Frank Ch Eigler writes: > Hi, Lluís - >> I've attached both. BTW, I'm using debian's gcc 6.1.1-1.
> Thank you. Those both look just fine, argh. Could you try using > gdb's "static probe points" facility to break at the same point, to > see if the arguments are accessible? > https://sourceware.org/gdb/onlinedocs/gdb/Static-Probe-Points.html > Maybe provide a disassembly of the two functions of that binary, just > to confirm that the numeric parameters are being passed? Everything seems correct (gdb 7.11.1-2), so either the kernel or systemtap are garbling up the arguments when retrieving them, or systemtap gets confused and gets them from the wrong place. $ gdb ./test (gdb) break main (gdb) run Starting program: /home/lluis/tmp/systemtap/test Breakpoint 3, main (argc=1, argv=0x7fffffffe168) at test.c:12 12 f(1, 1); # just in case, I made sure the program is loaded (gdb) disassemble main Dump of assembler code for function main: 0x000000000040050f <+0>: push %rbp 0x0000000000400510 <+1>: mov %rsp,%rbp 0x0000000000400513 <+4>: sub $0x10,%rsp 0x0000000000400517 <+8>: mov %edi,-0x4(%rbp) 0x000000000040051a <+11>: mov %rsi,-0x10(%rbp) => 0x000000000040051e <+15>: mov $0x1,%esi 0x0000000000400523 <+20>: mov $0x1,%edi 0x0000000000400528 <+25>: callq 0x4004e6 <f> 0x000000000040052d <+30>: mov $0x2,%esi 0x0000000000400532 <+35>: mov $0x2,%edi 0x0000000000400537 <+40>: callq 0x4004e6 <f> 0x000000000040053c <+45>: mov $0x0,%eax 0x0000000000400541 <+50>: leaveq 0x0000000000400542 <+51>: retq (gdb) disassemble f Dump of assembler code for function f: 0x00000000004004e6 <+0>: push %rbp 0x00000000004004e7 <+1>: mov %rsp,%rbp 0x00000000004004ea <+4>: sub $0x10,%rsp 0x00000000004004ee <+8>: mov %edi,-0x4(%rbp) 0x00000000004004f1 <+11>: mov %esi,-0x8(%rbp) 0x00000000004004f4 <+14>: nop 0x00000000004004f5 <+15>: mov -0x8(%rbp),%edx 0x00000000004004f8 <+18>: mov -0x4(%rbp),%eax 0x00000000004004fb <+21>: mov %eax,%esi 0x00000000004004fd <+23>: mov $0x4005d4,%edi 0x0000000000400502 <+28>: mov $0x0,%eax 0x0000000000400507 <+33>: callq 0x4003c0 <printf@plt> 0x000000000040050c <+38>: nop 0x000000000040050d <+39>: leaveq 0x000000000040050e <+40>: retq (gdb) info probes Type Provider Name Where Semaphore Object stap test f 0x00000000004004f4 0x0000000000600988 /home/lluis/tmp/systemtap/test (gdb) enable probes test Probe test:f cannot be enabled. (gdb) b -probe test:f Breakpoint 1 at 0x4004f4 (gdb) info b Num Type Disp Enb Address What 1 breakpoint keep y 0x00000000004004f4 -probe test:f (gdb) c Continuing. Breakpoint 1, f (a1=1, a2=1) at test.c:6 6 TEST_F(a1, a2); (gdb) p $rsi $1 = 1 (gdb) p $rdi $2 = 1 (gdb) c Continuing. a1=1 a2=1 Breakpoint 1, f (a1=2, a2=2) at test.c:6 6 TEST_F(a1, a2); (gdb) p $rsi $3 = 2 (gdb) p $rdi $4 = 2 (gdb) c Continuing. a1=2 a2=2 [Inferior 1 (process 30372) exited normally] Thanks, Lluis
