Commit 51db8f87 authored by PoroCYon's avatar PoroCYon Committed by PoroCYon
Browse files

reorganize everything in a single invocation (take 2)

parent 09acda91
OBJDIR := obj
BINDIR := bin
SRCDIR := rt
PYDIR := src
LDDIR := ld
TESTDIR:= test
NASM ?= nasm
BITS ?= $(shell getconf LONG_BIT)
# -mpreferred-stack-boundary=3 messes up the stack and kills SSE!
......@@ -23,58 +23,38 @@ CXXOPTFLAGS=$(COPTFLAGS) -fno-exceptions \
CFLAGS=-Wall -Wextra -Wpedantic -std=gnu11 -nostartfiles -fno-PIC $(COPTFLAGS) #-DUSE_DL_FINI
CXXFLAGS=-Wall -Wextra -Wpedantic -std=c++11 $(CXXOPTFLAGS) -nostartfiles -fno-PIC
ASFLAGS=-I $(SRCDIR)/
LDFLAGS_ :=
CFLAGS += -m$(BITS) $(shell pkg-config --cflags sdl2)
CXXFLAGS += -m$(BITS) $(shell pkg-config --cflags sdl2)
ifeq ($(BITS),32)
# I think prescott is basically nocona but 32-bit only, althought I'm not sure
# if this one is optimal
CFLAGS += -m32 -march=prescott
LDFLAGS += -m32
ASFLAGS += -f elf32
LDFLAGS_ := -m32
CFLAGS += -march=prescott
else
# I've heard nocona gets slightly smaller binaries than core2
CFLAGS += -m64 -march=nocona
LDFLAGS += -m64
ASFLAGS += -f elf64
LDFLAGS_ := -m64
CFLAGS += -march=nocona
endif
LDFLAGS += -nostartfiles -nostdlib
LDFLAGS_ := $(LDFLAGS_) -T $(LDDIR)/link.ld -Wl,--oformat=binary $(LDFLAGS)
CFLAGS += -m$(BITS) $(shell pkg-config --cflags sdl2)
CXXFLAGS += -m$(BITS) $(shell pkg-config --cflags sdl2)
LIBS = $(filter-out -pthread,$(shell pkg-config --libs sdl2)) -lX11 -lc #-lGL
LIBS=-lc
PWD ?= .
SMOLFLAGS +=
ASFLAGS += -DALIGN_STACK -DUSE_INTERP #-DUSE_DNLOAD_LOADER
#-DUSE_DNLOAD_LOADER #-DUSE_DT_DEBUG #-DUSE_DL_FINI #-DNO_START_ARG #-DUNSAFE_DYNAMIC
SMOLFLAGS = --smolrt "$(PWD)/rt" --smolld "$(PWD)/ld" \
-falign-stack -fuse-interp \
--verbose #--keeptmp
# -fuse-dnload-loader -fskip-zero-value -fuse-nx -fskip-entries -fuse-dt-debug
# -fuse-dl-fini -fno-start-arg -funsafe-dynamic
NASM ?= nasm
PYTHON3 ?= python3
all: $(BINDIR)/hello-crt $(BINDIR)/sdl-crt $(BINDIR)/flag $(BINDIR)/hello-_start
LIBS += $(filter-out -pthread,$(shell pkg-config --libs sdl2)) -lX11 #-lGL
clean:
@$(RM) -vrf $(OBJDIR) $(BINDIR)
%/:
@mkdir -vp "$@"
# TODO: handle this in a more graceful and future-proof way!
ifneq ($(findstring (GCC) 9,$(shell $(CC) --version)),)
INCLINKOPT := -flinker-output=nolto-rel
else
ifneq ($(findstring (GCC) 10,$(shell $(CC) --version)),)
INCLINKOPT := -flinker-output=nolto-rel
else
INCLINKOPT :=
endif
endif
.SECONDARY:
$(OBJDIR)/%.lto.o: $(SRCDIR)/%.c $(OBJDIR)/
......@@ -87,26 +67,13 @@ $(OBJDIR)/%.o: $(SRCDIR)/%.c $(OBJDIR)/
$(OBJDIR)/%.o: $(TESTDIR)/%.c $(OBJDIR)/
$(CC) $(CFLAGS) -c "$<" -o "$@"
$(OBJDIR)/%.start.o: $(OBJDIR)/%.lto.o $(OBJDIR)/crt1.lto.o
$(CC) $(LDFLAGS) -r $(INCLINKOPT) -o "$@" $^
$(OBJDIR)/symbols.%.asm: $(OBJDIR)/%.o
$(PYTHON3) $(PYDIR)/smol.py $(SMOLFLAGS) $(LIBS) "$<" "$@"
$(OBJDIR)/stub.%.o: $(OBJDIR)/symbols.%.asm $(SRCDIR)/header32.asm \
$(SRCDIR)/loader32.asm
$(NASM) $(ASFLAGS) $< -o $@
$(OBJDIR)/stub.%.start.o: $(OBJDIR)/symbols.%.start.asm $(SRCDIR)/header32.asm \
$(SRCDIR)/loader32.asm
$(NASM) $(ASFLAGS) $< -o $@
$(BINDIR)/%: $(OBJDIR)/%.o $(OBJDIR)/stub.%.o $(BINDIR)/
$(CC) -Wl,-Map=$(BINDIR)/$*.map $(LDFLAGS_) $(OBJDIR)/$*.o $(OBJDIR)/stub.$*.o -o "$@"
./rmtrailzero.py "$@" "$(OBJDIR)/$(notdir $@)" && mv "$(OBJDIR)/$(notdir $@)" "$@" && chmod +x "$@"
$(BINDIR)/%: $(OBJDIR)/%.o $(BINDIR)/
$(PYTHON3) ./smold.py $(SMOLFLAGS) $(LIBS) "$<" "$@"
$(PYTHON3) ./smoltrunc.py "$@" "$(OBJDIR)/$(notdir $@)" && mv "$(OBJDIR)/$(notdir $@)" "$@" && chmod +x "$@"
$(BINDIR)/%-crt: $(OBJDIR)/%.start.o $(OBJDIR)/stub.%.start.o $(BINDIR)/
$(CC) -Wl,-Map=$(BINDIR)/$*-crt.map $(LDFLAGS_) $(OBJDIR)/$*.start.o $(OBJDIR)/stub.$*.start.o -o "$@"
$(BINDIR)/%-crt: $(OBJDIR)/%.lto.o $(OBJDIR)/crt1.lto.o $(BINDIR)/
$(PYTHON3) ./smold.py $(SMOLFLAGS) --ldflags=-Wl,-Map=$(BINDIR)/$*-crt.map $(LIBS) "$<" $(OBJDIR)/crt1.lto.o "$@"
$(PYTHON3) ./smoltrunc.py "$@" "$(OBJDIR)/$(notdir $@)" && mv "$(OBJDIR)/$(notdir $@)" "$@" && chmod +x "$@"
.PHONY: all clean
......@@ -6,56 +6,33 @@ PoC by Shiz, bugfixing and 64-bit version by PoroCYon.
## Dependencies
* A C compiler (preferably GCC), GNU ld, binutils, GNU make, ...
* GCC (not clang, as the latter doesn't support `nolto-rel` output), GNU ld,
binutils, GNU make, ...
* nasm 2.13 or newer
* scanelf from pax-utils
* `scanelf` from `pax-utils`
* Python 3
## Usage
***NOTE***: Your entrypoint (`_start`) ***must*** be in a section called
`.text.startup._start`! Otherwise, the linker script will fail silently, and
the smol startup/symbol resolving code will jump to an undefined location.
```sh
./smol.py -lfoo -lbar input.o... smol-output.asm
nasm -I src/ [-Doption ...] -o nasm-output.o smol-output.asm
ld -T ld/link.ld --oformat=binary -o output.elf nasm-output.o input.o...
# or cc -T ld/link.ld -Wl,--oformat=binary -o output.elf nasm-output.o input.o...
./smold.py --use_interp --align_stack [--opts...] -lfoo -lbar input.o... output.elf
```
* `USE_INTERP`: Include an interp segment in the output ELF file. If not, the
dynamic linker **must** be invoked *explicitely*! (You probably want to
enable this.) Costs the size of a phdr plus the size of the interp string.
* `ALIGN_STACK`: *64-bit only*: realign the stack so that SSE instructions
won't segfault. Costs 1 byte.
* `USE_NX`: Don't use `RWE` segments at all. Not very well tested. Costs the
size of 1 phdr, plus some extra stuff on `i386`. Don't forget to pass `-n`
to `smol.py` as well.
* `USE_DL_FINI`: keep track of the `_dl_fini` function and pass it to your
`_start`. Costs 2 bytes, plus maybe a few more depending on how it's passed
to `__libc_start_main`.
* `USE_DT_DEBUG`: retrieve the `struct link_map` from the `r_debug` linker
data (which is placed at `DT_DEBUG` at startup) instead of exploiting data
leakage from `_dt_start_user`. Might be more compatible and compressable, but
strictly worse size-wise by 10 (i386) or 3 (x86_64) bytes.
* `SKIP_ENTRIES`: skip the first two entries of the `struct link_map`, which
represent the main binary and the vDSO. Costs around 5 bytes.
* `USE_DNLOAD_LOADER`: use the symbol loading mechanism as used in dnload (i.e.
traverse the symtab of the imported libraries). Slightly larger, but probably
better compressable and more compatible with other libcs and future versions
of glibc.
* `NO_START_ARG`: *don't* pass the stack pointer to `_start` as the first arg.
Will make it unable to read argc/argv/environ, but gives you 3 bytes.
* `SKIP_ZERO_VALUE`: skip a `Sym` with a `st_value` field of `0`. If this isn't
enabled, weak symbols etc. might be imported instead of the real ones,
causing breakage. Many libraries don't have weak symbols at all, though.
Costs 4 (i386) or 5 (x86_64) bytes.
```
usage: smol.py [-h] [-m TARGET] [-l LIB] [-L DIR] [--nasm NASM] [--cc CC]
[--scanelf SCANELF] [--readelf READELF]
input [input ...] output
usage: smold.py [-h] [-m TARGET] [-l LIB] [-L DIR] [-s] [-n] [-d] [-fuse-interp] [-falign-stack] [-fuse-nx]
[-fuse-dnload-loader] [-fskip-zero-value] [-fuse-dt-debug] [-fuse-dl-fini] [-fskip-entries]
[-fno-start-arg] [-funsafe-dynamic] [--nasm NASM] [--cc CC] [--scanelf SCANELF] [--readelf READELF]
[--cflags CFLAGS] [--asflags ASFLAGS] [--ldflags LDFLAGS] [--smolrt SMOLRT] [--smolld SMOLLD]
[--verbose] [--keeptmp]
input [input ...] output
positional arguments:
input input object file
output output nasm file
output output binary
optional arguments:
-h, --help show this help message and exit
......@@ -64,14 +41,45 @@ optional arguments:
-l LIB, --library LIB
libraries to link against
-L DIR, --libdir DIR directories to search libraries in
-s, --hash16 Use 16-bit (BSD) hashes instead of 32-bit djb2 hashes. Implies -fuse-dnload-loader
-n, --nx Use NX (i.e. don't use RWE pages). Costs the size of one phdr, plus some extra bytes on
i386.
-d, --det Make the order of imports deterministic (default: just use whatever binutils throws at us)
-fuse-interp Include a program interpreter header (PT_INTERP). If not enabled, ld.so has to be invoked
manually by the end user.
-falign-stack Align the stack before running user code (_start). If not enabled, this has to be done
manually. Costs 1 byte.
-fuse-nx Don't use one big RWE segment, but use separate RW and RE ones. Use this to keep strict
kernels (PaX/grsec) happy. Costs at least the size of one program header entry.
-fuse-dnload-loader Use a dnload-style loader for resolving symbols, which doesn't depend on
nonstandard/undocumented ELF and ld.so features, but is slightly larger. If not enabled, a
smaller custom loader is used which assumes glibc.
-fskip-zero-value Skip an ELF symbol with a zero address (a weak symbol) when parsing libraries at runtime.
Try enabling this if you're experiencing sudden breakage. However, many libraries don't use
weak symbols, so this doesn't often pose a problem. Costs ~5 bytes.
-fuse-dt-debug Use the DT_DEBUG Dyn header to access the link_map, which doesn't depend on
nonstandard/undocumented ELF and ld.so features. If not enabled, the link_map is accessed
using data leaked to the entrypoint by ld.so, which assumes glibc. Costs ~10 bytes.
-fuse-dl-fini Pass _dl_fini to the user entrypoint, which should be done to properly comply with all
standards, but is very often not needed at all. Costs 2 bytes.
-fskip-entries Skip the first two entries in the link map (resp. ld.so and the vDSO). Speeds up symbol
resolving, but costs ~5 bytes.
-fno-start-arg Don't pass a pointer to argc/argv/envp to the entrypoint using the standard calling
convention. This means you need to read these yourself in assembly if you want to use them!
(envp is a preprequisite for X11, because it needs $DISPLAY.) Frees 3 bytes.
-funsafe-dynamic Don't end the ELF Dyn table with a DT_NULL entry. This might cause ld.so to interpret the
entire binary as the Dyn table, so only enable this if you're sure this won't break things!
--nasm NASM which nasm binary to use
--cc CC which cc binary to use
--cc CC which cc binary to use (MUST BE GCC!)
--scanelf SCANELF which scanelf binary to use
--readelf READELF which readelf binary to use
-n, --nx Use NX (i.e. don't use RWE pages). Costs the size of
one phdr, plus some extra bytes on i386. Don't forget
to pass -DUSE_NX to the assembly loader as well!
--cflags CFLAGS Flags to pass to the C compiler for the relinking step
--asflags ASFLAGS Flags to pass to the assembler when creating the ELF header and runtime startup code
--ldflags LDFLAGS Flags to pass to the linker for the final linking step
--smolrt SMOLRT Directory containing the smol runtime sources
--smolld SMOLLD Directory containing the smol linker scripts
--verbose Be verbose about what happens and which subcommands are invoked
--keeptmp Keep temp files (only useful for debugging)
```
A minimal crt (and `_start` funcion) are provided in case you want to use `main`.
......@@ -83,9 +91,6 @@ imported by a `smol`-ified binary. This can thus be used to detect user mistakes
during dynamic linking. (Think of it as an equivalent of `ldd`, except that it
also checks whether the imported functions are present as well.)
***NOTE***: `smoldd.py` currently doesn't support 64-bit binaries anymore, as
there's currently no (good) way of retrieving the symbol hash table anymore.
## Internal workings
`smol.py` inspects the input object files for needed library files and symbols.
......@@ -99,7 +104,7 @@ works for glibc): on both i386 and x86_64, the linker startup code
(`_dl_start_user`) leaks the global `struct link_map` to the user code:
on i386, a pointer to it is passed directly through `eax`:
```s
```asm
# (eax, edx, ecx, esi) = (_dl_loaded, argc, argv, envp)
movl _rtld_local@GOTOFF(%ebx), %eax
## [ boring stuff... ]
......
import os.path
import subprocess
import sys
from .parse import *
from .shared import eprintf
def cc_relink_objs(verbose, cc_bin, arch, inputs, output, cflags):
archflag = '-m64' if arch == "x86_64" else '-m32'
cctyp, ccver = get_cc_version(cc_bin)
assert cctyp == "gcc", "A GCC compiler is needed for relinking objects!"
relink_arg = "-flinker-output=rel" if ccver < (9,0) else "-flinker-output=nolto-rel"
args = [cc_bin, archflag, '-nostartfiles', '-nostdlib', \
'-r', relink_arg, '-o', output] + cflags + inputs
if verbose: eprintf("cc: %s" % repr(args))
subprocess.check_call(args, stdout=subprocess.DEVNULL)
def nasm_assemble_elfhdr(verbose, nasm_bin, arch, rtdir, intbl, output, asflags):
if rtdir[-1] != '/': rtdir = rtdir + '/'
archflag = 'elf64' if arch == "x86_64" else 'elf32'
args = [nasm_bin, '-I', rtdir, '-f', archflag] + asflags + [intbl, '-o', output]
if verbose: eprintf("nasm: %s" % repr(args))
subprocess.check_call(args, stdout=subprocess.DEVNULL)
def ld_link_final(verbose, cc_bin, arch, lddir, inobjs, output, ldflags):
archflag = '-m64' if arch == "x86_64" else '-m32'
args = [cc_bin, archflag, '-T', lddir+'/link.ld', \
'-Wl,--oformat=binary', '-nostartfiles', '-nostdlib', \
'-o', output] + inobjs + ldflags
if verbose: eprintf("ld: %s" % repr(args))
subprocess.check_call(args, stdout=subprocess.DEVNULL)
......@@ -2,7 +2,7 @@
import sys
from collections import OrderedDict
from smolshared import *
from .shared import *
def sort_imports(libraries, hashfn):
#eprintf("in: " + str(libraries))
......@@ -34,9 +34,8 @@ def output_x86(libraries, nx, h16, outf, det):
for sym, reloc in symrels: usedrelocs.add(reloc)
if not(nx) and 'R_386_PC32' in usedrelocs and 'R_386_GOT32X' in usedrelocs:
eprintf("Using a mix of R_386_PC32 and R_386_GOT32X relocations! "+\
error("Using a mix of R_386_PC32 and R_386_GOT32X relocations! "+\
"Please change a few C compiler flags and recompile your code.")
exit(1)
use_jmp_bytes = not nx and 'R_386_PC32' in usedrelocs
......@@ -111,8 +110,7 @@ global {name}
def output_amd64(libraries, nx, h16, outf, det):
if h16:
eprintf("--hash16 not supported yet for x86_64 outputs.")
exit(1)
error("--hash16 not supported yet for x86_64 outputs.")
if nx: outf.write('%define USE_NX 1\n')
# if h16: outf.write('%define USE_HASH16 1\n')
......@@ -155,8 +153,7 @@ dynamic.end:
for sym, reloc in symrels:
if reloc not in ['R_X86_64_PLT32', 'R_X86_64_GOTPCRELX', \
'R_X86_64_REX_GOTPCRELX', 'R_X86_64_GOTPCREL']:
eprintf('Relocation type ' + reloc + ' of symbol ' + sym + ' unsupported!')
sys.exit(1)
error('Relocation type ' + reloc + ' of symbol ' + sym + ' unsupported!')
if reloc in ['R_X86_64_GOTPCRELX', 'R_X86_64_REX_GOTPCRELX', \
'R_X86_64_GOTPCREL']:
......@@ -192,6 +189,5 @@ def output(arch, libraries, nx, h16, outf, det):
if arch == 'i386': output_x86(libraries, nx, h16, outf, det)
elif arch == 'x86_64': output_amd64(libraries, nx, h16, outf, det)
else:
eprintf("E: cannot emit for arch '" + str(arch) + "'")
sys.exit(1)
error("E: cannot emit for arch '" + str(arch) + "'")
......@@ -5,7 +5,7 @@ import subprocess
import struct
import sys
from smolshared import *
from .shared import *
def decide_arch(inpfiles):
archs=set({})
......@@ -20,8 +20,7 @@ def decide_arch(inpfiles):
archs.add(machnum)
if len(archs) != 1:
eprintf("Input files have multiple architectures, can't link this...")
sys.exit(1)
error("Input files have multiple architectures, can't link this...")
archn = list(archs)[0]
......@@ -48,24 +47,41 @@ def build_reloc_typ_table(reo):
return relocs
def get_needed_syms(readelf_bin, inpfiles):
output = subprocess.check_output([readelf_bin, '-s', '-W']+inpfiles,
def has_lto_object(readelf_bin, files):
for x in files:
with open(x,'rb') as f:
if f.read(2) == b'BC': # LLVM bitcode! --> clang -flto
return True
output = subprocess.check_output([readelf_bin, '-s', '-W'] + files,
stderr=subprocess.DEVNULL)
curfile = files[0]
for entry in output.decode('utf-8').splitlines():
stuff = entry.split()
if len(stuff)<2: continue
if stuff[0] == "File:": curfile = stuff[1]
if "__gnu_lto_" in entry or ".gnu.lto" in entry: # assuming nobody uses a symbol called "__gnu_lto_" ...
return True
return False
def get_needed_syms(readelf_bin, inpfile):
output = subprocess.check_output([readelf_bin, '-s', '-W',inpfile],
stderr=subprocess.DEVNULL)
outrel = subprocess.check_output([readelf_bin, '-r', '-W']+inpfiles,
outrel = subprocess.check_output([readelf_bin, '-r', '-W',inpfile],
stderr=subprocess.DEVNULL)
relocs = build_reloc_typ_table(outrel)
curfile = inpfiles[0]
curfile = inpfile
syms=set({})
for entry in output.decode('utf-8').splitlines():
stuff = entry.split()
if len(stuff)<2: continue
if stuff[0] == "File:": curfile = stuff[1]
if len(stuff)<8: continue
if stuff[7].startswith("__gnu_lto_"): # yikes, an LTO object
eprintf("{} is an LTO object file, can't use this!".format(curfile))
exit(1)
#if stuff[7].startswith("__gnu_lto_"): # yikes, an LTO object
# error("{} is an LTO object file, can't use this!".format(curfile))
if stuff[4] == "GLOBAL" and stuff[6] == "UND" and len(stuff[7])>0 \
and stuff[7] in relocs:
syms.add((stuff[7], relocs[stuff[7]]))
......@@ -105,6 +121,21 @@ def get_cc_paths(cc_bin):
return paths
def get_cc_version(cc_bin):
bak = os.environ.copy()
os.environ['LANG'] = "C" # DON'T output localized search dirs!
output = subprocess.check_output([cc_bin, '--version'],
stderr=subprocess.DEVNULL)
os.environ = bak
lines = output.decode('utf-8').splitlines()
if "Free Software Foundation" in lines[1]: # GCC
verstr = lines[0].split()[-1]
return ("gcc", tuple(map(int, verstr.split('.'))))
else: # assume clang
verstr = lines[0].split()[-1]
return ("clang", tuple(map(int, verstr.split('.'))))
def is_valid_elf(f): # Good Enough(tm)
with open(f, 'rb') as ff: return ff.read(4) == b'\x7FELF'
......@@ -117,8 +148,7 @@ def find_lib(spaths, wanted):
#for f in glob.glob(glob.escape(p) + '/lib' + wanted + '.a' ): return f
#for f in glob.glob(glob.escape(p) + '/' + wanted + '.a' ): return f
eprintf("E: couldn't find library '" + wanted + "'.")
sys.exit(1)
error("E: couldn't find library '" + wanted + "'.")
def find_libs(spaths, wanted): return map(lambda l: find_lib(spaths, l), wanted)
......
......@@ -21,3 +21,7 @@ def hash_djb2(s):
def eprintf(*args, **kwargs): print(*args, file=sys.stderr, **kwargs)
def error(*args, **kwargs):
eprintf(*args, **kwargs)
sys.exit(1)
#!/usr/bin/env python3
import argparse
import glob
import itertools
import os, os.path
import shutil
import subprocess
import sys
import tempfile
from smol.shared import *
from smol.parse import *
from smol.emit import *
from smol.cnl import *
def main():
parser = argparse.ArgumentParser()
parser.add_argument('-m', '--target', default='', \
help='architecture to generate asm code for (default: auto)')
parser.add_argument('-l', '--library', default=[], metavar='LIB', action='append', \
help='libraries to link against')
parser.add_argument('-L', '--libdir', default=[], metavar='DIR', action='append', \
help="directories to search libraries in")
parser.add_argument('-s', '--hash16', default=False, action='store_true', \
help="Use 16-bit (BSD) hashes instead of 32-bit djb2 hashes. "+\
"Implies -fuse-dnload-loader")
parser.add_argument('-n', '--nx', default=False, action='store_true', \
help="Use NX (i.e. don't use RWE pages). Costs the size of one phdr, "+\
"plus some extra bytes on i386.")
parser.add_argument('-d', '--det', default=False, action='store_true', \
help="Make the order of imports deterministic (default: just use " + \
"whatever binutils throws at us)")
parser.add_argument('-fuse-interp', default=False, action='store_true', \
help="Include a program interpreter header (PT_INTERP). If not " +\
"enabled, ld.so has to be invoked manually by the end user.")
parser.add_argument('-falign-stack', default=False, action='store_true', \
help="Align the stack before running user code (_start). If not " + \
"enabled, this has to be done manually. Costs 1 byte.")
parser.add_argument('-fuse-nx', default=False, action='store_true', \
help="Don't use one big RWE segment, but use separate RW and RE ones."+\
" Use this to keep strict kernels (PaX/grsec) happy. Costs at "+\
"least the size of one program header entry.")
parser.add_argument('-fuse-dnload-loader', default=False, action='store_true', \
help="Use a dnload-style loader for resolving symbols, which doesn't "+\
"depend on nonstandard/undocumented ELF and ld.so features, but "+\
"is slightly larger. If not enabled, a smaller custom loader is "+\
"used which assumes glibc.")
parser.add_argument('-fskip-zero-value', default=False, action='store_true', \
help="Skip an ELF symbol with a zero address (a weak symbol) when "+\
"parsing libraries at runtime. Try enabling this if you're "+\
"experiencing sudden breakage. However, many libraries don't use "+\
"weak symbols, so this doesn't often pose a problem. Costs ~5 bytes.")
parser.add_argument('-fuse-dt-debug', default=False, action='store_true', \
help="Use the DT_DEBUG Dyn header to access the link_map, which doesn't"+\
" depend on nonstandard/undocumented ELF and ld.so features. If "+\
"not enabled, the link_map is accessed using data leaked to the "+\
"entrypoint by ld.so, which assumes glibc. Costs ~10 bytes.")
parser.add_argument('-fuse-dl-fini', default=False, action='store_true', \
help="Pass _dl_fini to the user entrypoint, which should be done to "+\
"properly comply with all standards, but is very often not "+\
"needed at all. Costs 2 bytes.")
parser.add_argument('-fskip-entries', default=False, action='store_true', \
help="Skip the first two entries in the link map (resp. ld.so and "+\
"the vDSO). Speeds up symbol resolving, but costs ~5 bytes.")
parser.add_argument('-fno-start-arg', default=False, action='store_true', \
help="Don't pass a pointer to argc/argv/envp to the entrypoint using "+\
"the standard calling convention. This means you need to read "+\
"these yourself in assembly if you want to use them! (envp is "+\
"a preprequisite for X11, because it needs $DISPLAY.) Frees 3 bytes.")
parser.add_argument('-funsafe-dynamic', default=False, action='store_true', \
help="Don't end the ELF Dyn table with a DT_NULL entry. This might "+\
"cause ld.so to interpret the entire binary as the Dyn table, "+\
"so only enable this if you're sure this won't break things!")
parser.add_argument('--nasm', default=os.getenv('NASM') or shutil.which('nasm'), \
help="which nasm binary to use")
parser.add_argument('--cc', default=os.getenv('CC') or shutil.which('cc'), \
help="which cc binary to use (MUST BE GCC!)")
parser.add_argument('--scanelf', default=os.getenv('SCANELF') or shutil.which('scanelf'), \
help="which scanelf binary to use")
parser.add_argument('--readelf', default=os.getenv('READELF') or shutil.which('readelf'), \
help="which readelf binary to use")
parser.add_argument('--cflags', default=[], metavar='CFLAGS', action='append',
help="Flags to pass to the C compiler for the relinking step")
parser.add_argument('--asflags', default=[], metavar='ASFLAGS', action='append',
help="Flags to pass to the assembler when creating the ELF header and runtime startup code")
parser.add_argument('--ldflags', default=[], metavar='LDFLAGS', action='append',
help="Flags to pass to the linker for the final linking step")
parser.add_argument('--smolrt', default=os.getcwd()+"/rt",
help="Directory containing the smol runtime sources")
parser.add_argument('--smolld', default=os.getcwd()+"/ld",
help="Directory containing the smol linker scripts")
parser.add_argument('--verbose', default=False, action='store_true', \
help="Be verbose about what happens and which subcommands are invoked")
parser.add_argument('--keeptmp', default=False, action='store_true', \
help="Keep temp files (only useful for debugging)")
parser.add_argument('input', nargs='+', help="input object file")
parser.add_argument('output', type=str, help="output binary")
args = parser.parse_args()
if args.hash16:
args.fuse_dnload_loader = True
if args.fskip_zero_value: args.asflags.insert(0, "-DSKIP_ZERO_VALUE")
if args.fuse_nx: args.asflags.insert(0, "-DUSE_NX")
if args.fskip_entries: args.asflags.insert(0, "-DSKIP_ENTRIES")
if args.funsafe_dynamic: args.asflags.insert(0, "-DUNSAFE_DYNAMIC")
if args.fno_start_arg: args.asflags.insert(0, "-DNO_START_ARG")
if args.fuse_dl_fini: args.asflags.insert(0, "-DUSE_DL_FINI")
if args.fuse_dt_debug: args.asflags.insert(0, "-DUSE_DT_DEBUG")
if args.fuse_dnload_loader: args.asflags.insert(0, "-DUSE_DNLOAD_LOADER")
if args.fuse_interp: args.asflags.insert(0, "-DUSE_INTERP")
if args.falign_stack: args.asflags.insert(0, "-DALIGN_STACK")
for x in ['nasm','cc','scanelf','readelf']:
val = args.__dict__[x]
if val is None or not os.path.isfile(val):
error("'" + x + "' binary" + (" " if val is None
else " ('" + val + "')") + " not found")
arch = args.target.tolower() if len(args.target) != 0 else decide_arch(args.input)
if arch not in archmagic:
error("Unknown/unsupported architecture '" + str(arch) + "'")
if args.verbose: eprintf("arch: %s" % arch)
objinput = None
objinputistemp = False
tmp_asm_file = tempfile.mkstemp(prefix='smoltab',suffix='.asm',text=True)
tmp_asm_fd = tmp_asm_file[0]
tmp_asm_file = tmp_asm_file[1]
tmp_elf_file = tempfile.mkstemp(prefix='smolout',suffix='.o')
os.close(tmp_elf_file[0])
tmp_elf_file = tmp_elf_file[1]
try:
# if >1 input OR input is LTO object:
if len(args.input) > 1 or has_lto_object(args.readelf, args.input):
fd, objinput = tempfile.mkstemp(prefix='smolin',suffix='.o')
os.close(fd)
cc_relink_objs(args.verbose, args.cc, arch, args.input, objinput, args.cflags)
else: objinput = args.input[0]
# generate smol hashtab
cc_paths = get_cc_paths(args.cc)
syms = get_needed_syms(args.readelf, objinput)
spaths = args.libdir + cc_paths['libraries']
libraries = cc_paths['libraries']
libs = list(find_libs(spaths, args.library))
if args.verbose: eprintf("libs = " + str(libs))
symbols = {}
for symbol, reloc in syms:
library = find_symbol(args.scanelf, libs, args.library, symbol)
if not library:
error("could not find symbol: {}".format(symbol))
symbols.setdefault(library, [])
symbols[library].append((symbol, reloc))