1# SPDX-License-Identifier: GPL-2.0 2menu "Kernel hacking" 3 4source "lib/Kconfig.debug" 5 6config DEBUG_VERBOSE 7 bool "Verbose fault messages" 8 default y 9 select PRINTK 10 help 11 When a program crashes due to an exception, or the kernel detects 12 an internal error, the kernel can print a not so brief message 13 explaining what the problem was. This debugging information is 14 useful to developers and kernel hackers when tracking down problems, 15 but mostly meaningless to other people. This is always helpful for 16 debugging but serves no purpose on a production system. 17 Most people should say N here. 18 19config DEBUG_MMRS 20 tristate "Generate Blackfin MMR tree" 21 depends on !PINCTRL 22 select DEBUG_FS 23 help 24 Create a tree of Blackfin MMRs via the debugfs tree. If 25 you enable this, you will find all MMRs laid out in the 26 /sys/kernel/debug/blackfin/ directory where you can read/write 27 MMRs directly from userspace. This is obviously just a debug 28 feature. 29 30config DEBUG_HWERR 31 bool "Hardware error interrupt debugging" 32 depends on DEBUG_KERNEL 33 help 34 When enabled, the hardware error interrupt is never disabled, and 35 will happen immediately when an error condition occurs. This comes 36 at a slight cost in code size, but is necessary if you are getting 37 hardware error interrupts and need to know where they are coming 38 from. 39 40config EXACT_HWERR 41 bool "Try to make Hardware errors exact" 42 depends on DEBUG_HWERR 43 help 44 By default, the Blackfin hardware errors are not exact - the error 45 be reported multiple cycles after the error happens. This delay 46 can cause the wrong application, or even the kernel to receive a 47 signal to be killed. If you are getting HW errors in your system, 48 try turning this on to ensure they are at least coming from the 49 proper thread. 50 51 On production systems, it is safe (and a small optimization) to say N. 52 53config DEBUG_DOUBLEFAULT 54 bool "Debug Double Faults" 55 default n 56 help 57 If an exception is caused while executing code within the exception 58 handler, the NMI handler, the reset vector, or in emulator mode, 59 a double fault occurs. On the Blackfin, this is a unrecoverable 60 event. You have two options: 61 - RESET exactly when double fault occurs. The excepting 62 instruction address is stored in RETX, where the next kernel 63 boot will print it out. 64 - Print debug message. This is much more error prone, although 65 easier to handle. It is error prone since: 66 - The excepting instruction is not committed. 67 - All writebacks from the instruction are prevented. 68 - The generated exception is not taken. 69 - The EXCAUSE field is updated with an unrecoverable event 70 The only way to check this is to see if EXCAUSE contains the 71 unrecoverable event value at every exception return. By selecting 72 this option, you are skipping over the faulting instruction, and 73 hoping things stay together enough to print out a debug message. 74 75 This does add a little kernel code, but is the only method to debug 76 double faults - if unsure say "Y" 77 78choice 79 prompt "Double Fault Failure Method" 80 default DEBUG_DOUBLEFAULT_PRINT 81 depends on DEBUG_DOUBLEFAULT 82 83config DEBUG_DOUBLEFAULT_PRINT 84 bool "Print" 85 86config DEBUG_DOUBLEFAULT_RESET 87 bool "Reset" 88 89endchoice 90 91config DEBUG_HUNT_FOR_ZERO 92 bool "Catch NULL pointer reads/writes" 93 default y 94 help 95 Say Y here to catch reads/writes to anywhere in the memory range 96 from 0x0000 - 0x0FFF (the first 4k) of memory. This is useful in 97 catching common programming errors such as NULL pointer dereferences. 98 99 Misbehaving applications will be killed (generate a SEGV) while the 100 kernel will trigger a panic. 101 102 Enabling this option will take up an extra entry in CPLB table. 103 Otherwise, there is no extra overhead. 104 105config DEBUG_BFIN_HWTRACE_ON 106 bool "Turn on Blackfin's Hardware Trace" 107 default y 108 help 109 All Blackfins include a Trace Unit which stores a history of the last 110 16 changes in program flow taken by the program sequencer. The history 111 allows the user to recreate the program sequencer’s recent path. This 112 can be handy when an application dies - we print out the execution 113 path of how it got to the offending instruction. 114 115 By turning this off, you may save a tiny amount of power. 116 117choice 118 prompt "Omit loop Tracing" 119 default DEBUG_BFIN_HWTRACE_COMPRESSION_OFF 120 depends on DEBUG_BFIN_HWTRACE_ON 121 help 122 The trace buffer can be configured to omit recording of changes in 123 program flow that match either the last entry or one of the last 124 two entries. Omitting one of these entries from the record prevents 125 the trace buffer from overflowing because of any sort of loop (for, do 126 while, etc) in the program. 127 128 Because zero-overhead Hardware loops are not recorded in the trace buffer, 129 this feature can be used to prevent trace overflow from loops that 130 are nested four deep. 131 132config DEBUG_BFIN_HWTRACE_COMPRESSION_OFF 133 bool "Trace all Loops" 134 help 135 The trace buffer records all changes of flow 136 137config DEBUG_BFIN_HWTRACE_COMPRESSION_ONE 138 bool "Compress single-level loops" 139 help 140 The trace buffer does not record single loops - helpful if trace 141 is spinning on a while or do loop. 142 143config DEBUG_BFIN_HWTRACE_COMPRESSION_TWO 144 bool "Compress two-level loops" 145 help 146 The trace buffer does not record loops two levels deep. Helpful if 147 the trace is spinning in a nested loop 148 149endchoice 150 151config DEBUG_BFIN_HWTRACE_COMPRESSION 152 int 153 depends on DEBUG_BFIN_HWTRACE_ON 154 default 0 if DEBUG_BFIN_HWTRACE_COMPRESSION_OFF 155 default 1 if DEBUG_BFIN_HWTRACE_COMPRESSION_ONE 156 default 2 if DEBUG_BFIN_HWTRACE_COMPRESSION_TWO 157 158 159config DEBUG_BFIN_HWTRACE_EXPAND 160 bool "Expand Trace Buffer greater than 16 entries" 161 depends on DEBUG_BFIN_HWTRACE_ON 162 default n 163 help 164 By selecting this option, every time the 16 hardware entries in 165 the Blackfin's HW Trace buffer are full, the kernel will move them 166 into a software buffer, for dumping when there is an issue. This 167 has a great impact on performance, (an interrupt every 16 change of 168 flows) and should normally be turned off, except in those nasty 169 debugging sessions 170 171config DEBUG_BFIN_HWTRACE_EXPAND_LEN 172 int "Size of Trace buffer (in power of 2k)" 173 range 0 4 174 depends on DEBUG_BFIN_HWTRACE_EXPAND 175 default 1 176 help 177 This sets the size of the software buffer that the trace information 178 is kept in. 179 0 for (2^0) 1k, or 256 entries, 180 1 for (2^1) 2k, or 512 entries, 181 2 for (2^2) 4k, or 1024 entries, 182 3 for (2^3) 8k, or 2048 entries, 183 4 for (2^4) 16k, or 4096 entries 184 185config DEBUG_BFIN_NO_KERN_HWTRACE 186 bool "Turn off hwtrace in CPLB handlers" 187 depends on DEBUG_BFIN_HWTRACE_ON 188 default y 189 help 190 The CPLB error handler contains a lot of flow changes which can 191 quickly fill up the hardware trace buffer. When debugging crashes, 192 the hardware trace may indicate that the problem lies in kernel 193 space when in reality an application is buggy. 194 195 Say Y here to disable hardware tracing in some known "jumpy" pieces 196 of code so that the trace buffer will extend further back. 197 198config EARLY_PRINTK 199 bool "Early printk" 200 default n 201 select SERIAL_CORE_CONSOLE 202 help 203 This option enables special console drivers which allow the kernel 204 to print messages very early in the bootup process. 205 206 This is useful for kernel debugging when your machine crashes very 207 early before the console code is initialized. After enabling this 208 feature, you must add "earlyprintk=serial,uart0,57600" to the 209 command line (bootargs). It is safe to say Y here in all cases, as 210 all of this lives in the init section and is thrown away after the 211 kernel boots completely. 212 213config NMI_WATCHDOG 214 bool "Enable NMI watchdog to help debugging lockup on SMP" 215 default n 216 depends on SMP 217 help 218 If any CPU in the system does not execute the period local timer 219 interrupt for more than 5 seconds, then the NMI handler dumps debug 220 information. This information can be used to debug the lockup. 221 222config CPLB_INFO 223 bool "Display the CPLB information" 224 help 225 Display the CPLB information via /proc/cplbinfo. 226 227config ACCESS_CHECK 228 bool "Check the user pointer address" 229 default y 230 help 231 Usually the pointer transfer from user space is checked to see if its 232 address is in the kernel space. 233 234 Say N here to disable that check to improve the performance. 235 236config BFIN_ISRAM_SELF_TEST 237 bool "isram boot self tests" 238 default n 239 help 240 Run some self tests of the isram driver code at boot. 241 242config BFIN_PSEUDODBG_INSNS 243 bool "Support pseudo debug instructions" 244 default n 245 help 246 This option allows the kernel to emulate some pseudo instructions which 247 allow simulator test cases to be run under Linux with no changes. 248 249 Most people should say N here. 250 251config BFIN_PM_WAKEUP_TIME_BENCH 252 bool "Display the total time for kernel to resume from power saving mode" 253 default n 254 help 255 Display the total time when kernel resumes normal from standby or 256 suspend to mem mode. 257 258endmenu 259