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filter: add minimal BPF JIT image disassembler

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This is a minimal stand-alone user space helper, that allows for debugging or
verification of emitted BPF JIT images. This is in particular useful for
emitted opcode debugging, since minor bugs in the JIT compiler can be fatal.
The disassembler is architecture generic and uses libopcodes and libbfd.

How to get to the disassembly, example:

  1) `echo 2 > /proc/sys/net/core/bpf_jit_enable`
  2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`)
  3) Run e.g. `bpf_jit_disasm -o` to disassemble the most recent JIT code output

`bpf_jit_disasm -o` will display the related opcodes to a particular instruction
as well. Example for x86_64:

$ ./bpf_jit_disasm
94 bytes emitted from JIT compiler (pass:3, flen:9)
ffffffffa0356000 + <x>:
   0:	push   %rbp
   1:	mov    %rsp,%rbp
   4:	sub    $0x60,%rsp
   8:	mov    %rbx,-0x8(%rbp)
   c:	mov    0x68(%rdi),%r9d
  10:	sub    0x6c(%rdi),%r9d
  14:	mov    0xe0(%rdi),%r8
  1b:	mov    $0xc,%esi
  20:	callq  0xffffffffe0d01b71
  25:	cmp    $0x86dd,%eax
  2a:	jne    0x000000000000003d
  2c:	mov    $0x14,%esi
  31:	callq  0xffffffffe0d01b8d
  36:	cmp    $0x6,%eax
[...]
  5c:	leaveq
  5d:	retq

$ ./bpf_jit_disasm -o
94 bytes emitted from JIT compiler (pass:3, flen:9)
ffffffffa0356000 + <x>:
   0:	push   %rbp
	55
   1:	mov    %rsp,%rbp
	48 89 e5
   4:	sub    $0x60,%rsp
	48 83 ec 60
   8:	mov    %rbx,-0x8(%rbp)
	48 89 5d f8
   c:	mov    0x68(%rdi),%r9d
	44 8b 4f 68
  10:	sub    0x6c(%rdi),%r9d
	44 2b 4f 6c
[...]
  5c:	leaveq
	c9
  5d:	retq
	c3

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann
2013-03-20 12:11:47 +00:00
committed by David S. Miller
parent b34870fc9f
commit e306e2c13b
3 changed files with 220 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tools/Makefile
+6 -5
View File
@@ -12,6 +12,7 @@ help:
@echo ' turbostat - Intel CPU idle stats and freq reporting tool'
@echo ' usb - USB testing tools'
@echo ' virtio - vhost test module'
@echo ' net - misc networking tools'
@echo ' vm - misc vm tools'
@echo ' x86_energy_perf_policy - Intel energy policy tool'
@echo ''
@@ -34,7 +35,7 @@ help:
cpupower: FORCE
$(call descend,power/$@)
cgroup firewire lguest perf usb virtio vm: FORCE
cgroup firewire lguest perf usb virtio vm net: FORCE
$(call descend,$@)
selftests: FORCE
@@ -46,7 +47,7 @@ turbostat x86_energy_perf_policy: FORCE
cpupower_install:
$(call descend,power/$(@:_install=),install)
cgroup_install firewire_install lguest_install perf_install usb_install virtio_install vm_install:
cgroup_install firewire_install lguest_install perf_install usb_install virtio_install vm_install net_install:
$(call descend,$(@:_install=),install)
selftests_install:
@@ -57,12 +58,12 @@ turbostat_install x86_energy_perf_policy_install:
install: cgroup_install cpupower_install firewire_install lguest_install \
perf_install selftests_install turbostat_install usb_install \
virtio_install vm_install x86_energy_perf_policy_install
virtio_install vm_install net_install x86_energy_perf_policy_install
cpupower_clean:
$(call descend,power/cpupower,clean)
cgroup_clean firewire_clean lguest_clean perf_clean usb_clean virtio_clean vm_clean:
cgroup_clean firewire_clean lguest_clean perf_clean usb_clean virtio_clean vm_clean net_clean:
$(call descend,$(@:_clean=),clean)
selftests_clean:
@@ -73,6 +74,6 @@ turbostat_clean x86_energy_perf_policy_clean:
clean: cgroup_clean cpupower_clean firewire_clean lguest_clean perf_clean \
selftests_clean turbostat_clean usb_clean virtio_clean \
vm_clean x86_energy_perf_policy_clean
vm_clean net_clean x86_energy_perf_policy_clean
.PHONY: FORCE