle <svens@linux.ibm.com> To allow inlining, move exit_to_user_mode() to entry-common.h. Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20231218074520.1998026-2-svens@linux.ibm.com Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- include/linux/entry-common.h | 53 +++++++++++++++++++++++++++++++++++- kernel/entry/common.c | 52 ++++++----------------------------- 2 files changed, 61 insertions(+), 44 deletions(-) diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index d95ab85f96ba..6a6e98f3805f 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -7,6 +7,10 @@ #include <linux/syscalls.h> #include <linux/seccomp.h> #include <linux/sched.h> +#include <linux/context_tracking.h> +#include <linux/livepatch.h> +#include <linux/resume_user_mode.h> +#include <linux/tick.h> #include <asm/entry-common.h> @@ -258,6 +262,43 @@ static __always_inline void arch_exit_to_user_mode(void) { } */ void arch_do_signal_or_restart(struct pt_regs *regs); +/** + * exit_to_user_mode_loop - do any pending work before leaving to user space + */ +unsigned long exit_to_user_mode_loop(struct pt_regs *regs, + unsigned long ti_work); + +/** + * exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required + * @regs: Pointer to pt_regs on entry stack + * + * 1) check that interrupts are disabled + * 2) call tick_nohz_user_enter_prepare() + * 3) call exit_to_user_mode_loop() if any flags from + * EXIT_TO_USER_MODE_WORK are set + * 4) check that interrupts are still disabled + */ +static __always_inline void exit_to_user_mode_prepare(struct pt_regs *regs) +{ + unsigned long ti_work; + + lockdep_assert_irqs_disabled(); + + /* Flush pending rcuog wakeup before the last need_resched() check */ + tick_nohz_user_enter_prepare(); + + ti_work = read_thread_flags(); + if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK)) + ti_work = exit_to_user_mode_loop(regs, ti_work); + + arch_exit_to_user_mode_prepare(regs, ti_work); + + /* Ensure that kernel state is sane for a return to userspace */ + kmap_assert_nomap(); + lockdep_assert_irqs_disabled(); + lockdep_sys_exit(); +} + /** * exit_to_user_mode - Fixup state when exiting to user mode * @@ -276,7 +317,17 @@ void arch_do_signal_or_restart(struct pt_regs *regs); * non-instrumentable. * The caller has to invoke syscall_exit_to_user_mode_work() before this. */ -void exit_to_user_mode(void); +static __always_inline void exit_to_user_mode(void) +{ + instrumentation_begin(); + trace_hardirqs_on_prepare(); + lockdep_hardirqs_on_prepare(); + instrumentation_end(); + + user_enter_irqoff(); + arch_exit_to_user_mode(); + lockdep_hardirqs_on(CALLER_ADDR0); +} /** * syscall_exit_to_user_mode_work - Handle work before returning to user mode diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 5ff4f1cd3644..bf545a7a5388 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -129,29 +129,16 @@ noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs) instrumentation_end(); } -/* See comment for exit_to_user_mode() in entry-common.h */ -static __always_inline void __exit_to_user_mode(void) -{ - instrumentation_begin(); - trace_hardirqs_on_prepare(); - lockdep_hardirqs_on_prepare(); - instrumentation_end(); - - user_enter_irqoff(); - arch_exit_to_user_mode(); - lockdep_hardirqs_on(CALLER_ADDR0); -} - -void noinstr exit_to_user_mode(void) -{ - __exit_to_user_mode(); -} - /* Workaround to allow gradual conversion of architecture code */ void __weak arch_do_signal_or_restart(struct pt_regs *regs) { } -static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, - unsigned long ti_work) +/** + * exit_to_user_mode_loop - do any pending work before leaving to user space + * @regs: Pointer to pt_regs on entry stack + * @ti_work: TIF work flags as read by the caller + */ +__always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs, + unsigned long ti_work) { /* * Before returning to user space ensure that all pending work @@ -196,27 +183,6 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, return ti_work; } -static void exit_to_user_mode_prepare(struct pt_regs *regs) -{ - unsigned long ti_work; - - lockdep_assert_irqs_disabled(); - - /* Flush pending rcuog wakeup before the last need_resched() check */ - tick_nohz_user_enter_prepare(); - - ti_work = read_thread_flags(); - if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK)) - ti_work = exit_to_user_mode_loop(regs, ti_work); - - arch_exit_to_user_mode_prepare(regs, ti_work); - - /* Ensure that kernel state is sane for a return to userspace */ - kmap_assert_nomap(); - lockdep_assert_irqs_disabled(); - lockdep_sys_exit(); -} - /* * If SYSCALL_EMU is set, then the only reason to report is when * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall @@ -301,7 +267,7 @@ __visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs) instrumentation_begin(); __syscall_exit_to_user_mode_work(regs); instrumentation_end(); - __exit_to_user_mode(); + exit_to_user_mode(); } noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs) @@ -314,7 +280,7 @@ noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs) instrumentation_begin(); exit_to_user_mode_prepare(regs); instrumentation_end(); - __exit_to_user_mode(); + exit_to_user_mode(); } noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs) -- 2.33.0
From: Sven Schnelle <svens@linux.ibm.com> To allow inlining of enter_from_user_mode(), move it to entry-common.h. Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20231218074520.1998026-3-svens@linux.ibm.com Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- include/linux/entry-common.h | 15 ++++++++++++++- kernel/entry/common.c | 26 +++----------------------- 2 files changed, 17 insertions(+), 24 deletions(-) diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index 6a6e98f3805f..c4205390448e 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -11,6 +11,7 @@ #include <linux/livepatch.h> #include <linux/resume_user_mode.h> #include <linux/tick.h> +#include <linux/kmsan.h> #include <asm/entry-common.h> @@ -102,7 +103,19 @@ static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs) {} * done between establishing state and enabling interrupts. The caller must * enable interrupts before invoking syscall_enter_from_user_mode_work(). */ -void enter_from_user_mode(struct pt_regs *regs); +static __always_inline void enter_from_user_mode(struct pt_regs *regs) +{ + arch_enter_from_user_mode(regs); + lockdep_hardirqs_off(CALLER_ADDR0); + + CT_WARN_ON(__ct_state() != CONTEXT_USER); + user_exit_irqoff(); + + instrumentation_begin(); + kmsan_unpoison_entry_regs(regs); + trace_hardirqs_off_finish(); + instrumentation_end(); +} /** * syscall_enter_from_user_mode_prepare - Establish state and enable interrupts diff --git a/kernel/entry/common.c b/kernel/entry/common.c index bf545a7a5388..3c41bc7f5d68 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -15,26 +15,6 @@ #define CREATE_TRACE_POINTS #include <trace/events/syscalls.h> -/* See comment for enter_from_user_mode() in entry-common.h */ -static __always_inline void __enter_from_user_mode(struct pt_regs *regs) -{ - arch_enter_from_user_mode(regs); - lockdep_hardirqs_off(CALLER_ADDR0); - - CT_WARN_ON(__ct_state() != CONTEXT_USER); - user_exit_irqoff(); - - instrumentation_begin(); - kmsan_unpoison_entry_regs(regs); - trace_hardirqs_off_finish(); - instrumentation_end(); -} - -void noinstr enter_from_user_mode(struct pt_regs *regs) -{ - __enter_from_user_mode(regs); -} - static inline void syscall_enter_audit(struct pt_regs *regs, long syscall) { if (unlikely(audit_context())) { @@ -111,7 +91,7 @@ noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall) { long ret; - __enter_from_user_mode(regs); + enter_from_user_mode(regs); instrumentation_begin(); local_irq_enable(); @@ -123,7 +103,7 @@ noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall) noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs) { - __enter_from_user_mode(regs); + enter_from_user_mode(regs); instrumentation_begin(); local_irq_enable(); instrumentation_end(); @@ -272,7 +252,7 @@ __visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs) noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs) { - __enter_from_user_mode(regs); + enter_from_user_mode(regs); } noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs) -- 2.33.0
From: Sven Schnelle <svens@linux.ibm.com> To allow inlining of syscall_enter_from_user_mode(), move it to entry-common.h. Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20231218074520.1998026-4-svens@linux.ibm.com Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- include/linux/entry-common.h | 27 +++++++++++++++++++++++++-- kernel/entry/common.c | 32 +------------------------------- 2 files changed, 26 insertions(+), 33 deletions(-) diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index c4205390448e..b0fb775a600d 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -134,6 +134,9 @@ static __always_inline void enter_from_user_mode(struct pt_regs *regs) */ void syscall_enter_from_user_mode_prepare(struct pt_regs *regs); +long syscall_trace_enter(struct pt_regs *regs, long syscall, + unsigned long work); + /** * syscall_enter_from_user_mode_work - Check and handle work before invoking * a syscall @@ -157,7 +160,15 @@ void syscall_enter_from_user_mode_prepare(struct pt_regs *regs); * ptrace_report_syscall_entry(), __secure_computing(), trace_sys_enter() * 2) Invocation of audit_syscall_entry() */ -long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall); +static __always_inline long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall) +{ + unsigned long work = READ_ONCE(current_thread_info()->syscall_work); + + if (work & SYSCALL_WORK_ENTER) + syscall = syscall_trace_enter(regs, syscall, work); + + return syscall; +} /** * syscall_enter_from_user_mode - Establish state and check and handle work @@ -176,7 +187,19 @@ long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall); * Returns: The original or a modified syscall number. See * syscall_enter_from_user_mode_work() for further explanation. */ -long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall); +static __always_inline long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall) +{ + long ret; + + enter_from_user_mode(regs); + + instrumentation_begin(); + local_irq_enable(); + ret = syscall_enter_from_user_mode_work(regs, syscall); + instrumentation_end(); + + return ret; +} /** * local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable() diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 3c41bc7f5d68..90843cc38588 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -25,7 +25,7 @@ static inline void syscall_enter_audit(struct pt_regs *regs, long syscall) } } -static long syscall_trace_enter(struct pt_regs *regs, long syscall, +long syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long work) { long ret = 0; @@ -71,36 +71,6 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall, return ret ? : syscall; } -static __always_inline long -__syscall_enter_from_user_work(struct pt_regs *regs, long syscall) -{ - unsigned long work = READ_ONCE(current_thread_info()->syscall_work); - - if (work & SYSCALL_WORK_ENTER) - syscall = syscall_trace_enter(regs, syscall, work); - - return syscall; -} - -long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall) -{ - return __syscall_enter_from_user_work(regs, syscall); -} - -noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall) -{ - long ret; - - enter_from_user_mode(regs); - - instrumentation_begin(); - local_irq_enable(); - ret = __syscall_enter_from_user_work(regs, syscall); - instrumentation_end(); - - return ret; -} - noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs) { enter_from_user_mode(regs); -- 2.33.0
From: Yu Ma <yu.ma@intel.com> alloc_fd() has a sanity check inside to make sure the struct file mapping to the allocated fd is NULL. Remove this sanity check since it can be assured by exisitng zero initilization and NULL set when recycling fd. Meanwhile, add likely/unlikely and expand_file() call avoidance to reduce the work under file_lock. Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Yu Ma <yu.ma@intel.com> Link: https://lore.kernel.org/r/20240717145018.3972922-2-yu.ma@intel.com Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- fs/file.c | 33 ++++++++++++++------------------- 1 file changed, 14 insertions(+), 19 deletions(-) diff --git a/fs/file.c b/fs/file.c index f8cf6728c6a0..6f842ce908f9 100644 --- a/fs/file.c +++ b/fs/file.c @@ -500,7 +500,7 @@ static int alloc_fd(unsigned start, unsigned end, unsigned flags) if (fd < files->next_fd) fd = files->next_fd; - if (fd < fdt->max_fds) + if (likely(fd < fdt->max_fds)) fd = find_next_fd(fdt, fd); /* @@ -508,19 +508,21 @@ static int alloc_fd(unsigned start, unsigned end, unsigned flags) * will limit the total number of files that can be opened. */ error = -EMFILE; - if (fd >= end) + if (unlikely(fd >= end)) goto out; - error = expand_files(files, fd); - if (error < 0) - goto out; + if (unlikely(fd >= fdt->max_fds)) { + error = expand_files(files, fd); + if (error < 0) + goto out; - /* - * If we needed to expand the fs array we - * might have blocked - try again. - */ - if (error) - goto repeat; + /* + * If we needed to expand the fs array we + * might have blocked - try again. + */ + if (error) + goto repeat; + } if (start <= files->next_fd) files->next_fd = fd + 1; @@ -531,13 +533,6 @@ static int alloc_fd(unsigned start, unsigned end, unsigned flags) else __clear_close_on_exec(fd, fdt); error = fd; -#if 1 - /* Sanity check */ - if (rcu_access_pointer(fdt->fd[fd]) != NULL) { - printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); - rcu_assign_pointer(fdt->fd[fd], NULL); - } -#endif out: spin_unlock(&files->file_lock); @@ -600,7 +595,7 @@ void fd_install(unsigned int fd, struct file *file) rcu_read_unlock_sched(); spin_lock(&files->file_lock); fdt = files_fdtable(files); - BUG_ON(fdt->fd[fd] != NULL); + WARN_ON(fdt->fd[fd] != NULL); rcu_assign_pointer(fdt->fd[fd], file); spin_unlock(&files->file_lock); return; -- 2.33.0
From: Yu Ma <yu.ma@intel.com> 64 bits in open_fds are mapped to a common bit in full_fds_bits. It is very likely that a bit in full_fds_bits has been cleared before in __clear_open_fds()'s operation. Check the clear bit in full_fds_bits before clearing to avoid unnecessary write and cache bouncing. See commit fc90888d07b8 ("vfs: conditionally clear close-on-exec flag") for a similar optimization. take stock kernel with patch 1 as baseline, it improves pts/blogbench-1.1.0 read for 13%, and write for 5% on Intel ICX 160 cores configuration with v6.10-rc7. Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Yu Ma <yu.ma@intel.com> Link: https://lore.kernel.org/r/20240717145018.3972922-3-yu.ma@intel.com Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- fs/file.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/file.c b/fs/file.c index 6f842ce908f9..32d1aeae00b9 100644 --- a/fs/file.c +++ b/fs/file.c @@ -265,7 +265,9 @@ static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt) static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt) { __clear_bit(fd, fdt->open_fds); - __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits); + fd /= BITS_PER_LONG; + if (test_bit(fd, fdt->full_fds_bits)) + __clear_bit(fd, fdt->full_fds_bits); } /* -- 2.33.0
From: Yu Ma <yu.ma@intel.com> Skip 2-levels searching via find_next_zero_bit() when there is free slot in the word contains next_fd, as: (1) next_fd indicates the lower bound for the first free fd. (2) There is fast path inside of find_next_zero_bit() when size<=64 to speed up searching. (3) After fdt is expanded (the bitmap size doubled for each time of expansion), it would never be shrunk. The search size increases but there are few open fds available here. This fast path is proposed by Mateusz Guzik <mjguzik@gmail.com>, and agreed by Jan Kara <jack@suse.cz>, which is more generic and scalable than previous versions. And on top of patch 1 and 2, it improves pts/blogbench-1.1.0 read by 8% and write by 4% on Intel ICX 160 cores configuration with v6.10-rc7. Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Yu Ma <yu.ma@intel.com> Link: https://lore.kernel.org/r/20240717145018.3972922-4-yu.ma@intel.com Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- fs/file.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/file.c b/fs/file.c index 32d1aeae00b9..64598040ee22 100644 --- a/fs/file.c +++ b/fs/file.c @@ -476,6 +476,15 @@ static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start) unsigned int maxfd = fdt->max_fds; /* always multiple of BITS_PER_LONG */ unsigned int maxbit = maxfd / BITS_PER_LONG; unsigned int bitbit = start / BITS_PER_LONG; + unsigned int bit; + + /* + * Try to avoid looking at the second level bitmap + */ + bit = find_next_zero_bit(&fdt->open_fds[bitbit], BITS_PER_LONG, + start & (BITS_PER_LONG - 1)); + if (bit < BITS_PER_LONG) + return bit + bitbit * BITS_PER_LONG; bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG; if (bitbit >= maxfd) -- 2.33.0
From: Al Viro <viro@zeniv.linux.org.uk> At that point nobody else has references to the victim files_struct; as the matter of fact, the caller will free it immediately after close_files() returns, with no RCU delays or anything of that sort. That's why we are not protecting against fdtable reallocation on expansion, not cleaning the bitmaps, etc. There's no point zeroing the pointers in ->fd[] either, let alone make that an atomic operation. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- fs/file.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/file.c b/fs/file.c index 64598040ee22..27a944e6476c 100644 --- a/fs/file.c +++ b/fs/file.c @@ -419,7 +419,7 @@ static struct fdtable *close_files(struct files_struct * files) set = fdt->open_fds[j++]; while (set) { if (set & 1) { - struct file * file = xchg(&fdt->fd[i], NULL); + struct file *file = fdt->fd[i]; if (file) { filp_close(file, files); cond_resched(); -- 2.33.0
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Zheng Zengkai