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This splits up the contiguous JITed dump obtained via the bpf
system call into more relatable chunks for each function in
the program. If the kernel symbols corresponding to these are
known, they are printed in the header for each JIT image dump
otherwise the masked start address is printed.
Before applying this patch:
# bpftool prog dump jited id 1
0: push %rbp
1: mov %rsp,%rbp
...
70: leaveq
71: retq
72: push %rbp
73: mov %rsp,%rbp
...
dd: leaveq
de: retq
# bpftool -p prog dump jited id 1
[{
"pc": "0x0",
"operation": "push",
"operands": ["%rbp"
]
},{
...
},{
"pc": "0x71",
"operation": "retq",
"operands": [null
]
},{
"pc": "0x72",
"operation": "push",
"operands": ["%rbp"
]
},{
...
},{
"pc": "0xde",
"operation": "retq",
"operands": [null
]
}
]
After applying this patch:
# echo 0 > /proc/sys/net/core/bpf_jit_kallsyms
# bpftool prog dump jited id 1
0xffffffffc02c7000:
0: push %rbp
1: mov %rsp,%rbp
...
70: leaveq
71: retq
0xffffffffc02cf000:
0: push %rbp
1: mov %rsp,%rbp
...
6b: leaveq
6c: retq
# bpftool -p prog dump jited id 1
[{
"name": "0xffffffffc02c7000",
"insns": [{
"pc": "0x0",
"operation": "push",
"operands": ["%rbp"
]
},{
...
},{
"pc": "0x71",
"operation": "retq",
"operands": [null
]
}
]
},{
"name": "0xffffffffc02cf000",
"insns": [{
"pc": "0x0",
"operation": "push",
"operands": ["%rbp"
]
},{
...
},{
"pc": "0x6c",
"operation": "retq",
"operands": [null
]
}
]
}
]
# echo 1 > /proc/sys/net/core/bpf_jit_kallsyms
# bpftool prog dump jited id 1
bpf_prog_b811aab41a39ad3d_foo:
0: push %rbp
1: mov %rsp,%rbp
...
70: leaveq
71: retq
bpf_prog_cf418ac8b67bebd9_F:
0: push %rbp
1: mov %rsp,%rbp
...
6b: leaveq
6c: retq
# bpftool -p prog dump jited id 1
[{
"name": "bpf_prog_b811aab41a39ad3d_foo",
"insns": [{
"pc": "0x0",
"operation": "push",
"operands": ["%rbp"
]
},{
...
},{
"pc": "0x71",
"operation": "retq",
"operands": [null
]
}
]
},{
"name": "bpf_prog_cf418ac8b67bebd9_F",
"insns": [{
"pc": "0x0",
"operation": "push",
"operands": ["%rbp"
]
},{
...
},{
"pc": "0x6c",
"operation": "retq",
"operands": [null
]
}
]
}
]
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
|
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Currently, we resolve the callee's address for a JITed function
call by using the imm field of the call instruction as an offset
from __bpf_call_base. If bpf_jit_kallsyms is enabled, we further
use this address to get the callee's kernel symbol's name.
For some architectures, such as powerpc64, the imm field is not
large enough to hold this offset. So, instead of assigning this
offset to the imm field, the verifier now assigns the subprog
id. Also, a list of kernel symbol addresses for all the JITed
functions is provided in the program info. We now use the imm
field as an index for this list to lookup a callee's symbol's
address and resolve its name.
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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