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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Building PVH mini-os with libc support
Hello Andrew,
Thanks. Yup, you were right. I did an objdump of the kernel and found the offending instruction 0x5cfcb to be callq *%r15 in the console_print function (see below):
0000000000056ee9 <console_print>: 56ee9: 55 push %rbp 56eea: 48 89 e5 mov %rsp,%rbp 56eed: 41 57 push %r15 56eef: 41 56 push %r14 56ef1: 41 55 push %r13 56ef3: 41 54 push %r12 56ef5: 53 push %rbx 56ef6: 48 83 ec 18 sub $0x18,%rsp 56efa: 49 89 fe mov %rdi,%r14 56efd: 41 89 d4 mov %edx,%r12d 56f00: 48 89 65 c0 mov %rsp,-0x40(%rbp) 56f04: 8d 42 01 lea 0x1(%rdx),%eax 56f07: 48 98 cltq 56f09: 48 83 c0 0f add $0xf,%rax 56f0d: 48 83 e0 f0 and $0xfffffffffffffff0,%rax 56f11: 48 29 c4 sub %rax,%rsp 56f14: 48 89 e3 mov %rsp,%rbx 56f17: 83 3d 00 00 00 00 00 cmpl $0x0,0x0(%rip) # 56f1e <console_print+0x35> 56f1e: 74 09 je 56f29 <console_print+0x40> 56f20: 4c 8b 3d 00 00 00 00 mov 0x0(%rip),%r15 # 56f27 <console_print+0x3e> 56f27: eb 07 jmp 56f30 <console_print+0x47> 56f29: 4c 8b 3d 00 00 00 00 mov 0x0(%rip),%r15 # 56f30 <console_print+0x47> 56f30: 4d 85 f6 test %r14,%r14 56f33: 74 19 je 56f4e <console_print+0x65> 56f35: 41 80 7e 30 00 cmpb $0x0,0x30(%r14) 56f3a: 74 12 je 56f4e <console_print+0x65> 56f3c: 44 89 e2 mov %r12d,%edx 56f3f: 4c 89 f7 mov %r14,%rdi 56f42: 41 ff d7 callq *%r15 56f45: 48 8b 65 c0 mov -0x40(%rbp),%rsp 56f49: e9 84 00 00 00 jmpq 56fd2 <console_print+0xe9> 56f4e: 4d 63 ec movslq %r12d,%r13 56f51: 4c 89 ea mov %r13,%rdx 56f54: 48 89 df mov %rbx,%rdi 56f57: e8 00 00 00 00 callq 56f5c <console_print+0x73> 56f5c: 4a 8d 44 2b ff lea -0x1(%rbx,%r13,1),%rax 56f61: 48 39 c3 cmp %rax,%rbx 56f64: 73 4b jae 56fb1 <console_print+0xc8> 56f66: 48 89 de mov %rbx,%rsi 56f69: 80 3b 0a cmpb $0xa,(%rbx) 56f6c: 75 30 jne 56f9e <console_print+0xb5> 56f6e: c6 03 0d movb $0xd,(%rbx) 56f71: 0f b6 43 01 movzbl 0x1(%rbx),%eax 56f75: 88 45 cf mov %al,-0x31(%rbp) 56f78: c6 43 01 0a movb $0xa,0x1(%rbx) 56f7c: 49 89 dd mov %rbx,%r13 56f7f: 49 29 f5 sub %rsi,%r13 56f82: 41 8d 55 02 lea 0x2(%r13),%edx 56f86: 4c 89 f7 mov %r14,%rdi 56f89: 41 ff d7 callq *%r15 56f8c: 0f b6 45 cf movzbl -0x31(%rbp),%eax 56f90: 88 43 01 mov %al,0x1(%rbx) 56f93: 48 8d 73 01 lea 0x1(%rbx),%rsi 56f97: 41 83 c5 01 add $0x1,%r13d 56f9b: 45 29 ec sub %r13d,%r12d 56f9e: 48 83 c3 01 add $0x1,%rbx 56fa2: 4d 63 ec movslq %r12d,%r13 56fa5: 4a 8d 44 2e ff lea -0x1(%rsi,%r13,1),%rax 56faa: 48 39 d8 cmp %rbx,%rax 56fad: 77 ba ja 56f69 <console_print+0x80> 56faf: eb 03 jmp 56fb4 <console_print+0xcb> 56fb1: 48 89 de mov %rbx,%rsi 56fb4: 80 38 0a cmpb $0xa,(%rax) 56fb7: 75 0c jne 56fc5 <console_print+0xdc> 56fb9: c6 00 0d movb $0xd,(%rax) 56fbc: 42 c6 04 2e 0a movb $0xa,(%rsi,%r13,1) 56fc1: 41 83 c4 01 add $0x1,%r12d 56fc5: 44 89 e2 mov %r12d,%edx 56fc8: 4c 89 f7 mov %r14,%rdi 56fcb: 41 ff d7 callq *%r15 56fce: 48 8b 65 c0 mov -0x40(%rbp),%rsp 56fd2: 48 8d 65 d8 lea -0x28(%rbp),%rsp 56fd6: 5b pop %rbx 56fd7: 41 5c pop %r12 56fd9: 41 5d pop %r13 56fdb: 41 5e pop %r14 56fdd: 41 5f pop %r15 56fdf: 5d pop %rbp 56fe0: c3 retq
I added the options –fno-pic to TARGET_CFLAGS and TARGET_CPPFLAGS and –no-pie to TARGET_LDFLAGS and recompile the kernel. Now, the kernel carshed at instruction 0x673bb in the run_idle_thread function:
00000000000673ac <run_idle_thread>: 673ac: 55 push %rbp 673ad: 48 89 e5 mov %rsp,%rbp 673b0: 48 8b 05 00 00 00 00 mov 0x0(%rip),%rax # 673b7 <run_idle_thread+0xb> 673b7: 48 8b 60 10 mov 0x10(%rax),%rsp 673bb: ff 70 18 pushq 0x18(%rax) 673be: c3 retq 673bf: 5d pop %rbp 673c0: c3 retq
Finally, just to try I commented out the run_idle_thread function and the kernel crashed at the very beginning at 0x63. The kern dump in this case points to the stack:
5e: e8 00 00 00 00 callq 63 <stack_start>
0000000000000063 <stack_start>: ... 6b: 90 nop 6c: 90 nop 6d: 90 nop
I am not familiar with the XTF relocalability code. Any pointer or suggestion at this point would be again appreciated.
Thanks, Bruno On Thu, Dec 28, 2017 at 7:18 PM, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
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