[PING][PATCH] [gdb/tdep] Use cached breakpoint kind in breakpoint_kind

[Tom de Vries <tdevries@suse.de>]

On 6/7/24 16:38, Tom de Vries wrote:
> With test-case gdb.base/solib-probes-nosharedlibrary.exp on arm-linux, I get:
> ...
> (gdb) continue^M
> Continuing.^M
> ^M
> Program received signal SIGILL, Illegal instruction.^M
> 0xf7fd267a in ?? ()^M
> (gdb) FAIL: $exp: continue to breakpoint: main
> ...
> 
> This happens as follows:
> - the starti command is called,
> - gdb loads symbols for ld.so,
> - the "shlib events" breakpoint is inserted at the address of _dl_debug_state,
> - execution stops at ld.so _start, and the inserted breakpoint is removed,
> - the nosharedlibrary command is called,
> - gdb forgets about all shared library symbols,
> - the continue command is called,
> - gdb re-inserts the "shlib events" breakpoint, but the call to
>    breakpoint_kind returns the wrong value: ARM_BP_KIND_ARM instead of
>    ARM_BP_KIND_THUMB, so the wrong type of breakpoint is inserted, and
> - when execution hits the breakpoint, the SIGILL triggers.
> 
> In order to correctly set a breakpoint on an address for arm, gdb needs to
> known whether that address is in thumb or arm code, and the problem is that
> that information is no longer available due to the nosharedlibrary command.
> 
> However, the breakpoint kind is is available from the previous time the
> breakpoint was inserted.
> 
> Fix this in breakpoint_kind, by using the info cached in bl->target_info.kind,
> if available.
> 

Ping.

Thanks,
- Tom

> Tested on arm-linux.
> 
> PR tdep/31817
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31817
> ---
>   gdb/breakpoint.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
> index a973518ac5f..0c99ccc9568 100644
> --- a/gdb/breakpoint.c
> +++ b/gdb/breakpoint.c
> @@ -2792,7 +2792,11 @@ breakpoint_kind (const struct bp_location *bl, CORE_ADDR *addr)
>   							 regcache, addr);
>       }
>     else
> -    return gdbarch_breakpoint_kind_from_pc (bl->gdbarch, addr);
> +    {
> +      if (bl->target_info.kind != 0)
> +	return bl->target_info.kind;
> +      return gdbarch_breakpoint_kind_from_pc (bl->gdbarch, addr);
> +    }
>   }
>   
>   /* Rethrow the currently handled exception, if it's a TARGET_CLOSE_ERROR.
> 
> base-commit: 3a659c2a30f40c2a734fda5566098804b5ee38fc