options/glibc: implement backtrace

ci/bootstrap.yml

@@ -39,7 +39,7 @@ packages:
         - '--buildtype=debugoptimized'
         - "-Dc_args=['-Wno-error=maybe-uninitialized', '-Wno-unknown-warning-option']"
         - "-Dcpp_args=['-Wno-error=maybe-uninitialized', '-Wno-unknown-warning-option']"
-        - "-Dlibgcc_dependency=false"
+        # - "-Dlibgcc_dependency=false"
         - "-Duse_freestnd_hdrs=enabled"
         - "-Dbuild_tests=true"
         - "-Db_sanitize=undefined"
@@ -51,7 +51,7 @@ packages:
         environ:
           CFLAGS: '-Wno-error=maybe-uninitialized'
           CXXFLAGS: '-Wno-error=maybe-uninitialized'
-          LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
+          # LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
     build:
       - args: ['ninja']
       - args: ['ninja', 'install']
@@ -74,7 +74,7 @@ packages:
         - '--buildtype=debugoptimized'
         - "-Dc_args=['-Wno-error=maybe-uninitialized']"
         - "-Dcpp_args=['-Wno-error=maybe-uninitialized']"
-        - "-Dlibgcc_dependency=false"
+        # - "-Dlibgcc_dependency=false"
         - "-Duse_freestnd_hdrs=enabled"
         - "-Dbuild_tests=true"
         - "-Db_sanitize=undefined"
@@ -83,8 +83,8 @@ packages:
         - '-Dlinux_kernel_headers=@BUILD_ROOT@/packages/linux-headers/usr/include'
         - "--cross-file=@THIS_SOURCE_DIR@/ci/linux-@OPTION:arch@-@OPTION:compiler@.cross-file"
         - '@THIS_SOURCE_DIR@'
-        environ:
-          LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
+        # environ:
+        #   LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
     build:
       - args: ['ninja']
       - args: ['ninja', 'install']
@@ -106,7 +106,7 @@ packages:
         - '--buildtype=debugoptimized'
         - "-Dc_args=['-Wno-error=maybe-uninitialized']"
         - "-Dcpp_args=['-Wno-error=maybe-uninitialized']"
-        - "-Dlibgcc_dependency=false"
+        # - "-Dlibgcc_dependency=false"
         - "-Duse_freestnd_hdrs=enabled"
         - "-Dbuild_tests=true"
         - "-Db_sanitize=undefined"
@@ -115,8 +115,8 @@ packages:
         - '-Dlinux_kernel_headers=@BUILD_ROOT@/packages/linux-headers/usr/include'
         - "--cross-file=@THIS_SOURCE_DIR@/ci/linux-@OPTION:arch@-@OPTION:compiler@.cross-file"
         - '@THIS_SOURCE_DIR@'
-        environ:
-          LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
+        # environ:
+        #   LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
     build:
       - args: ['ninja']
       - args: ['ninja', 'install']
@@ -139,7 +139,7 @@ packages:
         - '--buildtype=debugoptimized'
         - "-Dc_args=['-Wno-error=maybe-uninitialized']"
         - "-Dcpp_args=['-Wno-error=maybe-uninitialized']"
-        - "-Dlibgcc_dependency=false"
+        # - "-Dlibgcc_dependency=false"
         - "-Duse_freestnd_hdrs=enabled"
         - "-Dbuild_tests=true"
         - "-Db_sanitize=undefined"
@@ -152,8 +152,8 @@ packages:
         - '-Dlinux_kernel_headers=@BUILD_ROOT@/packages/linux-headers/usr/include'
         - "--cross-file=@THIS_SOURCE_DIR@/ci/linux-@OPTION:arch@-@OPTION:compiler@.cross-file"
         - '@THIS_SOURCE_DIR@'
-        environ:
-          LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
+        # environ:
+        #   LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
     build:
       - args: ['ninja']
       - args: ['ninja', 'install']
@@ -176,16 +176,16 @@ packages:
         - '--buildtype=debugoptimized'
         - "-Dc_args=['-Wno-error=maybe-uninitialized']"
         - "-Dcpp_args=['-Wno-error=maybe-uninitialized']"
-        - "-Dlibgcc_dependency=false"
+        # - "-Dlibgcc_dependency=false"
         - "-Duse_freestnd_hdrs=enabled"
         - "-Db_sanitize=undefined"
         - "-Dwerror=true"
         - "-Dheaders_only=true"
         - '-Dlinux_kernel_headers=@BUILD_ROOT@/packages/linux-headers/usr/include'
         - "--cross-file=@THIS_SOURCE_DIR@/ci/linux-@OPTION:arch@-@OPTION:compiler@.cross-file"
         - '@THIS_SOURCE_DIR@'
-        environ:
-          LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
+        # environ:
+        #   LDFLAGS: '-Wl,/tmp/libgcc-@OPTION:arch@.a'
     build:
       - args: ['ninja']
       - args: ['ninja', 'install']

meson.build

@@ -452,6 +452,7 @@ rtlib_deps = []
 
 if not headers_only
 	if libgcc_dependency
+		libgcc_eh = meson.get_compiler('c').find_library('gcc_eh', required: false)
 		libgcc = meson.get_compiler('c').find_library('gcc', required: false)
 
 		compiler_rt_name = 'libclang_rt.builtins-' + host_machine.cpu_family()
@@ -462,6 +463,10 @@ if not headers_only
 			compiler_rt = meson.get_compiler('c').find_library(compiler_rt_name, required: false)
 		endif
 
+		if libgcc_eh.found()
+			libc_deps += libgcc_eh
+		endif
+
 		if libgcc.found()
 			rtlib_deps += libgcc
 		elif compiler_rt.found()

options/elf/include/elf.h

@@ -482,7 +482,9 @@ enum {
 	DT_VERDEF = 0x6ffffffc,
 	DT_VERDEFNUM = 0x6ffffffd,
 	DT_VERNEED = 0x6ffffffe,
-	DT_VERNEEDNUM = 0x6fffffff
+	DT_VERNEEDNUM = 0x6fffffff,
+	DT_LOPROC = 0x70000000,
+	DT_HIPROC = 0x7fffffff
 };
 
 enum {

options/glibc/generic/execinfo.cpp

@@ -1,19 +1,77 @@
+#include <dlfcn.h>
 #include <execinfo.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <unwind.h>
 
 #include <bits/ensure.h>
 #include <mlibc/debug.hpp>
 
-int backtrace(void **, int) {
-	mlibc::infoLogger() << "mlibc: backtrace() is a stub!" << frg::endlog;
-	return 0;
+namespace {
+
+struct UnwindState {
+	void **frames;
+	int count;
+	int current_frame = 0;
+};
+
+_Unwind_Reason_Code trace(_Unwind_Context *context, void *arg) {
+	uintptr_t ip = _Unwind_GetIP(context);
+
+	if (ip) {
+#if defined(__x86_64__) || defined(__i386__)
+		ip--;
+#elif defined(__aarch64__) || defined(__loongarch64)
+		ip -= 4;
+#elif defined(__riscv) || defined(__m68k__)
+		ip -= 2;
+#else
+#warning "Missing support for architecture"
+		ip--;
+#endif
+	}
+
+	UnwindState *state = static_cast<UnwindState *>(arg);
+	state->frames[state->current_frame++] = reinterpret_cast<void *>(ip);
+	return (state->current_frame >= state->count) ? _URC_END_OF_STACK : _URC_NO_REASON;
+}
+
+} // namespace
+
+int backtrace(void **buffer, int size) {
+	if (size <= 0)
+		return 0;
+
+	UnwindState state{buffer, size};
+	_Unwind_Backtrace(trace, &state);
+	return state.current_frame;
 }
 
 char **backtrace_symbols(void *const *, int) {
 	__ensure(!"Not implemented");
 	__builtin_unreachable();
 }
 
-void backtrace_symbols_fd(void *const *, int, int) {
-	__ensure(!"Not implemented");
-	__builtin_unreachable();
+void backtrace_symbols_fd(void *const *buffer, int size, int fd) {
+	if (size <= 0 || fd < 0)
+		return;
+
+	for (int frame_num = 0; frame_num < size; frame_num++) {
+		Dl_info info;
+		if (dladdr(buffer[frame_num], &info) != 0) {
+			if (info.dli_fname != nullptr)
+				write(fd, info.dli_fname, strlen(info.dli_fname));
+
+			if (info.dli_sname != nullptr)
+				dprintf(fd, "(%s+0x%" PRIxPTR ") ", info.dli_sname,
+					reinterpret_cast<uintptr_t>(buffer[frame_num]) - reinterpret_cast<uintptr_t>(info.dli_saddr));
+			else if(info.dli_saddr)
+				dprintf(fd, "(+%p) ", info.dli_saddr);
+			else
+				dprintf(fd, "() ");
+		}
+
+		dprintf(fd, "[%p]\n", buffer[frame_num]);
+	}
 }

options/internal/include/mlibc-asm/helpers.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#if !defined(__ASSEMBLER__)
+#error "This file can only be used by assembly files."
+#endif
+
+#define PROC_START(name) \
+	.global name; \
+	.type name, @function; \
+	.cfi_startproc; \
+	name:
+
+#define PROC_END(name) \
+	.cfi_endproc; \
+	.size name, . - name

options/posix/generic/dlfcn.cpp

@@ -18,6 +18,7 @@ extern "C" void *__dlapi_open(const char *, int, void *);
 extern "C" void *__dlapi_resolve(void *, const char *, void *, const char *);
 extern "C" int __dlapi_reverse(const void *, __dlapi_symbol *);
 extern "C" int __dlapi_close(void *);
+extern "C" int __dlapi_find_object(void *__address, dl_find_object *__result);
 
 int dlclose(void *handle) {
 	return __dlapi_close(handle);
@@ -91,4 +92,8 @@ int dlinfo(void *__restrict, int, void *__restrict) {
 	__builtin_unreachable();
 }
 
+int _dl_find_object(void *address, struct dl_find_object *result) {
+	return __dlapi_find_object(address, result);
+}
+
 #endif // __MLIBC_GLIBC_OPTION

options/posix/generic/sys-uio.cpp

@@ -29,6 +29,19 @@ ssize_t writev(int fd, const struct iovec *iovs, int iovc) {
 	__ensure(iovc);
 
 	ssize_t written = 0;
+
+	auto sysdep = mlibc::sys_writev;
+	if(sysdep) {
+		int e = sysdep(fd, iovs, iovc, &written);
+		if(e) {
+			errno = e;
+			return -1;
+		}
+		return written;
+	}
+
+	// TODO: this implementation is not safe to use in signal contexts
+	mlibc::infoLogger() << "mlibc: falling back to signal-unsafe writev implementation!" << frg::endlog;
 	size_t bytes = 0;
 	for(int i = 0; i < iovc; i++) {
 		if(SSIZE_MAX - bytes < iovs[i].iov_len) {

options/posix/include/mlibc/posix-sysdeps.hpp

@@ -52,6 +52,7 @@ int sys_read(int fd, void *buf, size_t count, ssize_t *bytes_read);
 [[gnu::weak]] int sys_readv(int fd, const struct iovec *iovs, int iovc, ssize_t *bytes_read);
 
 int sys_write(int fd, const void *buf, size_t count, ssize_t *bytes_written);
+[[gnu::weak]] int sys_writev(int fd, const struct iovec *iovs, int iovc, ssize_t *bytes_written);
 [[gnu::weak]] int sys_pread(int fd, void *buf, size_t n, off_t off, ssize_t *bytes_read);
 [[gnu::weak]] int sys_pwrite(int fd, const void *buf, size_t n, off_t off, ssize_t *bytes_read);
 

options/rtld/aarch64/entry.S

@@ -1,11 +1,13 @@
+#include "mlibc-asm/helpers.h"
 
-.global _start
-_start:
+PROC_START(_start)
 	bl relocateSelf
 
 	mov x0, sp
 	bl interpreterMain
 
 	br x0
+PROC_END(_start)
+
 .section .note.GNU-stack,"",%progbits