| # Debugging Tips |
| |
| For general debugging info see the [Fuchsia Debugging Workflow][fuchsia-debugging-doc]. |
| |
| ## Generating debug info |
| |
| There are several GN build arguments used to control the generation of debug |
| info. |
| |
| ### `symbol_level` |
| |
| `symbol_level` specifies level of debug info to generate. |
| The default is `-g3`. |
| A useful value for getting less debug info usable in backtraces is |
| `symbol_level = 1`. |
| |
| ### BOOTFS_DEBUG_MODULES |
| |
| BOOTFS\_DEBUG\_INFO\_FILES allows one to specify which modules |
| (apps,libs,tests) have their associated debug info included |
| in the boot image. |
| |
| The value is a comma-separated list of "module short names" |
| which are generally `parent_directory/module_directory`. |
| E.g., `ulib/launchpad,utest/debugger` |
| Make-style patterns (%) are allowed, e.g., `ulib/%,utest/debugger`. |
| |
| The default is empty (meaning none). |
| |
| ## Adding debug info to boot image |
| |
| By default the boot image does not contain debug info as it |
| can require a lot of extra space. Adding debug info is useful when |
| using tools like debuggers natively. Note that this does not apply |
| to cross debugging where the debugger is running on separate machine. |
| Adding debug info to the boot image is for when you are running debugging |
| tools on zircon itself. |
| |
| Example: |
| |
| ``` |
| $ gn gen build-zircon --args='BOOTFS_DEBUG_MODULES=ulib/%,utest/debugger symbol_level = 1' |
| ``` |
| |
| This example will include in the boot image debug info files for all |
| shared libraries and for the "debugger" test program. To reduce the amount |
| of debug info to just that usable in backtraces `symbol_level = 1` |
| is passed. |
| |
| ## Debugging the kernel with QEMU+GDB. |
| |
| See "Debugging the kernel with GDB" in [QEMU](/docs/development/debugging/qemu.md) for |
| documentation on debugging zircon with QEMU+GDB. |
| |
| [fuchsia-debugging-doc]: /docs/development/debugging/debugging.md |
| |
| ## Symbolizing the backtraces |
| |
| To automatically symbolize the backtraces when running zircon, pass the logs |
| through the symbolizer as follows: |
| |
| ``` |
| fx set bringup.x64 --variant asan # or bringup.arm64 |
| fx build |
| fx ffx emu start --console | ffx debug symbolize |
| ... |
| > crasher |
| ... |
| [00021.715] 01044.01212> devmgr: crash_analyzer_listener: analyzing exception type 0x108 |
| [00021.721] 01102.01116> <== fatal exception: process crasher[2853] thread initial-thread[2867] |
| [00021.721] 01102.01116> <== fatal page fault, PC at 0x38ed815cdbd7 |
| [00021.721] 01102.01116> CS: 0 RIP: 0x38ed815cdbd7 EFL: 0x246 CR2: 0 |
| [00021.721] 01102.01116> RAX: 0 RBX: 0x1 RCX: 0x1 RDX: 0x75dec26db264 |
| [00021.722] 01102.01116> RSI: 0 RDI: 0 RBP: 0x5663cdc3f90 RSP: 0x5663cdc3f80 |
| [00021.722] 01102.01116> R8: 0 R9: 0 R10: 0 R11: 0x206 |
| [00021.722] 01102.01116> R12: 0x6a3f40970d70 R13: 0x6a3f40970db0 R14: 0x16 R15: 0x7986f4ef |
| [00021.722] 01102.01116> errc: 0x6 |
| [00021.722] 01102.01116> bottom of user stack: |
| [00021.723] 01102.01116> 0x000005663cdc3f80: 40970d70 00006a3f 9af1eb38 00006fea |p..@?j..8....o..| |
| [00021.724] 01102.01116> 0x000005663cdc3f90: 3cdc3fd0 00000566 815cdba7 000038ed |.?.<f.....\..8..| |
| [00021.724] 01102.01116> 0x000005663cdc3fa0: 00000008 00000000 9af1eb38 00006fea |........8....o..| |
| [00021.724] 01102.01116> 0x000005663cdc3fb0: 40970f70 00006a3f 40970f70 00006a3f |p..@?j..p..@?j..| |
| [00021.724] 01102.01116> 0x000005663cdc3fc0: c26db570 000075de 40970db0 00006a3f |p.m..u.....@?j..| |
| [00021.724] 01102.01116> 0x000005663cdc3fd0: 3cdc3ff0 00000566 c261cdef 000075de |.?.<f.....a..u..| |
| [00021.724] 01102.01116> 0x000005663cdc3fe0: 00000054 00000000 40970f70 00006a3f |T.......p..@?j..| |
| [00021.724] 01102.01116> 0x000005663cdc3ff0: 40970fe0 00006a3f 00000000 00000000 |...@?j..........| |
| [00021.724] 01102.01116> arch: x86_64 |
| [00021.728] 01102.01116> dso: id=31c12edecfd596b0be787e782f896efadf23e3da base=0x75dec2603000 name=libc.so |
| [00021.728] 01102.01116> dso: id=b4f9333e0d1bb7e79370905f90299d1da94e4271 base=0x51d5c67da000 name=<vDSO> |
| [00021.728] 01102.01116> dso: id=a0106c6ceae6a63d35eb7e8923ebc1a62a8df3e8 base=0x38ed815cd000 name=app:crasher |
| [00021.728] 01102.01116> dso: id=881704361e6af74805ab9e2a236ccf2962cdecc9 base=0x2ce98f7b2000 name=libfdio.so |
| [00021.738] 01102.01116> bt#01: pc 0x38ed815cdbd7 sp 0x5663cdc3f80 (app:crasher,0xbd7) |
| [00021.746] 01102.01116> bt#02: pc 0x38ed815cdba7 sp 0x5663cdc3fa0 (app:crasher,0xba7) |
| [00021.747] 01102.01116> bt#03: pc 0x75dec261cdef sp 0x5663cdc3fe0 (libc.so,0x19def) |
| [00021.749] 01102.01116> bt#04: pc 0 sp 0x5663cdc4000 |
| [00021.749] 01102.01116> bt#05: end |
| |
| start of symbolized stack: |
| #01: blind_write at ./system/uapp/crasher/crasher.c:21 |
| #02: main at ./system/uapp/crasher/crasher.c:137 |
| #03: start_main at ./third_party/ulib/musl/src/env/__libc_start_main.c:49 |
| #04: unknown, can't find pc, sp or app/library in line |
| end of symbolized stack |
| ``` |
| |
| ## Kernel commands |
| Zircon has a number of shell commands related to the kernel and debugging accessible via the `k` |
| command. More information on them can be found through `k help`. |