Merge pull request #6 from rlane/elf3

elf: relocate function calls

test_framework/expand-testcase.py

@@ -60,8 +60,13 @@ def writefile(name, contents):
 
     if 'asm' in data:
         writefile('asm', data['asm'])
-    else:
+    elif code:
         writefile('asm', ubpf.disassembler.disassemble(code))
 
+    if 'pyelf' in data:
+        from test_elf import generate_elf
+        elf = generate_elf(data['pyelf'])
+        writefile('elf', elf)
+
 if __name__ == "__main__":
     main()

test_framework/test_elf.py

@@ -9,6 +9,7 @@
 from elftools.construct import Container
 from elftools.elf.constants import SH_FLAGS
 import testdata
+import ubpf.assembler
 VM = os.path.join(os.path.dirname(os.path.realpath(__file__)), "..", "vm", "test")
 
 def template():
@@ -37,7 +38,7 @@ def add(name, value):
         e_phentsize=0,
         e_phnum=0,
         e_shentsize=64,
-        e_shnum=4,
+        e_shnum=5,
         e_shstrndx=2))
 
     add('first_shdr', Container(
@@ -57,8 +58,8 @@ def add(name, value):
         sh_type='SHT_PROGBITS',
         sh_flags=SH_FLAGS.SHF_ALLOC|SH_FLAGS.SHF_EXECINSTR,
         sh_addr=0,
-        sh_offset=320,
-        sh_size=16,
+        sh_offset=384,
+        sh_size=24,
         sh_link=0,
         sh_info=0,
         sh_addralign=8,
@@ -69,8 +70,8 @@ def add(name, value):
         sh_type='SHT_STRTAB',
         sh_flags=0,
         sh_addr=0,
-        sh_offset=336,
-        sh_size=23,
+        sh_offset=408,
+        sh_size=34,
         sh_link=0,
         sh_info=0,
         sh_addralign=1,
@@ -81,22 +82,62 @@ def add(name, value):
         sh_type='SHT_SYMTAB',
         sh_flags=0,
         sh_addr=0,
-        sh_offset=359,
-        sh_size=0,
-        sh_link=0,
+        sh_offset=442,
+        sh_size=48,
+        sh_link=2,
         sh_info=0,
         sh_addralign=8,
         sh_entsize=24))
 
-    add("text", "\xb7\x00\x00\x00\x2a\x00\x00\x00\x95\x00\x00\x00\x00\x00\x00\x00")
-    add("strtab", "\0.text\0.strtab\0.symtab\0")
-    add("symtab", "")
+    add('rel_shdr', Container(
+        sh_name=23,
+        sh_type='SHT_REL',
+        sh_flags=0,
+        sh_addr=0,
+        sh_offset=490,
+        sh_size=16,
+        sh_link=3,
+        sh_info=1,
+        sh_addralign=8,
+        sh_entsize=16))
+
+    # return sqrti(42*42)
+    asm = """
+mov r1, 1764
+call 0xffffffff
+exit
+"""
+
+    text = ubpf.assembler.assemble(asm)
+
+    add("text", text)
+    add("strtab", "\0.text\0.strtab\0.symtab\0.rel\0sqrti\0")
+    add("first_sym", Container(
+        st_name=0,
+        st_value=0,
+        st_size=0,
+        st_info=Container(bind='STB_WEAK', type='STT_FUNC'),
+        st_other=Container(visibility='STV_DEFAULT'),
+        st_shndx=0))
+    add("sqrti_sym", Container(
+        st_name=28,
+        st_value=0,
+        st_size=0,
+        st_info=Container(bind='STB_WEAK', type='STT_FUNC'),
+        st_other=Container(visibility='STV_DEFAULT'),
+        st_shndx=0))
+    add("sqrti_rel", Container(
+        r_info=(1 << 32) | 2,
+        r_info_sym=0,
+        r_info_type=0,
+        r_offset=8))
 
     return parts
 
 def serialize(parts):
     s = elftools.elf.structs.ELFStructs(elfclass=64)
     tmp = []
+    offset = 0
 
     for name in parts['order']:
         part = parts[name]
@@ -105,10 +146,22 @@ def serialize(parts):
             serializer = s.Elf_Ehdr.build
         elif name.endswith('shdr'):
             serializer = s.Elf_Shdr.build
-        tmp.append(serializer(part))
+        elif name.endswith('rel'):
+            serializer = s.Elf_Rel.build
+        elif name.endswith('sym'):
+            serializer = s.Elf_Sym.build
+        data = serializer(part)
+        tmp.append(data)
+        #sys.stderr.write("Wrote %s size %d at offset %d\n" % (name, len(data), offset))
+        offset += len(data)
 
     return ''.join(tmp)
 
+def generate_elf(pyelf):
+    parts = template()
+    exec(pyelf, parts)
+    return serialize(parts)
+
 def check_datafile(filename):
     """
     """
@@ -120,9 +173,7 @@ def check_datafile(filename):
     if not os.path.exists(VM):
         raise SkipTest("VM not found")
 
-    parts = template()
-    exec(data['pyelf'], parts)
-    elf = serialize(parts)
+    elf = generate_elf(data['pyelf'])
 
     cmd = [VM]
 

tests/elf/bad-rel-offset.data

@@ -0,0 +1,4 @@
+-- pyelf
+sqrti_rel.r_offset = 500
+-- error
+Failed to load code: bad relocation offset

tests/elf/bad-rel-strtab-index.data

@@ -0,0 +1,4 @@
+-- pyelf
+symtab_shdr.sh_link = 30
+-- error
+Failed to load code: bad string table section index

tests/elf/bad-rel-symbol-index.data

@@ -0,0 +1,4 @@
+-- pyelf
+sqrti_rel.r_info = (10 << 32) | 2
+-- error
+Failed to load code: bad symbol index

tests/elf/bad-rel-symbol-name.data

@@ -0,0 +1,4 @@
+-- pyelf
+sqrti_sym.st_name = 100
+-- error
+Failed to load code: bad symbol name

tests/elf/bad-rel-symbol-table-section-index.data

@@ -0,0 +1,4 @@
+-- pyelf
+rel_shdr.sh_link = 30
+-- error
+Failed to load code: bad symbol table section index

tests/elf/bad-rel-type.data

@@ -0,0 +1,4 @@
+-- pyelf
+sqrti_rel.r_info = (1 << 32) | 3
+-- error
+Failed to load code: bad relocation type

tests/elf/bad-section-header-size.data

@@ -1,4 +1,4 @@
 -- pyelf
-ehdr.e_shnum = 1024
+ehdr.e_shentsize = 1024
 -- error
 Failed to load code: bad section header offset or size

tests/elf/rel-sym-not-found.data

@@ -0,0 +1,4 @@
+-- pyelf
+sqrti_sym.st_name += 1
+-- error
+Failed to load code: function 'qrti' not found

tests/elf/too-many-sections.data

@@ -0,0 +1,4 @@
+-- pyelf
+ehdr.e_shnum = 1024
+-- error
+Failed to load code: too many sections

vm/Makefile

@@ -12,15 +12,20 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+DYNASM := ../dynasm
+
+CFLAGS := -Wall -Werror -Iinc -I$(DYNASM) -O2 -g
+LDLIBS := -lm
+
 ifeq ($(COVERAGE),1)
-COVERAGE_CFLAGS := -fprofile-arcs -ftest-coverage
-COVERAGE_LDFLAGS := -fprofile-arcs
+CFLAGS += -fprofile-arcs -ftest-coverage
+LDFLAGS += -fprofile-arcs
 endif
 
-DYNASM := ../dynasm
-
-CFLAGS := -Wall -Werror -Iinc -I$(DYNASM) -O2 -g $(COVERAGE_CFLAGS)
-LDFLAGS := $(COVERAGE_LDFLAGS)
+ifeq ($(ASAN),1)
+CFLAGS += -fsanitize=address
+LDFLAGS += -fsanitize=address
+endif
 
 all: libubpf.a test
 

vm/test.c

@@ -24,6 +24,7 @@
 #include <getopt.h>
 #include <errno.h>
 #include <elf.h>
+#include <math.h>
 #include "ubpf.h"
 
 void ubpf_set_register_offset(int x);
@@ -214,10 +215,17 @@ trash_registers(void)
     );
 }
 
+static uint32_t
+sqrti(uint32_t x)
+{
+    return sqrt(x);
+}
+
 static void
 register_functions(struct ubpf_vm *vm)
 {
     ubpf_register(vm, 0, "gather_bytes", gather_bytes);
     ubpf_register(vm, 1, "memfrob", memfrob);
     ubpf_register(vm, 2, "trash_registers", trash_registers);
+    ubpf_register(vm, 3, "sqrti", sqrti);
 }

vm/ubpf_int.h

@@ -33,5 +33,6 @@ struct ubpf_vm {
 };
 
 char *ubpf_error(const char *fmt, ...);
+unsigned int ubpf_lookup_registered_function(struct ubpf_vm *vm, const char *name);
 
 #endif