opnd_compute_address() does not use app segment values

[derekbruening]

From [email protected] on August 04, 2011 14:10:33

after issue #495 was fixed I tried Dr. Memory with the linux private loader but there's another problem in the way:

new thread #0 id=26199
in event_thread_init()
fs base=0x19e25000, gs base=0x19e29940

TAG 0xf77940db
+0 L3 65 8b 0d 0c 00 00 00 mov %gs:0x0c -> %ecx
+7 L3 85 c9 test %ecx %ecx
+9 L3 0f 85 f1 00 00 00 jnz $0xf77941db
END 0xf77940db

whole-bb scratch: r1 =%edx spill#0 x0, r2 =%eax spill#1 x0
fastpath: mov %gs:0x0c -> %ecx | prop=1 srcsz=4 dstsz=4 checkdef=0 markdef=0 checkunaddr=0
fastpath: test %ecx %ecx | prop=2 srcsz=4 dstsz=4 checkdef=1 markdef=0 checkunaddr=0
whole-bb scratch: r1 =used, r2 =used, efl=unused

slow_path 0xf77940db: mov %gs:0x0c -> %ecx
memref: read @0xf77940db 0x19e2994c 0x4 bytes (pre-dword 0x55 0x55) (was special)
WARNING: unknown region 0x19e29000-0x19e2a000: marking as defined
FATAL ERROR: ASSERT FAILURE (thread 26199): /home/bruening/drmemory/git/src/drmemory/alloc_drmem.c:1937: !dr_memory_is_dr_internal(addr) && !dr_memory_is_in_client(addr) (app is using tool's memory: please report this!)

(gdb) p /x * heapmgt
$2 = {vmheap = {start_addr = 0x19dd4000, end_addr = 0x21dd4000, alloc_start = 0x0, alloc_size = 0x8000000, num_blocks = 0x2000,

Dr. Memory computes the segment bases at startup via:
byte *gs_base =
opnd_compute_address(opnd_create_far_base_disp(SEG_GS, REG_NULL, REG_NULL,
0, 0, OPSZ_lea), &mc);

a related question is do we need this to do anything for linux:
/* Restore app's PEB and TEB fields (issue #248) */
dr_switch_to_app_state(drcontext);
conclusion is we don't need it for linux though since there is no swapping:
the private stuff is all separate and is all in DR memory (uses heap_mmap)

dr_insert_get_seg_base() is doing the right thing

so it looks like it's just opnd_compute_address()

Original issue: http://code.google.com/p/dynamorio/issues/detail?id=527

[derekbruening]

From [email protected] on August 14, 2011 08:27:10

Status: Fixed