| Message ID | 20171103123009.18705-2-christian.storm@siemens.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [01/11] Lua: expose get_tmpdir() to Lua | expand |
On 03/11/2017 13:30, Christian Storm wrote: > Some SWUpdate-internal img_type attributes should not be > "officially" exposed to the Lua realm but they may be > required when calling, e.g., copyfile() from within a Lua > handler or when chaining handlers, i.e., calling a C handler > from within a Lua handler. > > One such example is img_type's offset attribute designating > the offset in the cpio file which is used by, e.g., copyfile(). > > "Hide" those SWUpdate-internal attributes in a metatable so > that they're not "visible" in the Lua realm, e.g., by > pairs() enumeration, but still can be transported from the > C to the Lua realm and vice versa. Although these "hidden" > attributes can be accessed directly from the Lua realm, the > access pattern, e.g., image["_private"]["offset"], strongly > hints not to mess with the image["_private"] table values > from within the Lua realm. > > Signed-off-by: Christian Storm <christian.storm@siemens.com> > --- > corelib/lua_interface.c | 29 +++++++++++++++++++++++++++++ > 1 file changed, 29 insertions(+) > > diff --git a/corelib/lua_interface.c b/corelib/lua_interface.c > index a41629f..8b8851e 100644 > --- a/corelib/lua_interface.c > +++ b/corelib/lua_interface.c > @@ -267,6 +267,26 @@ static void lua_number_to_img(struct img_type *img, const char *key, > static void image2table(lua_State* L, struct img_type *img) { > if (L && img) { > lua_newtable (L); > + > + /* > + * Create a metatable to "hide" SWUpdate-internal attributes. > + * These are not "visible", e.g., by pairs() enumeration but > + * may be accessed directly, knowing the attribute paths. > + * An example is img_type's offset designating the offset > + * in the cpio file which is used by, e.g., copyfile(). > + * While not visible in pairs() enumeration, it is directly > + * accessible by image["_private"]["offset"]. > + * This access pattern strongly hints not to mess with the > + * image["_private"] table values from within the Lua realm. > + */ > + lua_newtable(L); > + lua_pushvalue(L, -1); > + lua_pushstring(L, "_private"); > + lua_newtable(L); > + lua_settable(L, -3); > + lua_setfield(L, -2, "__index"); > + lua_setmetatable(L, -2); > + > LUA_PUSH_IMG_STRING(img, "name", id.name); > LUA_PUSH_IMG_STRING(img, "version", id.version); > LUA_PUSH_IMG_STRING(img, "filename", fname); > @@ -289,6 +309,10 @@ static void image2table(lua_State* L, struct img_type *img) { > LUA_PUSH_IMG_NUMBER(img, "size", size); > LUA_PUSH_IMG_NUMBER(img, "checksum", checksum); > > + lua_getfield(L, -1, "_private"); > + LUA_PUSH_IMG_NUMBER(img, "offset", offset); > + lua_pop(L, 1); > + > char *hashstring = alloca(2 * SHA256_HASH_LENGTH + 1); > hash_to_ascii(img->sha256, hashstring); > lua_pushstring(L, "sha256"); > @@ -315,6 +339,11 @@ static void table2image(lua_State* L, struct img_type *img) { > } > lua_pop(L, 1); > } > + > + lua_getfield(L, -1, "_private"); > + lua_getfield(L, -1, "offset"); > + img->offset = (off_t)luaL_checknumber(L, -1); > + lua_pop(L,2); > } > } > > Applied to -master, thanks ! Best regards, Stefano Babic
diff --git a/corelib/lua_interface.c b/corelib/lua_interface.c index a41629f..8b8851e 100644 --- a/corelib/lua_interface.c +++ b/corelib/lua_interface.c @@ -267,6 +267,26 @@ static void lua_number_to_img(struct img_type *img, const char *key, static void image2table(lua_State* L, struct img_type *img) { if (L && img) { lua_newtable (L); + + /* + * Create a metatable to "hide" SWUpdate-internal attributes. + * These are not "visible", e.g., by pairs() enumeration but + * may be accessed directly, knowing the attribute paths. + * An example is img_type's offset designating the offset + * in the cpio file which is used by, e.g., copyfile(). + * While not visible in pairs() enumeration, it is directly + * accessible by image["_private"]["offset"]. + * This access pattern strongly hints not to mess with the + * image["_private"] table values from within the Lua realm. + */ + lua_newtable(L); + lua_pushvalue(L, -1); + lua_pushstring(L, "_private"); + lua_newtable(L); + lua_settable(L, -3); + lua_setfield(L, -2, "__index"); + lua_setmetatable(L, -2); + LUA_PUSH_IMG_STRING(img, "name", id.name); LUA_PUSH_IMG_STRING(img, "version", id.version); LUA_PUSH_IMG_STRING(img, "filename", fname); @@ -289,6 +309,10 @@ static void image2table(lua_State* L, struct img_type *img) { LUA_PUSH_IMG_NUMBER(img, "size", size); LUA_PUSH_IMG_NUMBER(img, "checksum", checksum); + lua_getfield(L, -1, "_private"); + LUA_PUSH_IMG_NUMBER(img, "offset", offset); + lua_pop(L, 1); + char *hashstring = alloca(2 * SHA256_HASH_LENGTH + 1); hash_to_ascii(img->sha256, hashstring); lua_pushstring(L, "sha256"); @@ -315,6 +339,11 @@ static void table2image(lua_State* L, struct img_type *img) { } lua_pop(L, 1); } + + lua_getfield(L, -1, "_private"); + lua_getfield(L, -1, "offset"); + img->offset = (off_t)luaL_checknumber(L, -1); + lua_pop(L,2); } }
Some SWUpdate-internal img_type attributes should not be "officially" exposed to the Lua realm but they may be required when calling, e.g., copyfile() from within a Lua handler or when chaining handlers, i.e., calling a C handler from within a Lua handler. One such example is img_type's offset attribute designating the offset in the cpio file which is used by, e.g., copyfile(). "Hide" those SWUpdate-internal attributes in a metatable so that they're not "visible" in the Lua realm, e.g., by pairs() enumeration, but still can be transported from the C to the Lua realm and vice versa. Although these "hidden" attributes can be accessed directly from the Lua realm, the access pattern, e.g., image["_private"]["offset"], strongly hints not to mess with the image["_private"] table values from within the Lua realm. Signed-off-by: Christian Storm <christian.storm@siemens.com> --- corelib/lua_interface.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)