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smol
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resolve IFUNCs correctly

This commit is contained in:
PoroCYon 2020-08-22 03:41:25 +02:00
parent 494d32638a
commit daf76fec8e
8 changed files with 104 additions and 18 deletions
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2
.gitignore vendored
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@ -1,3 +1,5 @@
/bin
/obj
__pycache__
smol-*-*-*/
*.tar.xz

13
Makefile
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@ -4,6 +4,7 @@ SRCDIR := rt
TESTDIR:= test
NASM ?= nasm
OBJCOPY ?= objcopy
BITS ?= $(shell getconf LONG_BIT)
@ -35,12 +36,12 @@ else
CFLAGS += -march=nocona
endif
LIBS = $(filter-out -pthread,$(shell pkg-config --libs sdl2)) -lX11 -lc #-lGL
LIBS = $(filter-out -pthread,$(shell pkg-config --libs sdl2)) -lX11 -lm -lc #-lGL
PWD ?= .
SMOLFLAGS = --smolrt "$(PWD)/rt" --smolld "$(PWD)/ld" \
-falign-stack -fuse-interp \
-falign-stack -fuse-interp -fifunc-support \
--verbose #--keeptmp
# -fuse-dnload-loader -fskip-zero-value -fuse-nx -fskip-entries -fuse-dt-debug
# -fuse-dl-fini -fno-start-arg -funsafe-dynamic
@ -67,11 +68,13 @@ $(OBJDIR)/%.o: $(SRCDIR)/%.c $(OBJDIR)/
$(OBJDIR)/%.o: $(TESTDIR)/%.c $(OBJDIR)/
$(CC) $(CFLAGS) -c "$<" -o "$@"
$(BINDIR)/%: $(OBJDIR)/%.o $(BINDIR)/
$(PYTHON3) ./smold.py $(SMOLFLAGS) $(LIBS) "$<" "$@"
$(BINDIR)/%.dbg $(BINDIR)/%: $(OBJDIR)/%.o $(BINDIR)/
$(PYTHON3) ./smold.py --debugout $(SMOLFLAGS) --ldflags=-Wl,-Map=$(BINDIR)/$*.map $(LIBS) "$<" "$@.dbg"
$(PYTHON3) ./smold.py $(SMOLFLAGS) --ldflags=-Wl,-Map=$(BINDIR)/$*.map $(LIBS) "$<" "$@"
$(PYTHON3) ./smoltrunc.py "$@" "$(OBJDIR)/$(notdir $@)" && mv "$(OBJDIR)/$(notdir $@)" "$@" && chmod +x "$@"
$(BINDIR)/%-crt: $(OBJDIR)/%.lto.o $(OBJDIR)/crt1.lto.o $(BINDIR)/
$(BINDIR)/%-crt.dbg $(BINDIR)/%-crt: $(OBJDIR)/%.lto.o $(OBJDIR)/crt1.lto.o $(BINDIR)/
$(PYTHON3) ./smold.py --debugout $(SMOLFLAGS) --ldflags=-Wl,-Map=$(BINDIR)/$*-crt.map $(LIBS) "$<" $(OBJDIR)/crt1.lto.o "$@.dbg"
$(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 "$@"

23
ld/link.ld
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@ -1,10 +1,19 @@
OUTPUT_FORMAT(binary)
OUTPUT_FORMAT("elf64-x86-64", "elf64-x86-64", "elf64-x86-64")
OUTPUT_ARCH(i386:x86-64)
ENTRY(_smol_start)
SEARCH_DIR("/usr/x86_64-pc-linux-gnu/lib64"); SEARCH_DIR("/usr/lib"); SEARCH_DIR("/usr/local/lib"); SEARCH_DIR("/usr/x86_64-pc-linux-gnu/lib");
/*OUTPUT_FORMAT(binary)*/
PHDRS {
rodttxt PT_LOAD FLAGS(5); /* r-x */
rwdt PT_LOAD FLAGS(6); /* rw- */
}
SECTIONS {
. = 0x10000;
_smol_origin = .;
.header : { KEEP(*(.header)) }
.header : { KEEP(*(.header)) } :rodttxt
_smol_text_start = .;
_smol_text_off = _smol_text_start - _smol_origin;
@ -15,7 +24,7 @@ SECTIONS {
KEEP(*(.text.startup.smol))
KEEP(*(.text.startup._start))
*(.text .text.*)
}
} :rodttxt
_smol_text_end = .;
_smol_text_size = _smol_text_end - _smol_text_start;
@ -26,10 +35,10 @@ SECTIONS {
.data : {
KEEP(*(.data.smolgot))
*(.data .data.* .tdata .tdata.*)
}
} :rwdt
.dynamic : { *(.dynamic) } :all :dyn
.dynstuff : { *(.symtab .strtab .shstrtab .rel.text .got.plt .gnu.linkonce.* .plt .plt.got .interp) } :all
.dynamic : { *(.dynamic) } :rodttxt :dyn
.dynstuff : { *(.symtab .strtab .shstrtab .rel.text .got.plt .gnu.linkonce.* .plt .plt.got .interp) } :rodttxt
_smol_data_end = .;
_smol_data_size = _smol_data_end - _smol_data_start;
@ -39,7 +48,7 @@ SECTIONS {
_smol_bss_off = _smol_bss_start - _smol_origin;
.bss : {
*(.bss .bss.* .tbss .tbss.* .sbss .sbss.*)
}
} :rwdt
_smol_bss_end = .;
_smol_bss_size = _smol_bss_end - _smol_bss_start;

7
rt/elf.inc
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@ -34,17 +34,22 @@
%define DT_SYMTAB ( 6)
%define DT_DEBUG (21)
%define ST_NAME_OFF ( 0)
%define ST_NAME_OFF ( 0)
%define ST_INFO__STT_MASK (15)
%define STT_GNU_IFUNC (10)
; ,---- not 16? ; what's this comment??!
; v
%if __BITS__ == 32
%define D_UN_PTR_OFF ( 4)
%define ST_VALUE_OFF ( 4)
%define ST_INFO_OFF (12)
%define SYMTAB_SIZE (16)
%define ELF_DYN_SZ ( 8)
%else
%define D_UN_PTR_OFF ( 8)
%define ST_VALUE_OFF ( 8)
%define ST_INFO_OFF ( 4)
%define SYMTAB_SIZE (24)
%define ELF_DYN_SZ (16)
%endif

55
rt/loader64.asm
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@ -127,16 +127,51 @@ _smol_start:
jmp short .next_link
.hasheq:
%ifdef IFUNC_SUPPORT
mov cl , [rdx + ST_INFO_OFF]
%endif
mov rax, [rdx + ST_VALUE_OFF]
%ifdef SKIP_ZERO_VALUE
or rax, rax
jz short .next_link
%endif
add rax, [r12 + L_ADDR_OFF]
%ifdef IFUNC_SUPPORT
and cl, ST_INFO__STT_MASK
cmp cl, STT_GNU_IFUNC
je .ifunc
.no_ifunc:
%endif
stosq
cmp word [rdi], 0
jne short .next_hash
%ifdef IFUNC_SUPPORT
jmp short .break_loop
.ifunc:
;;int3 ; in this call, we lose rax rcx rdx rsi rdi r8 r9 r10 r11
; we only need persistence for rdi and r11 tho
;push rcx
;push rdx
;push rsi
push rdi
;push r8
;push r9
;push r10
push r11
call rax
pop r11
;pop r10
;pop r9
;pop r8
pop rdi
;pop rsi
;pop rdx
;pop rcx
jmp short .no_ifunc
.break_loop:
%endif
; if USE_DNLOAD_LOADER
%else
push _smol_start
@ -219,6 +254,12 @@ repne scasd ; technically, scasq should be used, but meh. this is 1 byte smaller
mov rax, [rax + D_UN_PTR_OFF]
; ElfW(Addr) symoff(rax) = symtab[bucket].st_value
lea rdx, [rcx + rcx * 2]
%ifdef IFUNC_SUPPORT
; large opcode, but, ~almost the same as the next one, so,
; should compress well
mov cl, [rax + rdx * 8 + ST_INFO_OFF] ; TODO: actually mov cl, ...
%endif
mov rax, [rax + rdx * 8 + ST_VALUE_OFF]
%ifdef SKIP_ZERO_VALUE
or rax, rax ; zero value => weak symbol or sth
@ -227,6 +268,20 @@ repne scasd ; technically, scasq should be used, but meh. this is 1 byte smaller
; void* finaladdr(rax) = symoff + entry->l_addr
add rax, [r12 + L_ADDR_OFF]
%ifdef IFUNC_SUPPORT
; is this an ifunc?
and cl, ST_INFO__STT_MASK
cmp cl, STT_GNU_IFUNC
jne .no_ifunc
; if so: call the resolver
push rdi
push r11
call rax
pop r11
pop rdi
.no_ifunc:
%endif
; *phash = finaladdr
stosq
cmp word [rdi], 0

10
smol/cnl.py
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@ -28,12 +28,14 @@ def nasm_assemble_elfhdr(verbose, nasm_bin, arch, rtdir, intbl, output, asflags)
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):
def ld_link_final(verbose, cc_bin, arch, lddir, inobjs, output, ldflags, debug):
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
args = [cc_bin, archflag, '-T', lddir+'/link.ld', '-no-pie']
if not debug:
args.append('-Wl,--oformat=binary')
#args = [*args, '-T', lddir+'/link.ld', '-Wl,--oformat=binary']
args += ['-nostartfiles', '-nostdlib', '-o', output, *inobjs, *ldflags]
if verbose: eprintf("ld: %s" % repr(args))
subprocess.check_call(args, stdout=subprocess.DEVNULL)

10
smold.py
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@ -74,6 +74,9 @@ def main():
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('-fifunc-support', default=False, action='store_true', \
help="Support linking to IFUNCs. Probably needed on x86_64, but costs "+\
"~16 bytes. Ignored on platforms other than x86_64 or aarch64.")
parser.add_argument('--nasm', default=os.getenv('NASM') or shutil.which('nasm'), \
help="which nasm binary to use")
@ -99,6 +102,10 @@ def main():
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('--debugout', default=False, action='store_true', \
help="Output an unrunnable debug ELF file with symbol information. "+\
"(Useful for debugging with gdb, cannot be ran due to broken "+\
"relocations.)")
parser.add_argument('input', nargs='+', help="input object file")
parser.add_argument('output', type=str, help="output binary")
@ -118,6 +125,7 @@ def main():
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")
if args.fifunc_support: args.asflags.insert(0, "-DIFUNC_SUPPORT")
for x in ['nasm','cc','scanelf','readelf']:
val = args.__dict__[x]
@ -172,7 +180,7 @@ def main():
# link with LD into the final executable, w/ special linker script
ld_link_final(args.verbose, args.cc, arch, args.smolld, [objinput, tmp_elf_file],
args.output, args.ldflags)
args.output, args.ldflags, args.debugout)
finally:
if not args.keeptmp:
if objinputistemp: os.remove(objinput)

2
test/hello.c
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@ -1,6 +1,7 @@
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
const char *f = "foo";
@ -10,6 +11,7 @@ int main(int argc, char* argv[]) {
printf("argv=%p\n", (void*)argv);
for (int i = 0; i < argc; ++i)
printf("argv[%d](%p)=%s\n", i, (void*)argv[i], argv[i]);
printf("sin(%d)=%f\n", argc, sinf(argc));
exit(42);
}