https://bugzilla.novell.com/show_bug.cgi?id=352419
Summary: strace shows wrong system call
Product: openSUSE 10.2
Version: Final
Platform: x86-64
OS/Version: openSUSE 10.2
Status: NEW
Severity: Normal
Priority: P5 - None
Component: Development
AssignedTo: pth@novell.com
ReportedBy: opensuse.org@contacts.eelis.net
QAContact: qa@suse.de
Found By: Customer
Consider the following small program:
#include
#include
int main ()
{
printf("--------------------\n");
__asm__("movl $2, %eax; int $0x80");
printf("[i am %d]\n", getpid());
}
When compiled and run with gcc t.c && ./a.out I get:
--------------------
[i am 10869]
[i am 10868]
This is what I would expect, as the assembly code performs a fork() (because 2
is SYS_fork on i386, and from what I understand the "int $0x80" performs an
emulated i386 system call).
However, when I run strace ./a.out I get:
execve("./a.out", ["./a.out"], [/* 81 vars */]) = 0
brk(0) = 0x602000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x2b039717c000
uname({sys="Linux", node="groen", ...}) = 0
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or
directory)
open("/etc/ld.so.cache", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=218416, ...}) = 0
mmap(NULL, 218416, PROT_READ, MAP_PRIVATE, 3, 0) = 0x2b039717d000
close(3) = 0
open("/lib64/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\340\333"..., 832) =
832
fstat(3, {st_mode=S_IFREG|0755, st_size=1595305, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x2b03971b3000
mmap(NULL, 3412216, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) =
0x2b039737e000
fadvise64(3, 0, 3412216, POSIX_FADV_WILLNEED) = 0
mprotect(0x2b03974b7000, 2093056, PROT_NONE) = 0
mmap(0x2b03976b6000, 20480, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x138000) = 0x2b03976b6000
mmap(0x2b03976bb000, 16632, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x2b03976bb000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x2b03976c0000
arch_prctl(ARCH_SET_FS, 0x2b03976c06f0) = 0
mprotect(0x2b03976b6000, 12288, PROT_READ) = 0
mprotect(0x600000, 4096, PROT_READ) = 0
munmap(0x2b039717d000, 218416) = 0
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 11), ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x2b039717d000
write(1, "--------------------\n", 21--------------------
) = 21
open(umovestr: Input/output error
0x1, O_WRONLY|0x14[i am 10873]
) = 10873
--- SIGCHLD (Child exited) @ 0 (0) ---
getpid() = 10872
write(1, "[i am 10872]\n", 13[i am 10872]
) = 13
exit_group(13) = ?
Process 10872 detached
Note how a call to open() is reported instead of a call to fork(). Also note
how fork() /is/ executed (we see both "[i am 10873]" and "[i am 10872]"). My
guess is that strace thinks it's a call to open() because 2 is SYS_open on
x86_64.
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