From d1b2d29528b7794b41e66fc2136e395a02f8529b Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 30 May 2024 05:59:35 +0200 Subject: Merging upstream version 1.73.0+dfsg1. Signed-off-by: Daniel Baumann --- library/std/src/sys/personality/dwarf/eh.rs | 208 ++++++++++++++++++++++++++++ 1 file changed, 208 insertions(+) create mode 100644 library/std/src/sys/personality/dwarf/eh.rs (limited to 'library/std/src/sys/personality/dwarf/eh.rs') diff --git a/library/std/src/sys/personality/dwarf/eh.rs b/library/std/src/sys/personality/dwarf/eh.rs new file mode 100644 index 000000000..79624703a --- /dev/null +++ b/library/std/src/sys/personality/dwarf/eh.rs @@ -0,0 +1,208 @@ +//! Parsing of GCC-style Language-Specific Data Area (LSDA) +//! For details see: +//! * +//! * +//! * +//! * +//! +//! A reference implementation may be found in the GCC source tree +//! (`/libgcc/unwind-c.c` as of this writing). + +#![allow(non_upper_case_globals)] +#![allow(unused)] + +use super::DwarfReader; +use core::mem; +use core::ptr; + +pub const DW_EH_PE_omit: u8 = 0xFF; +pub const DW_EH_PE_absptr: u8 = 0x00; + +pub const DW_EH_PE_uleb128: u8 = 0x01; +pub const DW_EH_PE_udata2: u8 = 0x02; +pub const DW_EH_PE_udata4: u8 = 0x03; +pub const DW_EH_PE_udata8: u8 = 0x04; +pub const DW_EH_PE_sleb128: u8 = 0x09; +pub const DW_EH_PE_sdata2: u8 = 0x0A; +pub const DW_EH_PE_sdata4: u8 = 0x0B; +pub const DW_EH_PE_sdata8: u8 = 0x0C; + +pub const DW_EH_PE_pcrel: u8 = 0x10; +pub const DW_EH_PE_textrel: u8 = 0x20; +pub const DW_EH_PE_datarel: u8 = 0x30; +pub const DW_EH_PE_funcrel: u8 = 0x40; +pub const DW_EH_PE_aligned: u8 = 0x50; + +pub const DW_EH_PE_indirect: u8 = 0x80; + +#[derive(Copy, Clone)] +pub struct EHContext<'a> { + pub ip: usize, // Current instruction pointer + pub func_start: usize, // Address of the current function + pub get_text_start: &'a dyn Fn() -> usize, // Get address of the code section + pub get_data_start: &'a dyn Fn() -> usize, // Get address of the data section +} + +pub enum EHAction { + None, + Cleanup(usize), + Catch(usize), + Filter(usize), + Terminate, +} + +pub const USING_SJLJ_EXCEPTIONS: bool = cfg!(all(target_os = "ios", target_arch = "arm")); + +pub unsafe fn find_eh_action(lsda: *const u8, context: &EHContext<'_>) -> Result { + if lsda.is_null() { + return Ok(EHAction::None); + } + + let func_start = context.func_start; + let mut reader = DwarfReader::new(lsda); + + let start_encoding = reader.read::(); + // base address for landing pad offsets + let lpad_base = if start_encoding != DW_EH_PE_omit { + read_encoded_pointer(&mut reader, context, start_encoding)? + } else { + func_start + }; + + let ttype_encoding = reader.read::(); + if ttype_encoding != DW_EH_PE_omit { + // Rust doesn't analyze exception types, so we don't care about the type table + reader.read_uleb128(); + } + + let call_site_encoding = reader.read::(); + let call_site_table_length = reader.read_uleb128(); + let action_table = reader.ptr.add(call_site_table_length as usize); + let ip = context.ip; + + if !USING_SJLJ_EXCEPTIONS { + while reader.ptr < action_table { + let cs_start = read_encoded_pointer(&mut reader, context, call_site_encoding)?; + let cs_len = read_encoded_pointer(&mut reader, context, call_site_encoding)?; + let cs_lpad = read_encoded_pointer(&mut reader, context, call_site_encoding)?; + let cs_action_entry = reader.read_uleb128(); + // Callsite table is sorted by cs_start, so if we've passed the ip, we + // may stop searching. + if ip < func_start + cs_start { + break; + } + if ip < func_start + cs_start + cs_len { + if cs_lpad == 0 { + return Ok(EHAction::None); + } else { + let lpad = lpad_base + cs_lpad; + return Ok(interpret_cs_action(action_table as *mut u8, cs_action_entry, lpad)); + } + } + } + // Ip is not present in the table. This indicates a nounwind call. + Ok(EHAction::Terminate) + } else { + // SjLj version: + // The "IP" is an index into the call-site table, with two exceptions: + // -1 means 'no-action', and 0 means 'terminate'. + match ip as isize { + -1 => return Ok(EHAction::None), + 0 => return Ok(EHAction::Terminate), + _ => (), + } + let mut idx = ip; + loop { + let cs_lpad = reader.read_uleb128(); + let cs_action_entry = reader.read_uleb128(); + idx -= 1; + if idx == 0 { + // Can never have null landing pad for sjlj -- that would have + // been indicated by a -1 call site index. + let lpad = (cs_lpad + 1) as usize; + return Ok(interpret_cs_action(action_table as *mut u8, cs_action_entry, lpad)); + } + } + } +} + +unsafe fn interpret_cs_action( + action_table: *mut u8, + cs_action_entry: u64, + lpad: usize, +) -> EHAction { + if cs_action_entry == 0 { + // If cs_action_entry is 0 then this is a cleanup (Drop::drop). We run these + // for both Rust panics and foreign exceptions. + EHAction::Cleanup(lpad) + } else { + // If lpad != 0 and cs_action_entry != 0, we have to check ttype_index. + // If ttype_index == 0 under the condition, we take cleanup action. + let action_record = (action_table as *mut u8).offset(cs_action_entry as isize - 1); + let mut action_reader = DwarfReader::new(action_record); + let ttype_index = action_reader.read_sleb128(); + if ttype_index == 0 { + EHAction::Cleanup(lpad) + } else if ttype_index > 0 { + // Stop unwinding Rust panics at catch_unwind. + EHAction::Catch(lpad) + } else { + EHAction::Filter(lpad) + } + } +} + +#[inline] +fn round_up(unrounded: usize, align: usize) -> Result { + if align.is_power_of_two() { Ok((unrounded + align - 1) & !(align - 1)) } else { Err(()) } +} + +unsafe fn read_encoded_pointer( + reader: &mut DwarfReader, + context: &EHContext<'_>, + encoding: u8, +) -> Result { + if encoding == DW_EH_PE_omit { + return Err(()); + } + + // DW_EH_PE_aligned implies it's an absolute pointer value + if encoding == DW_EH_PE_aligned { + reader.ptr = reader.ptr.with_addr(round_up(reader.ptr.addr(), mem::size_of::())?); + return Ok(reader.read::()); + } + + let mut result = match encoding & 0x0F { + DW_EH_PE_absptr => reader.read::(), + DW_EH_PE_uleb128 => reader.read_uleb128() as usize, + DW_EH_PE_udata2 => reader.read::() as usize, + DW_EH_PE_udata4 => reader.read::() as usize, + DW_EH_PE_udata8 => reader.read::() as usize, + DW_EH_PE_sleb128 => reader.read_sleb128() as usize, + DW_EH_PE_sdata2 => reader.read::() as usize, + DW_EH_PE_sdata4 => reader.read::() as usize, + DW_EH_PE_sdata8 => reader.read::() as usize, + _ => return Err(()), + }; + + result += match encoding & 0x70 { + DW_EH_PE_absptr => 0, + // relative to address of the encoded value, despite the name + DW_EH_PE_pcrel => reader.ptr.expose_addr(), + DW_EH_PE_funcrel => { + if context.func_start == 0 { + return Err(()); + } + context.func_start + } + DW_EH_PE_textrel => (*context.get_text_start)(), + DW_EH_PE_datarel => (*context.get_data_start)(), + _ => return Err(()), + }; + + if encoding & DW_EH_PE_indirect != 0 { + result = *ptr::from_exposed_addr::(result); + } + + Ok(result) +} -- cgit v1.2.3