drreg does not support use during DR init due to TLS not being set up
Both drreg and drmgr rely on TLS, but it's not set up during DR init:
Program received signal SIGSEGV, Segmentation fault.
(gdb) bt
#0 0x7396d994 in drmgr_current_bb_phase (drcontext=0xe774a780) at /work/drmemory/git/src/dynamorio/ext/drmgr/drmgr.c:1104
#1 0x7397aabb in drreg_reserve_aflags (drcontext=0xe774a780, ilist=0xe779512c, where=0x0)
at /work/drmemory/git/src/dynamorio/ext/drreg/drreg.c:1305
#2 0x7382be8f in reserve_aflags (drcontext=0xe774a780, ilist=0xe779512c, where=0x0) at /work/drmemory/git/src/drmemory/spill.c:441
#3 0x739515d8 in add_shadow_table_lookup (drcontext=0xe774a780, bb=0xe779512c, inst=0x0, mi=0xffdc1688, get_value=0 '\000',
value_in_reg2=0 '\000', need_offs=0 '\000', zero_rest_of_offs=0 '\000', reg1=19, reg2=20, reg3=0, check_alignment=1 '\001')
at /work/drmemory/git/src/drmemory/fastpath_x86.c:1995
#4 0x7393dc41 in generate_shared_esp_fastpath_helper (drcontext=0xe774a780, bb=0xe779512c, sp_action=SP_ADJUST_ACTION_SHADOW,
type=ESP_ADJUST_ABSOLUTE) at /work/drmemory/git/src/drmemory/stack_x86.c:752
#5 0x73840977 in generate_shared_esp_fastpath (drcontext=0xe774a780, ilist=0xe779512c, pc=0xe77fa179 '\253' <repeats 200 times>...)
at /work/drmemory/git/src/drmemory/stack.c:473
#6 0x73834aff in gencode_init () at /work/drmemory/git/src/drmemory/slowpath.c:1353
#7 0x73820d74 in instrument_init () at /work/drmemory/git/src/drmemory/instru.c:261
#8 0x7381f824 in dr_init (id=0) at /work/drmemory/git/src/drmemory/drmemory.c:2028
#9 0x567c0e3c in instrument_init () at /work/drmemory/git/src/dynamorio/core/lib/instrument.c:683Generating code at init time is not uncommon and it would be nice to support using drreg then.
Possible solutions:
- Have drreg special-case this with a static TLS data structure
- Disallow use during DR init and require clients to have a do-once in thread init to generate code
Unfortunately there does not seem to be a great solution. DR can't call the thread init event before the process init event.