From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- arch/alpha/lib/memchr.S | 165 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 165 insertions(+) create mode 100644 arch/alpha/lib/memchr.S (limited to 'arch/alpha/lib/memchr.S') diff --git a/arch/alpha/lib/memchr.S b/arch/alpha/lib/memchr.S new file mode 100644 index 000000000..45366e32f --- /dev/null +++ b/arch/alpha/lib/memchr.S @@ -0,0 +1,165 @@ +/* Copyright (C) 1996 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by David Mosberger (davidm@cs.arizona.edu). + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public License as + published by the Free Software Foundation; either version 2 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +/* Finds characters in a memory area. Optimized for the Alpha: + + - memory accessed as aligned quadwords only + - uses cmpbge to compare 8 bytes in parallel + - does binary search to find 0 byte in last + quadword (HAKMEM needed 12 instructions to + do this instead of the 9 instructions that + binary search needs). + +For correctness consider that: + + - only minimum number of quadwords may be accessed + - the third argument is an unsigned long +*/ +#include + .set noreorder + .set noat + + .globl memchr + .ent memchr +memchr: + .frame $30,0,$26,0 + .prologue 0 + + # Hack -- if someone passes in (size_t)-1, hoping to just + # search til the end of the address space, we will overflow + # below when we find the address of the last byte. Given + # that we will never have a 56-bit address space, cropping + # the length is the easiest way to avoid trouble. + zap $18, 0x80, $5 #-e0 : + + beq $18, $not_found # .. e1 : + ldq_u $1, 0($16) # e1 : load first quadword + insbl $17, 1, $2 # .. e0 : $2 = 000000000000ch00 + and $17, 0xff, $17 #-e0 : $17 = 00000000000000ch + cmpult $18, 9, $4 # .. e1 : + or $2, $17, $17 # e0 : $17 = 000000000000chch + lda $3, -1($31) # .. e1 : + sll $17, 16, $2 #-e0 : $2 = 00000000chch0000 + addq $16, $5, $5 # .. e1 : + or $2, $17, $17 # e1 : $17 = 00000000chchchch + unop # : + sll $17, 32, $2 #-e0 : $2 = chchchch00000000 + or $2, $17, $17 # e1 : $17 = chchchchchchchch + extql $1, $16, $7 # e0 : + beq $4, $first_quad # .. e1 : + + ldq_u $6, -1($5) #-e1 : eight or less bytes to search + extqh $6, $16, $6 # .. e0 : + mov $16, $0 # e0 : + or $7, $6, $1 # .. e1 : $1 = quadword starting at $16 + + # Deal with the case where at most 8 bytes remain to be searched + # in $1. E.g.: + # $18 = 6 + # $1 = ????c6c5c4c3c2c1 +$last_quad: + negq $18, $6 #-e0 : + xor $17, $1, $1 # .. e1 : + srl $3, $6, $6 # e0 : $6 = mask of $18 bits set + cmpbge $31, $1, $2 # .. e1 : + and $2, $6, $2 #-e0 : + beq $2, $not_found # .. e1 : + +$found_it: + # Now, determine which byte matched: + negq $2, $3 # e0 : + and $2, $3, $2 # e1 : + + and $2, 0x0f, $1 #-e0 : + addq $0, 4, $3 # .. e1 : + cmoveq $1, $3, $0 # e0 : + + addq $0, 2, $3 # .. e1 : + and $2, 0x33, $1 #-e0 : + cmoveq $1, $3, $0 # .. e1 : + + and $2, 0x55, $1 # e0 : + addq $0, 1, $3 # .. e1 : + cmoveq $1, $3, $0 #-e0 : + +$done: ret # .. e1 : + + # Deal with the case where $18 > 8 bytes remain to be + # searched. $16 may not be aligned. + .align 4 +$first_quad: + andnot $16, 0x7, $0 #-e1 : + insqh $3, $16, $2 # .. e0 : $2 = 0000ffffffffffff ($16<0:2> ff) + xor $1, $17, $1 # e0 : + or $1, $2, $1 # e1 : $1 = ====ffffffffffff + cmpbge $31, $1, $2 #-e0 : + bne $2, $found_it # .. e1 : + + # At least one byte left to process. + + ldq $1, 8($0) # e0 : + subq $5, 1, $18 # .. e1 : + addq $0, 8, $0 #-e0 : + + # Make $18 point to last quad to be accessed (the + # last quad may or may not be partial). + + andnot $18, 0x7, $18 # .. e1 : + cmpult $0, $18, $2 # e0 : + beq $2, $final # .. e1 : + + # At least two quads remain to be accessed. + + subq $18, $0, $4 #-e0 : $4 <- nr quads to be processed + and $4, 8, $4 # e1 : odd number of quads? + bne $4, $odd_quad_count # e1 : + + # At least three quads remain to be accessed + + mov $1, $4 # e0 : move prefetched value to correct reg + + .align 4 +$unrolled_loop: + ldq $1, 8($0) #-e0 : prefetch $1 + xor $17, $4, $2 # .. e1 : + cmpbge $31, $2, $2 # e0 : + bne $2, $found_it # .. e1 : + + addq $0, 8, $0 #-e0 : +$odd_quad_count: + xor $17, $1, $2 # .. e1 : + ldq $4, 8($0) # e0 : prefetch $4 + cmpbge $31, $2, $2 # .. e1 : + addq $0, 8, $6 #-e0 : + bne $2, $found_it # .. e1 : + + cmpult $6, $18, $6 # e0 : + addq $0, 8, $0 # .. e1 : + bne $6, $unrolled_loop #-e1 : + + mov $4, $1 # e0 : move prefetched value into $1 +$final: subq $5, $0, $18 # .. e1 : $18 <- number of bytes left to do + bne $18, $last_quad # e1 : + +$not_found: + mov $31, $0 #-e0 : + ret # .. e1 : + + .end memchr + EXPORT_SYMBOL(memchr) -- cgit v1.3.1