cgo: include symbol version information #1397
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Here's a better ib.go that doesn't use C.strncmp. Same problem though. Attachments:
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Owner changed to r...@golang.org. Status changed to NeedsAttention. |
And the diff... can't really see anything significant. Attachments:
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You're right that not much changed! I was assuming that the call was returning the right value. I guess the next step is to verify that assumption. Can you make a wrapper my_ibv_get_device_list that calls ibv_get_device_list, prints the result using %p, and returns it? And then print the same result from Go (using %p) and see if they match? If they match, then it has to be a data structure issue. If they don't match, then it's a cgo calling issue. Status changed to WaitingForReply. |
Okay, I added a little wrapper:
/*
#include <stdio.h>
#include <infiniband/verbs.h>
struct ibv_device **my_ibv_get_device_list(int *num_devices) {
struct ibv_device** devs = ibv_get_device_list(num_devices);
printf("devs=%p\n", devs);
printf("devs[0]->node_type=%d\n", devs[0]->node_type);
return devs;
}
*/
It prints:
devs=0x2223040
devs[0]->node_type=1
deviceList=0x2223040
so the pointer makes it through fine and the struct is intact.
But with the new cgo:
devs=0x8e70f8
devs[0]->node_type=9303872
deviceList=0x8e70f8
So the pointers are fine, but the struct is already corrupted before Go gets it.
As a last resort, I ran valgrind 3.5.0 on the binary. It almost works! Things run for a
while and then something segfaults. There's some interesting warnings that might warrant
your attention. Output attached.
Attachments:
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I found the problem. The libibverbs shared library contains two versions of ibv_get_device_list: ibv_get_device_list@IBVERBS_1.0 and ibv_get_device_list@@IBVERBS_1.1. Because the files generated by 6l do not include library version information, the dynamic linker gives us the oldest one. But in fact we want the newer one. Using the old cgo model, 6l output never referred to system .so files directly (only indirectly via the stub .so files, which had proper version information). The fix will be to include the version information. It shouldn't be too hard. Status changed to Accepted. |
Hello
gopack prints:
fwrite libc.so.6 GLIBC_2.2.5
stderr libc.so.6 GLIBC_2.2.5
pthread_attr_init libpthread.so.0 GLIBC_2.2.5
pthread_attr_getstacksize libpthread.so.0 GLIBC_2.2.5
pthread_create libpthread.so.0 GLIBC_2.2.5
free libc.so.6 GLIBC_2.2.5
malloc libc.so.6 GLIBC_2.2.5
abort libc.so.6 GLIBC_2.2.5
__errno_location libc.so.6 GLIBC_2.2.5
ibv_get_device_list libibverbs.so.1 IBVERBS_1.1
strncmp libc.so.6 GLIBC_2.2.5
x1
which has the line:
ibv_get_device_list libibverbs.so.1 IBVERBS_1.1
which looks good.
But when I run my test case I attached here, I still get:
device=&{ops:{alloc_context:<nil> free_context:<nil>} node_type:59442928
transport_type:0 ...}
which still looks like the wrong function is being called.
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This issue was closed by revision 09092a7. Status changed to Fixed. |
This issue was closed.
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What steps will reproduce the problem? Reproducing the problem is a bit tricky, since you need to call a function on the ibverbs C library that is only going to return the right stuff if you have an InfiniBand controller in your machine. I tried to make my own little shared library with a simplified version of the function and the same structs as what produces the error, but it didn't reproduce the problem. If there's anything I can check with gdb that could help, let me know. I have the ibverbs debuginfo, so I can set breakpoints in it and in my Go code. So here goes... What is the expected output? With release.2010-12-08 (the old cgo), I get the following structs returned from the C function: struct ibv_device **ibv_get_device_list(int *num_devices) The values: deviceList=0x17fd3c0 &device=0x17f5740 device=&{ops:{alloc_context:0x7f8ef46d7480 free_context:0x7f8ef46d72b0} node_type:1 transport_type:0 name:[109 108 120 52 95 48 0 ...] dev_name:[117 118 101 114 98 115 48 0 ...] dev_path:[47 115 121 115 47 99 108 97 115 115 47 105 110 102 105 110 105 98 97 110 100 95 118 101 114 98 115 47 117 118 101 114 98 115 48 0 ...] ibdev_path:[47 115 121 115 47 99 108 97 115 115 47 105 110 102 105 110 105 98 97 110 100 47 109 108 120 52 95 48 0 ...]} What do you see instead? deviceList=0x1b40048 &device=0x1b40710 device=&{ops:{alloc_context:<nil> free_context:<nil>} node_type:28575552 transport_type:0 name:[garbage0] dev_name:[garbage] dev_path:[garbage] ibdev_path:[garbage]} Basically the whole struct is corrupted. Which compiler are you using (5g, 6g, 8g, gccgo)? 6g Which operating system are you using? linux Which revision are you using? (hg identify) tip release.2010-12-08 with the old cgo works fine. Please provide any additional information below. The C function looks like this: struct ibv_device **ibv_get_device_list(int *num_devices) And the structs involved: enum { IBV_SYSFS_NAME_MAX = 64, IBV_SYSFS_PATH_MAX = 256 }; struct ibv_device_ops { void *p1; // actually a function pointer void *p2; // actually a function pointer }; enum ibv_node_type { IBV_NODE_UNKNOWN = -1, IBV_NODE_CA = 1, IBV_NODE_SWITCH, IBV_NODE_ROUTER, IBV_NODE_RNIC }; enum ibv_transport_type { IBV_TRANSPORT_UNKNOWN = -1, IBV_TRANSPORT_IB = 0, IBV_TRANSPORT_IWARP }; struct ibv_device { struct ibv_device_ops ops; enum ibv_node_type node_type; enum ibv_transport_type transport_type; char name[IBV_SYSFS_NAME_MAX]; char dev_name[IBV_SYSFS_NAME_MAX]; char dev_path[IBV_SYSFS_PATH_MAX]; char ibdev_path[IBV_SYSFS_PATH_MAX]; };Attachments:
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