powerpc/kgdb: add kgdb_arch_set/remove_breakpoint()

[Michael Ellerman]

On Tue, 2018-09-18 at 09:26:03 UTC, Christophe Leroy wrote:
> Generic implementation fails to remove breakpoints after init
> when CONFIG_STRICT_KERNEL_RWX is selected:
> 
> [   13.251285] KGDB: BP remove failed: c001c338
> [   13.259587] kgdbts: ERROR PUT: end of test buffer on 'do_fork_test' line 8 expected OK got $E14#aa
> [   13.268969] KGDB: re-enter exception: ALL breakpoints killed
> [   13.275099] CPU: 0 PID: 1 Comm: init Not tainted 4.18.0-g82bbb913ffd8 #860
> [   13.282836] Call Trace:
> [   13.285313] [c60e1ba0] [c0080ef0] kgdb_handle_exception+0x6f4/0x720 (unreliable)
> [   13.292618] [c60e1c30] [c000e97c] kgdb_handle_breakpoint+0x3c/0x98
> [   13.298709] [c60e1c40] [c000af54] program_check_exception+0x104/0x700
> [   13.305083] [c60e1c60] [c000e45c] ret_from_except_full+0x0/0x4
> [   13.310845] [c60e1d20] [c02a22ac] run_simple_test+0x2b4/0x2d4
> [   13.316532] [c60e1d30] [c0081698] put_packet+0xb8/0x158
> [   13.321694] [c60e1d60] [c00820b4] gdb_serial_stub+0x230/0xc4c
> [   13.327374] [c60e1dc0] [c0080af8] kgdb_handle_exception+0x2fc/0x720
> [   13.333573] [c60e1e50] [c000e928] kgdb_singlestep+0xb4/0xcc
> [   13.339068] [c60e1e70] [c000ae1c] single_step_exception+0x90/0xac
> [   13.345100] [c60e1e80] [c000e45c] ret_from_except_full+0x0/0x4
> [   13.350865] [c60e1f40] [c000e11c] ret_from_syscall+0x0/0x38
> [   13.356346] Kernel panic - not syncing: Recursive entry to debugger
> 
> This patch creates powerpc specific version of
> kgdb_arch_set_breakpoint() and kgdb_arch_remove_breakpoint()
> using patch_instruction()
> 
> Fixes: 1e0fc9d1eb2b ("powerpc/Kconfig: Enable STRICT_KERNEL_RWX for some configs")
> Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/fb978ca207743badfe7efd9eebe68b

cheers