LibC+LibELF: Implement support for the dl_iterate_phdr helper

This helper is used by libgcc_s to figure out where the .eh_frame sections
are located for all loaded shared objects.

Kernel/CoreDump.cpp

@@ -37,8 +37,8 @@
 #include <Kernel/RTC.h>
 #include <Kernel/SpinLock.h>
 #include <Kernel/VM/ProcessPagingScope.h>
+#include <LibC/elf.h>
 #include <LibELF/CoreDump.h>
-#include <LibELF/exec_elf.h>
 
 namespace Kernel {
 

Kernel/CoreDump.h

@@ -31,7 +31,6 @@
 #include <AK/NonnullRefPtr.h>
 #include <AK/OwnPtr.h>
 #include <Kernel/Forward.h>
-#include <LibELF/exec_elf.h>
 
 namespace Kernel {
 

Kernel/Process.h

@@ -49,8 +49,8 @@
 #include <Kernel/VM/AllocationStrategy.h>
 #include <Kernel/VM/RangeAllocator.h>
 #include <Kernel/VM/Space.h>
+#include <LibC/elf.h>
 #include <LibC/signal_numbers.h>
-#include <LibELF/exec_elf.h>
 
 namespace Kernel {
 

Meta/check-debug-flags.sh

@@ -8,6 +8,11 @@ cd "${script_path}/.."
 MISSING_FLAGS=n
 
 while IFS= read -r FLAG; do
+    # Ignore ELF_DEBUG because it's not a debug flag.
+    if [ "$FLAG" = "ELF_DEBUG" ]; then
+        continue
+    fi
+
     # We simply search whether the CMakeLists.txt *ever* sets the flag.
     # There are (basically) no false positives, but there might be false negatives,
     # for example we intentionally don't check for commented-out lines here.

Userland/DynamicLoader/main.cpp

@@ -66,7 +66,7 @@ static void perform_self_relocations(auxv_t* auxvp)
     if (!dynamic_section_addr)
         exit(1);
 
-    auto dynamic_object = ELF::DynamicObject::create((VirtualAddress(base_address)), (VirtualAddress(dynamic_section_addr)));
+    auto dynamic_object = ELF::DynamicObject::create({}, (VirtualAddress(base_address)), (VirtualAddress(dynamic_section_addr)));
 
     dynamic_object->relocation_section().for_each_relocation([base_address](auto& reloc) {
         if (reloc.type() != R_386_RELATIVE)

Userland/Libraries/LibC/CMakeLists.txt

@@ -13,6 +13,7 @@ set(LIBC_SOURCES
     ioctl.cpp
     libcinit.cpp
     libgen.cpp
+    link.cpp
     locale.cpp
     malloc.cpp
     mman.cpp

Userland/Libraries/LibELF/exec_elf.h → Userland/Libraries/LibC/elf.h

@@ -30,10 +30,13 @@
  * formerly known as "elf_abi.h".
  */
 
-#ifndef _SYS_EXEC_ELF_H_
-#define _SYS_EXEC_ELF_H_
+#pragma once
 
-#include <AK/Types.h>
+#ifndef KERNEL
+#    include <sys/types.h>
+#else
+#    include <AK/Types.h>
+#endif
 
 typedef uint8_t Elf_Byte;
 
@@ -788,5 +791,3 @@ struct elf_args {
 #define R_386_RELATIVE 8   /* Base address + Addned */
 #define R_386_TLS_TPOFF 14 /* Negative offset into the static TLS storage */
 #define R_386_TLS_TPOFF32 37
-
-#endif /* _SYS_EXEC_ELF_H_ */

Userland/Libraries/LibC/link.cpp

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2021, Gunnar Beutner <gunnar@beutner.name>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <assert.h>
+#include <link.h>
+
+extern "C" {
+
+using DlIteratePhdrCallbackFunction = int (*)(struct dl_phdr_info*, size_t, void*);
+using DlIteratePhdrFunction = int (*)(DlIteratePhdrCallbackFunction, void*);
+
+DlIteratePhdrFunction __dl_iterate_phdr;
+
+int dl_iterate_phdr(int (*callback)(struct dl_phdr_info* info, size_t size, void* data), void* data)
+{
+    return __dl_iterate_phdr(callback, data);
+}
+}

Userland/Libraries/LibC/link.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2021, Gunnar Beutner <gunnar@beutner.name>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#ifndef __serenity__
+#    include <LibC/elf.h>
+#else
+#    include <elf.h>
+#endif
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#define ElfW(type) Elf32_##type
+
+struct dl_phdr_info {
+    Elf32_Addr dlpi_addr;
+    const char* dlpi_name;
+    const Elf32_Phdr* dlpi_phdr;
+    Elf32_Half dlpi_phnum;
+};
+
+int dl_iterate_phdr(int (*callback)(struct dl_phdr_info* info, size_t size, void* data), void* data);
+
+__END_DECLS

Userland/Libraries/LibELF/DynamicLinker.cpp

@@ -32,6 +32,7 @@
 #include <AK/LexicalPath.h>
 #include <AK/NonnullRefPtrVector.h>
 #include <AK/ScopeGuard.h>
+#include <LibC/link.h>
 #include <LibC/mman.h>
 #include <LibC/unistd.h>
 #include <LibELF/AuxiliaryVector.h>
@@ -52,6 +53,8 @@ Vector<NonnullRefPtr<ELF::DynamicObject>> g_global_objects;
 
 using EntryPointFunction = int (*)(int, char**, char**);
 using LibCExitFunction = void (*)(int);
+using DlIteratePhdrCallbackFunction = int (*)(struct dl_phdr_info*, size_t, void*);
+using DlIteratePhdrFunction = int (*)(DlIteratePhdrCallbackFunction, void*);
 
 size_t g_current_tls_offset = 0;
 size_t g_total_tls_size = 0;
@@ -162,6 +165,24 @@ static void allocate_tls()
     g_total_tls_size = total_tls_size;
 }
 
+static int __dl_iterate_phdr(DlIteratePhdrCallbackFunction callback, void* data)
+{
+    for (auto& object : g_global_objects) {
+        auto info = dl_phdr_info {
+            .dlpi_addr = (ElfW(Addr))object->base_address().as_ptr(),
+            .dlpi_name = object->filename().characters(),
+            .dlpi_phdr = object->program_headers(),
+            .dlpi_phnum = object->program_header_count()
+        };
+
+        auto res = callback(&info, sizeof(info), data);
+        if (res != 0)
+            return res;
+    }
+
+    return 0;
+}
+
 static void initialize_libc(DynamicObject& libc)
 {
     // Traditionally, `_start` of the main program initializes libc.
@@ -181,6 +202,10 @@ static void initialize_libc(DynamicObject& libc)
     VERIFY(res.has_value());
     g_libc_exit = (LibCExitFunction)res.value().address.as_ptr();
 
+    res = libc.lookup_symbol("__dl_iterate_phdr"sv);
+    VERIFY(res.has_value());
+    *((DlIteratePhdrFunction*)res.value().address.as_ptr()) = __dl_iterate_phdr;
+
     res = libc.lookup_symbol("__libc_init"sv);
     VERIFY(res.has_value());
     typedef void libc_init_func();

Userland/Libraries/LibELF/DynamicLinker.h

@@ -27,7 +27,9 @@
 #pragma once
 
 #include <AK/Result.h>
+#include <AK/String.h>
 #include <AK/Vector.h>
+#include <LibC/link.h>
 #include <LibELF/DynamicObject.h>
 
 namespace ELF {

Userland/Libraries/LibELF/DynamicLoader.cpp

@@ -113,7 +113,7 @@ const DynamicObject& DynamicLoader::dynamic_object() const
         });
         VERIFY(!dynamic_section_address.is_null());
 
-        m_cached_dynamic_object = ELF::DynamicObject::create(VirtualAddress(m_elf_image.base_address()), dynamic_section_address);
+        m_cached_dynamic_object = ELF::DynamicObject::create(m_filename, VirtualAddress(m_elf_image.base_address()), dynamic_section_address);
     }
     return *m_cached_dynamic_object;
 }
@@ -170,7 +170,7 @@ RefPtr<DynamicObject> DynamicLoader::map()
 
     VERIFY(!m_base_address.is_null());
 
-    m_dynamic_object = DynamicObject::create(m_base_address, m_dynamic_section_address);
+    m_dynamic_object = DynamicObject::create(m_filename, m_base_address, m_dynamic_section_address);
     m_dynamic_object->set_tls_offset(m_tls_offset);
     m_dynamic_object->set_tls_size(m_tls_size);
 

Userland/Libraries/LibELF/DynamicLoader.h

@@ -31,9 +31,9 @@
 #include <AK/OwnPtr.h>
 #include <AK/RefCounted.h>
 #include <AK/String.h>
+#include <LibC/elf.h>
 #include <LibELF/DynamicObject.h>
 #include <LibELF/Image.h>
-#include <LibELF/exec_elf.h>
 #include <sys/mman.h>
 
 namespace ELF {

Userland/Libraries/LibELF/DynamicObject.cpp

@@ -28,18 +28,19 @@
 #include <AK/Debug.h>
 #include <AK/String.h>
 #include <AK/StringBuilder.h>
+#include <LibC/elf.h>
 #include <LibELF/DynamicLoader.h>
 #include <LibELF/DynamicObject.h>
 #include <LibELF/Hashes.h>
-#include <LibELF/exec_elf.h>
 #include <string.h>
 
 namespace ELF {
 
 static const char* name_for_dtag(Elf32_Sword d_tag);
 
-DynamicObject::DynamicObject(VirtualAddress base_address, VirtualAddress dynamic_section_address)
-    : m_base_address(base_address)
+DynamicObject::DynamicObject(const String& filename, VirtualAddress base_address, VirtualAddress dynamic_section_address)
+    : m_filename(filename)
+    , m_base_address(base_address)
     , m_dynamic_address(dynamic_section_address)
 {
     auto* header = (Elf32_Ehdr*)base_address.as_ptr();
@@ -255,6 +256,18 @@ DynamicObject::RelocationSection DynamicObject::plt_relocation_section() const
     return RelocationSection(Section(*this, m_plt_relocation_offset_location, m_size_of_plt_relocation_entry_list, m_size_of_relocation_entry, "DT_JMPREL"sv));
 }
 
+Elf32_Half DynamicObject::program_header_count() const
+{
+    auto* header = (const Elf32_Ehdr*)m_base_address.as_ptr();
+    return header->e_phnum;
+}
+
+const Elf32_Phdr* DynamicObject::program_headers() const
+{
+    auto* header = (const Elf32_Ehdr*)m_base_address.as_ptr();
+    return (const Elf32_Phdr*)(m_base_address.as_ptr() + header->e_phoff);
+}
+
 auto DynamicObject::HashSection::lookup_sysv_symbol(const StringView& name, u32 hash_value) const -> Optional<Symbol>
 {
     u32* hash_table_begin = (u32*)address().as_ptr();
@@ -447,9 +460,9 @@ auto DynamicObject::lookup_symbol(const StringView& name, u32 gnu_hash, u32 sysv
     return SymbolLookupResult { symbol.value(), symbol.address(), symbol.bind(), this };
 }
 
-NonnullRefPtr<DynamicObject> DynamicObject::create(VirtualAddress base_address, VirtualAddress dynamic_section_address)
+NonnullRefPtr<DynamicObject> DynamicObject::create(const String& filename, VirtualAddress base_address, VirtualAddress dynamic_section_address)
 {
-    return adopt(*new DynamicObject(base_address, dynamic_section_address));
+    return adopt(*new DynamicObject(filename, base_address, dynamic_section_address));
 }
 
 // offset is in PLT relocation table

Userland/Libraries/LibELF/DynamicObject.h

@@ -29,14 +29,15 @@
 
 #include <AK/Assertions.h>
 #include <AK/RefCounted.h>
+#include <AK/String.h>
 #include <Kernel/VirtualAddress.h>
-#include <LibELF/exec_elf.h>
+#include <LibC/elf.h>
 
 namespace ELF {
 
 class DynamicObject : public RefCounted<DynamicObject> {
 public:
-    static NonnullRefPtr<DynamicObject> create(VirtualAddress base_address, VirtualAddress dynamic_section_address);
+    static NonnullRefPtr<DynamicObject> create(const String& filename, VirtualAddress base_address, VirtualAddress dynamic_section_address);
 
     ~DynamicObject();
     void dump() const;
@@ -238,6 +239,8 @@ public:
     VirtualAddress plt_got_base_address() const { return m_base_address.offset(m_procedure_linkage_table_offset.value()); }
     VirtualAddress base_address() const { return m_base_address; }
 
+    const String& filename() const { return m_filename; }
+
     StringView rpath() const { return m_has_rpath ? symbol_string_table_string(m_rpath_index) : StringView {}; }
     StringView runpath() const { return m_has_runpath ? symbol_string_table_string(m_runpath_index) : StringView {}; }
     StringView soname() const { return m_has_soname ? symbol_string_table_string(m_soname_index) : StringView {}; }
@@ -247,6 +250,9 @@ public:
     void set_tls_offset(FlatPtr offset) { m_tls_offset = offset; }
     void set_tls_size(FlatPtr size) { m_tls_size = size; }
 
+    Elf32_Half program_header_count() const;
+    const Elf32_Phdr* program_headers() const;
+
     template<typename F>
     void for_each_needed_library(F) const;
 
@@ -275,12 +281,14 @@ public:
     bool elf_is_dynamic() const { return m_is_elf_dynamic; }
 
 private:
-    explicit DynamicObject(VirtualAddress base_address, VirtualAddress dynamic_section_address);
+    explicit DynamicObject(const String& filename, VirtualAddress base_address, VirtualAddress dynamic_section_address);
 
     StringView symbol_string_table_string(Elf32_Word) const;
     const char* raw_symbol_string_table_string(Elf32_Word) const;
     void parse();
 
+    String m_filename;
+
     VirtualAddress m_base_address;
     VirtualAddress m_dynamic_address;
     VirtualAddress m_elf_base_address;

Userland/Libraries/LibELF/Image.h

@@ -29,7 +29,7 @@
 #include <AK/String.h>
 #include <AK/Vector.h>
 #include <Kernel/VirtualAddress.h>
-#include <LibELF/exec_elf.h>
+#include <LibC/elf.h>
 
 namespace ELF {
 

Userland/Libraries/LibELF/Validation.cpp

@@ -28,8 +28,8 @@
 #include <AK/Assertions.h>
 #include <AK/Checked.h>
 #include <AK/String.h>
+#include <LibC/elf.h>
 #include <LibELF/Validation.h>
-#include <LibELF/exec_elf.h>
 
 namespace ELF {
 

Userland/Libraries/LibELF/Validation.h

@@ -27,7 +27,7 @@
 #pragma once
 
 #include <AK/String.h>
-#include <LibELF/exec_elf.h>
+#include <LibC/elf.h>
 
 namespace ELF {
 

Userland/Tests/Kernel/elf-execve-mmap-race.cpp

@@ -24,7 +24,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <LibELF/exec_elf.h>
+#include <AK/Types.h>
+#include <elf.h>
 #include <fcntl.h>
 #include <pthread.h>
 #include <stdio.h>

Userland/Tests/Kernel/elf-symbolication-kernel-read-exploit.cpp

@@ -24,7 +24,8 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <LibELF/exec_elf.h>
+#include <AK/Types.h>
+#include <elf.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <string.h>