From 20745264ce3298147067fcb46e1f51efcb9670e4 Mon Sep 17 00:00:00 2001 From: Ed Schouten Date: Mon, 8 Jan 2018 10:51:25 +0100 Subject: Implement libstd for CloudABI. Though CloudABI is strongly inspired by POSIX, its absence of features that don't work well with capability-based sandboxing makes it different enough that adding bits to sys/unix will make things a mess. This change therefore adds CloudABI specific platform code under sys/cloudabi and borrows parts from sys/unix that can be used without changes. One of the goals of this implementation is to build as much as possible directly on top of CloudABI's system call layer, as opposed to using the C library. This is preferred, as the system call layer is supposed to be stable, whereas the C library ABI technically is not. An advantage of this approach is that it allows us to implement certain interfaces, such as mutexes and condition variables more optimally. They can be lighter than the ones provided by pthreads. This change disables some modules that cannot realistically be implemented right now. For example, libstd's pathname abstraction is not designed with POSIX *at() (e.g., openat()) in mind. The *at() functions are the only set of file system APIs available on CloudABI. There is no global file system namespace, nor a process working directory. Discussions on how to port these modules over are outside the scope of this change. Apart from this change, there are still some other minor fixups that need to be made to platform independent code to make things build. These will be sent out separately, so they can be reviewed more thoroughly. --- src/libstd/sys/cloudabi/backtrace.rs | 121 +++++++++++++++++++++++++++++++++++ 1 file changed, 121 insertions(+) create mode 100644 src/libstd/sys/cloudabi/backtrace.rs (limited to 'src/libstd/sys/cloudabi/backtrace.rs') diff --git a/src/libstd/sys/cloudabi/backtrace.rs b/src/libstd/sys/cloudabi/backtrace.rs new file mode 100644 index 00000000000..33d93179237 --- /dev/null +++ b/src/libstd/sys/cloudabi/backtrace.rs @@ -0,0 +1,121 @@ +// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +use error::Error; +use ffi::CStr; +use intrinsics; +use io; +use libc; +use sys_common::backtrace::Frame; +use unwind as uw; + +pub struct BacktraceContext; + +struct Context<'a> { + idx: usize, + frames: &'a mut [Frame], +} + +#[derive(Debug)] +struct UnwindError(uw::_Unwind_Reason_Code); + +impl Error for UnwindError { + fn description(&self) -> &'static str { + "unexpected return value while unwinding" + } +} + +impl ::fmt::Display for UnwindError { + fn fmt(&self, f: &mut ::fmt::Formatter) -> ::fmt::Result { + write!(f, "{}: {:?}", self.description(), self.0) + } +} + +#[inline(never)] // if we know this is a function call, we can skip it when + // tracing +pub fn unwind_backtrace(frames: &mut [Frame]) -> io::Result<(usize, BacktraceContext)> { + let mut cx = Context { idx: 0, frames }; + let result_unwind = + unsafe { uw::_Unwind_Backtrace(trace_fn, &mut cx as *mut Context as *mut libc::c_void) }; + // See libunwind:src/unwind/Backtrace.c for the return values. + // No, there is no doc. + match result_unwind { + // These return codes seem to be benign and need to be ignored for backtraces + // to show up properly on all tested platforms. + uw::_URC_END_OF_STACK | uw::_URC_FATAL_PHASE1_ERROR | uw::_URC_FAILURE => { + Ok((cx.idx, BacktraceContext)) + } + _ => Err(io::Error::new( + io::ErrorKind::Other, + UnwindError(result_unwind), + )), + } +} + +extern "C" fn trace_fn( + ctx: *mut uw::_Unwind_Context, + arg: *mut libc::c_void, +) -> uw::_Unwind_Reason_Code { + let cx = unsafe { &mut *(arg as *mut Context) }; + let mut ip_before_insn = 0; + let mut ip = unsafe { uw::_Unwind_GetIPInfo(ctx, &mut ip_before_insn) as *mut libc::c_void }; + if !ip.is_null() && ip_before_insn == 0 { + // this is a non-signaling frame, so `ip` refers to the address + // after the calling instruction. account for that. + ip = (ip as usize - 1) as *mut _; + } + + let symaddr = unsafe { uw::_Unwind_FindEnclosingFunction(ip) }; + if cx.idx < cx.frames.len() { + cx.frames[cx.idx] = Frame { + symbol_addr: symaddr as *mut u8, + exact_position: ip as *mut u8, + }; + cx.idx += 1; + } + + uw::_URC_NO_REASON +} + +pub fn foreach_symbol_fileline(_: Frame, _: F, _: &BacktraceContext) -> io::Result +where + F: FnMut(&[u8], u32) -> io::Result<()>, +{ + // No way to obtain this information on CloudABI. + Ok(false) +} + +pub fn resolve_symname(frame: Frame, callback: F, _: &BacktraceContext) -> io::Result<()> +where + F: FnOnce(Option<&str>) -> io::Result<()>, +{ + unsafe { + let mut info: Dl_info = intrinsics::init(); + let symname = + if dladdr(frame.exact_position as *mut _, &mut info) == 0 || info.dli_sname.is_null() { + None + } else { + CStr::from_ptr(info.dli_sname).to_str().ok() + }; + callback(symname) + } +} + +#[repr(C)] +struct Dl_info { + dli_fname: *const libc::c_char, + dli_fbase: *mut libc::c_void, + dli_sname: *const libc::c_char, + dli_saddr: *mut libc::c_void, +} + +extern "C" { + fn dladdr(addr: *const libc::c_void, info: *mut Dl_info) -> libc::c_int; +} -- cgit 1.4.1-3-g733a5