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Merge pull request #245 from LagoLunatic/subi

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PPC pooled data references: Add support for `subi`, `addis`, and `subis` instructions
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LagoLunatic 2025-08-23 18:05:47 -04:00 committed by GitHub
commit 48804dc2e3
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1 changed files with 52 additions and 14 deletions
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62
objdiff-core/src/arch/ppc/mod.rs
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@ -675,7 +675,7 @@ fn make_symbol_ref(symbol: &object::Symbol) -> Result<ExtabSymbolRef> {
#[derive(Debug)]
struct PoolReference {
addr_src_gpr: powerpc::GPR,
addr_offset: i16,
addr_offset: i64,
addr_dst_gpr: Option<powerpc::GPR>,
}
@ -683,16 +683,20 @@ struct PoolReference {
// If so, return information pertaining to where the instruction is getting that address from and
// what it's doing with the address (e.g. copying it into another register, adding an offset, etc).
fn get_pool_reference_for_inst(
opcode: powerpc::Opcode,
ins: powerpc::Ins,
simplified: &powerpc::ParsedIns,
) -> Option<PoolReference> {
use powerpc::{Argument, Opcode};
let args = &simplified.args;
if flow_analysis::guess_data_type_from_load_store_inst_op(opcode).is_some() {
if flow_analysis::guess_data_type_from_load_store_inst_op(ins.op).is_some() {
match (args[1], args[2]) {
(Argument::Offset(offset), Argument::GPR(addr_src_gpr)) => {
// e.g. lwz. Immediate offset.
Some(PoolReference { addr_src_gpr, addr_offset: offset.0, addr_dst_gpr: None })
Some(PoolReference {
addr_src_gpr,
addr_offset: offset.0 as i64,
addr_dst_gpr: None,
})
}
(Argument::GPR(addr_src_gpr), Argument::GPR(_offset_gpr)) => {
// e.g. lwzx. The offset is in a register and was likely calculated from an index.
@ -712,17 +716,51 @@ fn get_pool_reference_for_inst(
// If either of these match, we also want to return the destination register that the
// address is being copied into so that we can detect any future references to that new
// register as well.
match (opcode, args[0], args[1], args[2]) {
match (ins.op, args[0], args[1], args[2]) {
(
// `addi` or `subi`
Opcode::Addi,
Argument::GPR(addr_dst_gpr),
Argument::GPR(addr_src_gpr),
Argument::Simm(simm),
) => Some(PoolReference {
) => {
let offset = if simplified.mnemonic == "addi" { simm.0 } else { -simm.0 };
Some(PoolReference {
addr_src_gpr,
addr_offset: simm.0,
addr_offset: offset as i64,
addr_dst_gpr: Some(addr_dst_gpr),
}),
})
}
(
// `addis`
Opcode::Addis,
Argument::GPR(addr_dst_gpr),
Argument::GPR(addr_src_gpr),
Argument::Uimm(uimm), // Note: `addis` uses UIMM, unlike `addi`, `subi`, and `subis`
) => {
assert_eq!(simplified.mnemonic, "addis");
let offset = (uimm.0 as i64) << 16;
Some(PoolReference {
addr_src_gpr,
addr_offset: offset,
addr_dst_gpr: Some(addr_dst_gpr),
})
}
(
// `subis`
Opcode::Addis,
Argument::GPR(addr_dst_gpr),
Argument::GPR(addr_src_gpr),
Argument::Simm(simm),
) => {
assert_eq!(simplified.mnemonic, "subis");
let offset = (simm.0 as i64) << 16;
Some(PoolReference {
addr_src_gpr,
addr_offset: offset,
addr_dst_gpr: Some(addr_dst_gpr),
})
}
(
// `mr` or `mr.`
Opcode::Or,
@ -777,13 +815,13 @@ fn clear_overwritten_gprs(ins: powerpc::Ins, gpr_pool_relocs: &mut BTreeMap<u8,
// Also, if this instruction is accessing the middle of a symbol instead of the start, we add an
// addend to indicate that.
fn make_fake_pool_reloc(
offset: i16,
offset: i64,
cur_addr: u32,
pool_reloc: &Relocation,
symbols: &[Symbol],
) -> Option<Relocation> {
let pool_reloc = resolve_relocation(symbols, pool_reloc);
let offset_from_pool = pool_reloc.relocation.addend + offset as i64;
let offset_from_pool = pool_reloc.relocation.addend + offset;
let target_address = pool_reloc.symbol.address.checked_add_signed(offset_from_pool)?;
let target_symbol;
let addend;
@ -946,7 +984,7 @@ fn generate_fake_pool_relocations_for_function(
clear_overwritten_gprs(ins, &mut gpr_pool_relocs);
}
}
} else if let Some(pool_ref) = get_pool_reference_for_inst(ins.op, &simplified) {
} else if let Some(pool_ref) = get_pool_reference_for_inst(ins, &simplified) {
// This instruction doesn't have a real relocation, so it may be a reference to one of
// the already-loaded pools.
if let Some(pool_reloc) = gpr_pool_relocs.get(&pool_ref.addr_src_gpr.0) {
@ -965,7 +1003,7 @@ fn generate_fake_pool_relocations_for_function(
// with the offset within the .data section of an array variable into r21.
// Then the body of the loop will `lwzx` one of the array elements from r21.
let mut new_reloc = pool_reloc.clone();
new_reloc.addend += pool_ref.addr_offset as i64;
new_reloc.addend += pool_ref.addr_offset;
gpr_pool_relocs.insert(addr_dst_gpr.0, new_reloc);
} else {
clear_overwritten_gprs(ins, &mut gpr_pool_relocs);