From: Sergey Bronnikov via Tarantool-patches <tarantool-patches@dev.tarantool.org> To: tarantool-patches@dev.tarantool.org, Sergey Kaplun <skaplun@tarantool.org>, Maxim Kokryashkin <m.kokryashkin@tarantool.org> Subject: [Tarantool-patches] [PATCH luajit v2 1/1] Fix saved bytecode encapsulated in ELF objects. Date: Tue, 30 May 2023 11:09:34 +0300 [thread overview] Message-ID: <7be88fa24695ad2f3c15a9a23bd884ca0acc36f5.1685433737.git.sergeyb@tarantool.org> (raw) From: Sergey Bronnikov <sergeyb@tarantool.org> Thanks to Dimitry Andric. (cherry picked from commit 7dbf0b05f1228c1c719866db5e5f3d58f87f74c8) Function `bcsave.lua:bcsave_elfobj()` produced an object file in ELF format with a wrong size size of `.strtab`. Wrong .strtab size causes lld to show an error message: ``` $ luajit -b -n "module_name" -e "print()" xxx.obj $ ld.lld xxx.obj ld.lld: error: xxx.obj: SHT_STRTAB string table section [index 3] is non-null terminated ``` Sergey Bronnikov: * added the description and the test for the problem Signed-off-by: Sergey Bronnikov <sergeyb@tarantool.org> Reviewed-by: Sergey Kaplun <skaplun@tarantool.org> Reviewed-by: Maxim Kokryashkin <m.kokryashkin@tarantool.org> --- Changes in v2: - Fixed comments as per review by Sergey. Branch: https://github.com/tarantool/luajit/tree/ligurio/gh-366-strtab-section-correct-size Tarantool CI: https://github.com/ligurio/tarantool/tree/ligurio/gh-xxxx-strtab-section-correct-size src/jit/bcsave.lua | 2 +- .../lj-366-strtab-correct-size.test.lua | 202 ++++++++++++++++++ 2 files changed, 203 insertions(+), 1 deletion(-) create mode 100644 test/tarantool-tests/lj-366-strtab-correct-size.test.lua diff --git a/src/jit/bcsave.lua b/src/jit/bcsave.lua index c17c88e0..2553d97e 100644 --- a/src/jit/bcsave.lua +++ b/src/jit/bcsave.lua @@ -275,7 +275,7 @@ typedef struct { o.sect[2].size = fofs(ofs) o.sect[3].type = f32(3) -- .strtab o.sect[3].ofs = fofs(sofs + ofs) - o.sect[3].size = fofs(#symname+1) + o.sect[3].size = fofs(#symname+2) ffi.copy(o.space+ofs+1, symname) ofs = ofs + #symname + 2 o.sect[4].type = f32(1) -- .rodata diff --git a/test/tarantool-tests/lj-366-strtab-correct-size.test.lua b/test/tarantool-tests/lj-366-strtab-correct-size.test.lua new file mode 100644 index 00000000..5dec6751 --- /dev/null +++ b/test/tarantool-tests/lj-366-strtab-correct-size.test.lua @@ -0,0 +1,202 @@ +local tap = require('tap') +local test = tap.test('lj-366-strtab-correct-size'):skipcond({ + -- The test is ELF-specific, and because LuaJIT exports object + -- files in ELF format for all operating systems except macOS + -- and Windows we skip test on these OSes. + -- See src/jit/bcsave.lua:bcsave_obj. + ['Disabled on Windows'] = jit.os == 'Windows', + ['Disabled on macOS'] = jit.os == 'OSX', +}) + +local ffi = require 'ffi' + +-- Command below exports bytecode as an object file in ELF format: +-- $ luajit -b -n 'lango_team' -e 'print()' xxx.obj +-- $ file xxx.obj +-- xxx.obj: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped +-- +-- With read_elf(1) it is possible displaying the entries in symbol table +-- section of the file, if it has one. Object file contains a single symbol +-- with name 'luaJIT_BC_lango_team': +-- +-- $ readelf --symbols xxx.obj +-- +-- Symbol table '.symtab' contains 2 entries: +-- Num: Value Size Type Bind Vis Ndx Name +-- 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND +-- 1: 0000000000000000 66 OBJECT GLOBAL DEFAULT 4 luaJIT_BC_lango_team +-- +-- and displaying the information contained in the file's section headers, if +-- it has any. For our purposes we are interesting in section .symtab, +-- so other sections snipped in the output: +-- +-- $ readelf --section-headers xxx.obj +-- There are 6 section headers, starting at offset 0x40: +-- +-- Section Headers: +-- [Nr] Name Type Address Offset +-- Size EntSize Flags Link Info Align +-- ... +-- +-- [ 3] .strtab STRTAB 0000000000000000 00000223 +-- 0000000000000016 0000000000000000 0 0 1 +-- ... +-- Reference numbers for strtab offset and size could be obtained with +-- readelf(1). Note that number system of these numbers are hexadecimal. + +local expected_strtab_size = 0x16 +local expected_strtab_offset = 0x223 +local module_name = 'lango_team' + +-- Symbol name prefix for LuaJIT bytecode defined in bcsave.lua. +local LJBC_PREFIX = 'luaJIT_BC_' + +-- Defined in elf.h. +local SHT_SYMTAB = 2 + +-- Using the same declarations as defined in <src/jit/bcsave.lua>. +ffi.cdef[[ +typedef struct { + uint8_t emagic[4], eclass, eendian, eversion, eosabi, eabiversion, epad[7]; + uint16_t type, machine; + uint32_t version; + uint32_t entry, phofs, shofs; + uint32_t flags; + uint16_t ehsize, phentsize, phnum, shentsize, shnum, shstridx; +} ELF32header; + +typedef struct { + uint8_t emagic[4], eclass, eendian, eversion, eosabi, eabiversion, epad[7]; + uint16_t type, machine; + uint32_t version; + uint64_t entry, phofs, shofs; + uint32_t flags; + uint16_t ehsize, phentsize, phnum, shentsize, shnum, shstridx; +} ELF64header; + +typedef struct { + uint32_t name, type, flags, addr, ofs, size, link, info, align, entsize; +} ELF32sectheader; + +typedef struct { + uint32_t name, type; + uint64_t flags, addr, ofs, size; + uint32_t link, info; + uint64_t align, entsize; +} ELF64sectheader; + +typedef struct { + uint32_t name, value, size; + uint8_t info, other; + uint16_t sectidx; +} ELF32symbol; + +typedef struct { + uint32_t name; + uint8_t info, other; + uint16_t sectidx; + uint64_t value, size; +} ELF64symbol; + +typedef struct { + ELF32header hdr; + ELF32sectheader sect[6]; + ELF32symbol sym[2]; + uint8_t space[4096]; +} ELF32obj; + +typedef struct { + ELF64header hdr; + ELF64sectheader sect[6]; + ELF64symbol sym[2]; + uint8_t space[4096]; +} ELF64obj; +]] + +local is64_arch = { + ['x64'] = true, + ['arm64'] = true, + ['arm64be'] = true, + ['ppc'] = false, + ['mips'] = false, +} + +local is64 = is64_arch[jit.arch] or false + +local function create_obj_file(name) + local elf_filename = os.tmpname() .. '.obj' + local lua_path = os.getenv('LUA_PATH') + local lua_bin = require('utils').luacmd(arg):match('%S+') + local cmd_fmt = 'LUA_PATH="%s" %s -b -n "%s" -e "print()" %s' + local cmd = (cmd_fmt):format(lua_path, lua_bin, name, elf_filename) + local ret = os.execute(cmd) + assert(ret == 0, 'create an object file') + return elf_filename +end + +-- Reads a file located in a specified path and returns its content. +local function read_file(path) + local file = assert(io.open(path), 'cannot open an object file') + local content = file:read('*a') + file:close() + return content +end + +-- Parses a buffer in an ELF format and returns an offset and a size of strtab +-- and symtab sections. +local function read_elf(elf_content) + local ELFobj_type = ffi.typeof(is64 and 'ELF64obj *' or 'ELF32obj *') + local ELFsectheader_type = ffi.typeof(is64 and 'ELF64sectheader *' or 'ELF32sectheader *') + local elf = ffi.cast(ELFobj_type, elf_content) + local symtab_hdr, strtab_hdr + -- Iterate by section headers. + for i = 0, elf.hdr.shnum do + local sec = ffi.cast(ELFsectheader_type, elf.sect[i]) + if sec.type == SHT_SYMTAB then + symtab_hdr = sec + strtab_hdr = ffi.cast(ELFsectheader_type, elf.sect[symtab_hdr.link]) + break + end + end + + assert(strtab_hdr ~= nil, 'section .strtab was not found') + assert(symtab_hdr ~= nil, 'section .symtab was not found') + + return strtab_hdr, symtab_hdr +end + +test:plan(3) + +local elf_filename = create_obj_file(module_name) +local elf_content = read_file(elf_filename) +assert(#elf_content ~= 0, 'cannot read an object file') + +local strtab, symtab = read_elf(elf_content) +local strtab_size = tonumber(strtab.size) +local strtab_offset = tonumber(strtab.ofs) +local symtab_size = tonumber(symtab.size) +local sym_cnt = tonumber(symtab_size / symtab.entsize) +assert(sym_cnt ~= 0, 'number of symbols is zero') + +test:is(strtab_size, expected_strtab_size, 'check .strtab size') +test:is(strtab_offset, expected_strtab_offset, 'check .strtab offset') + +local strtab_str = string.sub(elf_content, strtab_offset, strtab_offset + strtab_size) + +local strtab_p = ffi.cast('char *', strtab_str) +local sym_name_expected = LJBC_PREFIX .. module_name +local sym_is_found = false +for i = 1, sym_cnt do + local sym_name = ffi.string(strtab_p + i) + if sym_name_expected == sym_name then + sym_is_found = true + break + end +end + +test:ok(sym_is_found == true, 'symbol is found') + +local ret = os.remove(elf_filename) +assert(ret == true, 'cannot remove an object file') + +os.exit(test:check() and 0 or 1) -- 2.34.1
next reply other threads:[~2023-05-30 8:09 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-30 8:09 Sergey Bronnikov via Tarantool-patches [this message] 2023-05-30 9:05 ` Maxim Kokryashkin via Tarantool-patches 2023-05-31 14:50 ` Sergey Bronnikov via Tarantool-patches 2023-06-06 12:55 ` Sergey Kaplun via Tarantool-patches 2023-06-06 12:31 ` Sergey Kaplun via Tarantool-patches 2023-06-06 14:14 ` Sergey Bronnikov via Tarantool-patches 2023-07-04 17:09 ` Igor Munkin via Tarantool-patches
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