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* [Tarantool-patches] [PATCH luajit v2 1/1] Fix saved bytecode encapsulated in ELF objects.
@ 2023-05-30  8:09 Sergey Bronnikov via Tarantool-patches
  2023-05-30  9:05 ` Maxim Kokryashkin via Tarantool-patches
                   ` (2 more replies)
  0 siblings, 3 replies; 7+ messages in thread
From: Sergey Bronnikov via Tarantool-patches @ 2023-05-30  8:09 UTC (permalink / raw)
  To: tarantool-patches, Sergey Kaplun, Maxim Kokryashkin

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


^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2023-07-04 17:19 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-05-30  8:09 [Tarantool-patches] [PATCH luajit v2 1/1] Fix saved bytecode encapsulated in ELF objects Sergey Bronnikov via Tarantool-patches
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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