[Tarantool-patches] [PATCH luajit v1] tools: fix luajit-gdb stack dump

[Igor Munkin]

Sergey,

I've checked the patch into all long-term branches in tarantool/luajit
and bumped a new version in 1.10, 2.7, 2.8 and master.

On 18.06.21, Sergey Kaplun wrote:
> When there is only one frame (so-called dummy frame) with a dummy thread
> on stack bottom at L->base - 1 - LJ_FR2, stack dump does not show stack
> slots from bottom to top, because the frame link is already pointed to
> stack bottom (dummy thread mentioned above). Its output looks like the
> following:
> 
> | 0x7fb512ac40:0x7fb512ac70 [    ] 7 slots: Red zone
> | 0x7fb512ac38            [   M]
> | 0x7fb512ab28:0x7fb512ac30 [    ] 34 slots: Free stack slots
> | 0x7fb512ab20            [  T ]
> | 0x7fb512ab08:0x7fb512ab10 [S   ] FRAME: dummy L
> 
> This patch unrolled first loop iteration. Stack dump first inspect all
> fields for the top frame and then continue if there are other frames.
> After patch the output looks like the following:
> 
> | 0x7fb512ac40:0x7fb512ac70 [    ] 7 slots: Red zone
> | 0x7fb512ac38            [   M]
> | 0x7fb512ab28:0x7fb512ac30 [    ] 34 slots: Free stack slots
> | 0x7fb512ab20            [  T ]
> | 0x7fb512ab18            [    ] VALUE: string 0 "/tmp/net_box.lua:6: err in ser" @ 0x7fb512ade8
> | 0x7fb512ab10            [ B  ] VALUE: table @ 0x7fb512ac80 (asize: 0, hmask: 0x0)
> | 0x7fb512ab00:0x7fb512ab08 [S   ] FRAME: dummy L
> ---
> 
> Branch: https://github.com/tarantool/luajit/tree/skaplun/fix-luajit-gdb
> 
> Steps to test behaviour:
> 0) Clone branch
> 1) Build tarantool with GC64 or not (I've tested both cases)
> 2) Run the following script </tmp/net_box.lua> by Tarantool via gdb.
> 
> | $ cat /tmp/netbox.lua
> | box.cfg{log_level = 50, listen = "127.0.0.1:3802"}
> | box.schema.user.grant('guest','read,write,execute','universe', nil, {if_not_exists=true})
> | local net_box = require"net.box"
> | local cn = net_box:connect("127.0.0.1:3802")
> | local function f()
> |   return setmetatable({}, {__serialize = function() error[[err in ser]] end})
> | end
> | _G.f = f
> | local r, st = cn:call("f")
> | print(r,st)
> 
> | $ gdb --args ./tarantool /tmp/netbox.lua
> | ...
> | (gdb) source ~/builds_workspace/luajit/fix-luajit-gdb/src/luajit-gdb.py
> | ...
> 
> 3) Set breakpoint to ./src/lua/msgpack.c:234, and run
> 
> | (gdb) b ./src/lua/msgpack.c:234
> 
> I'm not sure about your sources version, so you can just set breakpoin to
> mp_encode(), run and continue (need two entries). We are interested in
> the line #234:
> 
> | 233|.......if (luaL_tofield(L, cfg, opts, lua_gettop(L), &field) < 0)
> | 234|.......|.......return luaT_error(L);
> 
> And dump the stack:
> 
> | (gdb) lj-stack L
> | 0x7fb512ac40:0x7fb512ac70 [    ] 7 slots: Red zone
> | 0x7fb512ac38            [   M]
> | 0x7fb512ab28:0x7fb512ac30 [    ] 34 slots: Free stack slots
> | 0x7fb512ab20            [  T ]
> | 0x7fb512ab18            [    ] VALUE: string 0 "/tmp/net_box.lua:6: err in ser" @ 0x7fb512ade8
> | 0x7fb512ab10            [ B  ] VALUE: table @ 0x7fb512ac80 (asize: 0, hmask: 0x0)
> | 0x7fb512ab00:0x7fb512ab08 [S   ] FRAME: dummy L
> 
>  src/luajit-gdb.py | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
> 

<snipped>

> -- 
> 2.31.0
> 

-- 
Best regards,
IM