CODEWITHSUNDEEP
cdebugginggdb
cq674350529
cq674350529

Reputation: 118

gdb can't insert a breakpoint when attach to a process

I'm trying to attach gdb to a program started by socat like this:

socat TCP-LISTEN:5678,reuseaddr,fork EXEC:./test

In another terminal,

sudo gdb 
attach `pidof socat`
br *0x080487D4

when execute continue command in gdb, it shows error like this:

Warning:
Cannot insert breakpoint 1.
Cannot access memory at address 0x80487d4

Command aborted.

0x080487D4 is in .text of test program. The follow-fork-mode of gdb is child, I have searched online but still can't solve it.

I debugged program successfully like this way a month ago, and don't know why it doesn't work now. But it's ok if debug the program directly using gdb like this:

gdb -q ./test

However, the way above doesn't meet my needs.

Through debugging, I think gdb expects that address is a valid address in the socat rather then test program. So how can I set breakpoints in test program? Without breakpoints in test program, it will run directly to the end when execute continue command. Setting breakpoints in socat program is useless.

Any advice? Thanks in advance.

Upvotes: 4

Views: 2795

Answers (1)

cq674350529
cq674350529

Reputation: 118

I have figured out how to set breakpoints in test program.

When start test program using socat, it won't fork a test process until a socket connection comes. So trying to set breakpoints directly in test program fails.

I use a tool(for my purpose, choose pwntools) to connect to it and suspend it ,then use gdb to attach to the forked test process. Next, I can debug normally.

Any better ideas? Thanks in advance.

Upvotes: 2

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