elf.lua: decode program headers
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233a69e859
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B715679E3A361BE6
195
plugins/elf.lua
195
plugins/elf.lua
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@ -20,6 +20,82 @@ local detect = function (c)
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return c:read (4) == "\x7FELF"
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end
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local ph_type_table = {
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[0] = "unused segment",
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[1] = "loadable segment",
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[2] = "dynamic linking information",
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[3] = "interpreter pathname",
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[4] = "auxiliary information",
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[5] = "reserved",
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[6] = "the program header table itself",
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[7] = "the thread-local storage template"
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}
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local xform_ph_flags = function (u32)
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local info = {}
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if u32 & 4 ~= 0 then table.insert (info, "read") end
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if u32 & 2 ~= 0 then table.insert (info, "write") end
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if u32 & 1 ~= 0 then table.insert (info, "execute") end
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local junk = u32 & ~7
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if junk ~= 0 then
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table.insert (info, ("unknown: %#x"):format (junk))
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end
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if #info == 0 then return 0 end
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local result = info[1]
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for i = 2, #info do result = result .. ", " .. info[i] end
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return result
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end
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local decode_ph = function (elf, c)
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local ph = {}
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ph.type = c:u32 ("type: %s", function (u32)
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-- TODO: there are more known weird values and ranges
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name = ph_type_table[u32]
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if name then return name end
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return "unknown: %#x", u32
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end)
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if elf.class == 2 then ph.flags = c:u32 ("flags: %s", xform_ph_flags) end
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ph.offset = elf.uwide (c, "offset in file: %#x")
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ph.vaddr = elf.uwide (c, "virtual address: %#x")
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ph.paddr = elf.uwide (c, "physical address: %#x")
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ph.filesz = elf.uwide (c, "size in file: %d")
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ph.memsz = elf.uwide (c, "sise in memory: %d")
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if elf.class == 1 then ph.flags = c:u32 ("flags: %s", xform_ph_flags) end
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ph.align = elf.uwide (c, "alignment: %d")
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end
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local decode_sh = function (elf, c)
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-- TODO
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end
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local abi_table = {
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[0] = "UNIX System V ABI",
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[1] = "HP-UX operating system",
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[2] = "NetBSD",
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[3] = "GNU/Linux",
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[4] = "GNU/Hurd",
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[6] = "Solaris",
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[7] = "AIX",
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[8] = "IRIX",
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[9] = "FreeBSD",
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[10] = "TRU64 UNIX",
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[11] = "Novell Modesto",
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[12] = "OpenBSD",
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[13] = "OpenVMS",
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[14] = "Hewlett-Packard Non-Stop Kernel",
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[15] = "AROS",
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[16] = "FenixOS",
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[17] = "Nuxi CloudABI",
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[64] = "Bare-metal TMS320C6000",
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[64] = "AMD HSA runtime",
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[65] = "Linux TMS320C6000",
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[97] = "ARM",
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[255] = "Standalone (embedded) application"
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}
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local type_table = {
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[0] = "no file type",
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[1] = "relocatable file",
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@ -210,74 +286,20 @@ local machine_table = {
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[247] = "Linux kernel bpf virtual machine"
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}
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local decode32 = function (c)
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-- TODO: like the 64-bit version, maybe try to merge the code somehow
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end
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local decode64 = function (c)
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local type = c:u16 ("type of file: %s", function (u16)
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name = type_table[u16]
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if name then return name end
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return "unknown: %d", u16
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end)
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local machine = c:u16 ("required architecture: %s", function (u16)
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name = machine_table[u16]
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if name then return name end
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return "unknown: %d", u16
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end)
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local version = c:u32 ("version: %d")
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local entry = c:u64 ("program entry address: %#x")
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local ph_offset = c:u64 ("program header table offset: %#x")
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local sh_offset = c:u64 ("section header table offset: %#x")
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local flags = c:u32 ("processor-specific flags: %#x")
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local eh_size = c:u16 ("ELF header size: %d")
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local ph_entry_size = c:u16 ("program header size: %d")
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local ph_number = c:u16 ("program header count: %d")
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local sh_entry_size = c:u16 ("section header size: %d")
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local sh_number = c:u16 ("section header count: %d")
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local sh_string_index = c:u16 ("section header index for strings: %d")
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-- TODO: decode all sections as well, see man 5 elf,
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-- /usr/include/elf.h and /usr/include/llvm/Support/ELF.h
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end
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local abi_table = {
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[0] = "UNIX System V ABI",
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[1] = "HP-UX operating system",
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[2] = "NetBSD",
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[3] = "GNU/Linux",
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[4] = "GNU/Hurd",
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[6] = "Solaris",
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[7] = "AIX",
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[8] = "IRIX",
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[9] = "FreeBSD",
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[10] = "TRU64 UNIX",
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[11] = "Novell Modesto",
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[12] = "OpenBSD",
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[13] = "OpenVMS",
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[14] = "Hewlett-Packard Non-Stop Kernel",
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[15] = "AROS",
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[16] = "FenixOS",
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[17] = "Nuxi CloudABI",
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[64] = "Bare-metal TMS320C6000",
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[64] = "AMD HSA runtime",
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[65] = "Linux TMS320C6000",
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[97] = "ARM",
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[255] = "Standalone (embedded) application"
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}
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local decode = function (c)
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assert (c.position == 1)
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if not detect (c ()) then error ("not an ELF file") end
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local p = c.position, c:read (4)
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c (p, p + 3):mark ("ELF magic")
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local class = c:u8 ("ELF class: %s", function (u8)
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local elf = {}
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elf.class = c:u8 ("ELF class: %s", function (u8)
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if u8 == 1 then return "32-bit" end
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if u8 == 2 then return "64-bit" end
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return "invalid: %d", u8
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end)
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local data = c:u8 ("ELF data: %s", function (u8)
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elf.data = c:u8 ("ELF data: %s", function (u8)
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if u8 == 1 then
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c.endianity = "le"
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return "little-endian"
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@ -288,22 +310,65 @@ local decode = function (c)
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end
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return "invalid: %d", u8
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end)
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local version = c:u8 ("ELF version: %d")
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local abi = c:u8 ("OS ABI: %s", function (u8)
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elf.version = c:u8 ("ELF version: %d")
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elf.abi = c:u8 ("OS ABI: %s", function (u8)
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name = abi_table[u8]
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if name then return name end
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return "unknown: %d", u8
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end)
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local abi_version = c:u8 ("OS ABI version: %d")
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elf.abi_version = c:u8 ("OS ABI version: %d")
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-- The padding is reserved, no big sense in marking it
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local padding = c:read (7)
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-- We cannot decode anything further as we don't know how
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if data ~= 1 and data ~= 2 then return end
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-- We cannot decode anything further if we don't know endianity
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if elf.data ~= 1 and elf.data ~= 2 then return end
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if class == 1 then decode32 (c) end
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if class == 2 then decode64 (c) end
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-- And the same applies to the class
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if elf.class == 1 then elf.uwide = c.u32
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elseif elf.class == 2 then elf.uwide = c.u64
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else return end
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elf.type = c:u16 ("type of file: %s", function (u16)
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name = type_table[u16]
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if name then return name end
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return "unknown: %d", u16
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end)
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elf.machine = c:u16 ("required architecture: %s", function (u16)
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name = machine_table[u16]
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if name then return name end
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return "unknown: %d", u16
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end)
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elf.version = c:u32 ("version: %d")
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elf.entry = elf.uwide (c, "program entry address: %#x")
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elf.ph_offset = elf.uwide (c, "program header table offset: %#x")
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elf.sh_offset = elf.uwide (c, "section header table offset: %#x")
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elf.flags = c:u32 ("processor-specific flags: %#x")
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elf.eh_size = c:u16 ("ELF header size: %d")
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c (1, elf.eh_size):mark ("ELF header")
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elf.ph_entry_size = c:u16 ("program header size: %d")
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elf.ph_number = c:u16 ("program header count: %d")
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elf.sh_entry_size = c:u16 ("section header size: %d")
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elf.sh_number = c:u16 ("section header count: %d")
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elf.sh_string_index = c:u16 ("section header index for strings: %d")
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-- TODO: decode all headers as well, see man 5 elf,
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-- /usr/include/elf.h and /usr/include/llvm/Support/ELF.h
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for i = 1, elf.ph_number do
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local start = elf.ph_offset + (i - 1) * elf.ph_entry_size
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local ph = c (1 + start, start + elf.ph_entry_size)
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ph:mark ("ELF program header %d", i - 1)
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decode_ph (elf, ph)
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end
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-- TODO: we will need to decode "sh_string_index" first to get names
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for i = 1, elf.sh_number do
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local start = elf.sh_offset + (i - 1) * elf.sh_entry_size
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local sh = c (1 + start, start + elf.sh_entry_size)
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sh:mark ("ELF section header %d", i - 1)
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decode_sh (elf, sh)
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end
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end
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hex.register { type="elf", detect=detect, decode=decode }
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