Hi All,
This question is partially a development question, but since I know that most
of the prior conversations concerning the m5threads package has been on the
gem5-user/m5-user lists, I want to make sure that all folks with m5threads
experience see my question.
Does anyone have experience successfully using the OpenMP test in the m5threads
package? The particular ISA doesn't matter. If so, I would be curious to know
if you needed to make changes to pthreads.c, in particular the function
"setup_thread_tls", to make it work. Those of you familiar with that code know
that there is some nasty pointer arithmetic in that function to copy the TLS
from the ELF structure to the main thread's simulated TLS. The confusing thing
is that the pointer to the destination TLS is aligned twice. First the
tlsblock pointer is aligned according to the tls_align value, then the tlsblock
pointer is aligned to some confusing combination of the tcb_offset and memsz to
produce the tls_start_ptr. My experience using the pthread tests that the
second alignment makes no modifications and essentially copies the tlsblock
value to the tls_start_ptr. However, for the OpenMP test, the second alignment
sets the tls_start_ptr to an illegal value, thus crashing the program.
I'm not sure why the second alignment modification is even necessary, and the
OpenMP test seems to work if you simply remove it. See diff below. However,
before I check in the change, I would like to know if others have a better
understanding why the second alignment statement was added (...Daniel Sanchez?)
diff --git a/pthread.c b/pthread.c
--- a/pthread.c
+++ b/pthread.c
@@ -151,11 +151,9 @@
void* tlsblock = (void *) (((uintptr_t) th_block_addr +
thread_block_info.tls_align - 1)
& ~(thread_block_info.tls_align - 1));
/* Initialize the TLS block. */
- char* tls_start_ptr = ((char *) tlsblock + tcb_offset
- - roundup (thread_block_info.tls_memsz,
thread_block_info.tls_align ?: 1));
//DEBUG("Init TLS: Copying %d bytes from 0x%llx to 0x%llx\n", filesz,
(uint64_t) initimage, (uint64_t) tls_start_ptr)
;
- memcpy (tls_start_ptr, thread_block_info.tls_initimage,
thread_block_info.tls_filesz);
+ memcpy (tlsblock, thread_block_info.tls_initimage,
thread_block_info.tls_filesz);
//Rest of tls vars are already cleared (mmap returns zeroed memory)
Thanks,
Brad
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