1 // SPDX-License-Identifier: GPL-2.0 2 3 /* Do not include this file directly. */ 4 5 #ifndef _TRACE_INTERNAL_PID_LIST_H 6 #define _TRACE_INTERNAL_PID_LIST_H 7 8 /* 9 * In order to keep track of what pids to trace, a tree is created much 10 * like page tables are used. This creates a sparse bit map, where 11 * the tree is filled in when needed. A PID is at most 30 bits (see 12 * linux/thread.h), and is broken up into 3 sections based on the bit map 13 * of the bits. The 8 MSB is the "upper1" section. The next 8 MSB is the 14 * "upper2" section and the 14 LSB is the "lower" section. 15 * 16 * A trace_pid_list structure holds the "upper1" section, in an 17 * array of 256 pointers (1 or 2K in size) to "upper_chunk" unions, where 18 * each has an array of 256 pointers (1 or 2K in size) to the "lower_chunk" 19 * structures, where each has an array of size 2K bytes representing a bitmask 20 * of the 14 LSB of the PID (256 * 8 = 2048) 21 * 22 * When a trace_pid_list is allocated, it includes the 256 pointer array 23 * of the upper1 unions. Then a "cache" of upper and lower is allocated 24 * where these will be assigned as needed. 25 * 26 * When a bit is set in the pid_list bitmask, the pid to use has 27 * the 8 MSB masked, and this is used to index the array in the 28 * pid_list to find the next upper union. If the element is NULL, 29 * then one is retrieved from the upper_list cache. If none is 30 * available, then -ENOMEM is returned. 31 * 32 * The next 8 MSB is used to index into the "upper2" section. If this 33 * element is NULL, then it is retrieved from the lower_list cache. 34 * Again, if one is not available -ENOMEM is returned. 35 * 36 * Finally the 14 LSB of the PID is used to set the bit in the 16384 37 * bitmask (made up of 2K bytes). 38 * 39 * When the second upper section or the lower section has their last 40 * bit cleared, they are added back to the free list to be reused 41 * when needed. 42 */ 43 44 #define UPPER_BITS 8 45 #define UPPER_MAX (1 << UPPER_BITS) 46 #define UPPER1_SIZE (1 << UPPER_BITS) 47 #define UPPER2_SIZE (1 << UPPER_BITS) 48 49 #define LOWER_BITS 14 50 #define LOWER_MAX (1 << LOWER_BITS) 51 #define LOWER_SIZE (LOWER_MAX / BITS_PER_LONG) 52 53 #define UPPER1_SHIFT (LOWER_BITS + UPPER_BITS) 54 #define UPPER2_SHIFT LOWER_BITS 55 #define LOWER_MASK (LOWER_MAX - 1) 56 57 #define UPPER_MASK (UPPER_MAX - 1) 58 59 /* According to linux/thread.h pids can not be bigger than or equal to 1 << 30 */ 60 #define MAX_PID (1 << 30) 61 62 /* Just keep 6 chunks of both upper and lower in the cache on alloc */ 63 #define CHUNK_ALLOC 6 64 65 /* Have 2 chunks free, trigger a refill of the cache */ 66 #define CHUNK_REALLOC 2 67 68 union lower_chunk { 69 union lower_chunk *next; 70 unsigned long data[LOWER_SIZE]; // 2K in size 71 }; 72 73 union upper_chunk { 74 union upper_chunk *next; 75 union lower_chunk *data[UPPER2_SIZE]; // 1 or 2K in size 76 }; 77 78 struct trace_pid_list { 79 raw_spinlock_t lock; 80 struct irq_work refill_irqwork; 81 union upper_chunk *upper[UPPER1_SIZE]; // 1 or 2K in size 82 union upper_chunk *upper_list; 83 union lower_chunk *lower_list; 84 int free_upper_chunks; 85 int free_lower_chunks; 86 }; 87 88 #endif /* _TRACE_INTERNAL_PID_LIST_H */ 89