Commits on Jan 29, 2023

1. tools/ttysnoop: Fix uninitialized 'buf' error …

   ENV: LLVM 13.0.1, Kernel 5.15.67, aarch64
   
   Overview of the error:
   
   The verifier is unhappy, if '(r10 -32)' is not initialized, see also [0].
   
     $ sudo ./ttysnoop.py 10
     bpf: Failed to load program: Permission denied
     3: (7b) *(u64 *)(r10 -8) = r6
     4: (7b) *(u64 *)(r10 -16) = r6
     5: (7b) *(u64 *)(r10 -24) = r6
     6: (bf) r1 = r10
     ...
     91: (67) r0 <<= 32
     92: (77) r0 >>= 32
     ; if (bpf_probe_read_user(&data->buf, BUFSIZE, (void *)buf))
     93: (55) if r0 != 0x0 goto pc+356
     R0_w=inv0 R6=invP0 R7=map_value(id=0,off=0,ks=4,vs=260,imm=0) R8=map_value(
       id=0,off=4,ks=4,vs=260,imm=0) R9=inv256 R10=fp0 fp-8=mmmmmmmm
       fp-16=mmmmmmmm fp-24=mmmmmmmm
     94: (79) r2 = *(u64 *)(r10 -32)
     invalid read from stack R10 off=-32 size=8
     processed 593 insns (limit 1000000) max_states_per_insn 1 total_states 48
       peak_states 48 mark_read 3
   
   This issue can also be resolved by upgrading LLVM>=14  and recompile and install
   bcc.
   
   [0] iovisor#2623
   
   Signed-off-by: Rong Tao <[email protected]>

   

   Rtoax committed Jan 29, 2023
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