On 15-02-25 08:50, Paul Floyd via oi-dev wrote:
I'll be asking more questions as I try to clean up more of the
outstanding issues.
My first question isn't a Valgrind question, it's a testcase that's
problematic.
The source file is here
https://sourceware.org/git/?p=valgrind.git;a=blob;f=none/tests/faultstatus.c;h=9e262395bc9c26a47dcae3c4bf91ae6c503c6c6e;hb=HEAD
(it has a few dependencies on Valgrind headers).
The testcase deliberately triggers 4 signals from errors (3
SIGBUS/SIGSEGV and one SIGFPE). On OI the 3rd one, a SIGBUS, doesn't
generate an error.
Running the testcase outside of Valgrind gives
paulf@openindiana:~/valgrind/none/tests$ ./faultstatus
Test 1: PASS
Test 2: PASS
Test 3: FAIL: no fault, or handler returned
Test 4: PASS
As a rule if the test fails outside of Valgrind it also usually fails
running under Valgrind.
The code is
// __pagesize obtained with (unsigned int)sysconf(_SC_PAGE_SIZE);
#define FILESIZE (4*__pagesize)
#define MAPSIZE (2*FILESIZE)
// in main
/* we need O_RDWR for the truncate below */
fd = open("faultstatus.tmp", O_CREAT|O_TRUNC|O_EXCL|O_RDWR, 0600);
if (fd == -1) {
perror("tmpfile");
exit(1);
}
unlink("faultstatus.tmp");
ftruncate(fd, FILESIZE);
mapping = mmap(0, MAPSIZE, PROT_READ, MAP_PRIVATE, fd, 0);
close(fd);
static void test3()
{
mapping[FILESIZE+10];
}
On my system the asm for that is
0000000000401a8e <test3>:
401a8e: 55 push %rbp
401a8f: 48 89 e5 mov %rsp,%rbp
401a92: 48 8b 05 af 0c 01 00 mov 0x10caf(%rip),%rax
# 412748 <mapping>
401a99: 8b 15 a1 0c 01 00 mov 0x10ca1(%rip),%edx
# 412740 <__pagesize>
401a9f: c1 e2 02 shl $0x2,%edx
401aa2: 83 c2 0a add $0xa,%edx
401aa5: 89 d2 mov %edx,%edx
401aa7: 48 01 d0 add %rdx,%rax
401aaa: 0f b6 00 movzbl (%rax),%eax
401aad: 90 nop
401aae: 5d pop %rbp
401aaf: c3
I'm expecting an error from the "movzbl (%rax),%eax".
Running the testcase in gdb and using pmap I see that the mmap adds a
mapping here
00007FFFAF479000 16K rw--- /lib/amd64/libc.so.1
00007FFFAF4F0000 16K r---- dev:304,65542 ino:53206 <= mmap here
00007FFFAF4FF000 4K rwxs- [ anon
There's 64k of space between the new mmap and the 4k anon mapping. That
means the 16k mmap is followed by a 48k space of unmapped memory.
Any ideas why OI doesn't generate a signal because of this read?
A+
Paul
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