How to get past ebreak instruction on RISC-V
Simon Marchi
simon.marchi@polymtl.ca
Tue Jan 12 16:15:37 GMT 2021
On 2021-01-12 11:07 a.m., Jan Vrany wrote:
> Hi,
>
> I'm working on RISC-V compiler. To ease debugging of compiled code
> I'm inserting `ebreak` instruction to interesting place (entry/exit
> points or as a placeholder for unimplemented features).
>
> For example, the code might look like:
>
> (gdb) disas 0x0000003FD6A36024, 0x0000003FD6A36048
> Dump of assembler code from 0x3fd6a36024 to 0x3fd6a36048:
> => 0x0000003fd6a36024: ebreak
> 0x0000003fd6a36028: sd ra,-8(s11)
> 0x0000003fd6a3602c: addi s11,s11,-16
> 0x0000003fd6a36030: ld t3,80(s10)
> 0x0000003fd6a36034: addiw a0,zero,42
> 0x0000003fd6a36038: addi s11,s11,16
> 0x0000003fd6a3603c: ret
> 0x0000003fd6a36040: blt s11,t3,0x3fd6a36000
> 0x0000003fd6a36044: ebreak
> End of assembler dump.
> (gdb)
>
> When compiled function is (attempted to) run, it stops on `ebreak`
> as expected:
>
> Thread 2 "main" received signal SIGTRAP, Trace/breakpoint trap.
> [Switching to Thread 0x3ff7e681e0 (LWP 428777)]
> 0x0000003fd6a36024 in ?? ()
>
> How can I get past the `ebreak` so I can `stepi` thought the following
> instructions and debug? Thanks!
I suppose you could do "set $pc = 0x3fd6a36028". But really this is
something that GDB should be doing automatically, adjusting the PC
after hitting that style of breakpoint.
Simon
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