From d2f93094b2c848b839b25b7565cb6d4bde7f15c2 Mon Sep 17 00:00:00 2001
From: Jason Hiser <jdhiser@gmail.com>
Date: Mon, 2 Dec 2019 09:42:36 -0500
Subject: [PATCH] mips updates
---
include/arch/arch_mips32.hpp | 4 +--
src/patcher_mips32.cpp | 57 +++++++++++++-----------------------
src/pinner_mips32.cpp | 7 +++--
3 files changed, 27 insertions(+), 41 deletions(-)
diff --git a/include/arch/arch_mips32.hpp b/include/arch/arch_mips32.hpp
index 0d1bf4352..5746425db 100644
--- a/include/arch/arch_mips32.hpp
+++ b/include/arch/arch_mips32.hpp
@@ -10,8 +10,8 @@ class ZiprArchitectureHelperMIPS32_t : public ZiprArchitectureHelperBase_t
virtual IRDB_SDK::Instruction_t* createNewJumpInstruction(IRDB_SDK::FileIR_t *p_firp, IRDB_SDK::Instruction_t* p_existing) override
{
- // bytes = 0b00000000 0b00000000 0b00000000 0b00010000
- // jump always with 26bit offset
+ // create a beq $0, $0, imm16 instruction
+ // to be PC-relative.
const auto bits =string("\x10\x00\x00\x000",4);
auto ret=IRDB_SDK::addNewDataBits(p_firp, p_existing, bits);
const auto d=IRDB_SDK::DecodedInstruction_t::factory(ret);
diff --git a/src/patcher_mips32.cpp b/src/patcher_mips32.cpp
index ec147ecd4..392a57175 100644
--- a/src/patcher_mips32.cpp
+++ b/src/patcher_mips32.cpp
@@ -64,43 +64,28 @@ void ZiprPatcherMIPS32_t::ApplyNopToPatch(RangeAddress_t addr)
void ZiprPatcherMIPS32_t::ApplyPatch(RangeAddress_t from_addr, RangeAddress_t to_addr)
{
+#if 0
const auto first_byte = (uint8_t)memory_space[from_addr+0];
- const auto new_offset = (int32_t)((to_addr) - (from_addr+8)) >> 2;
-
- // A Branch in binary is: op= 000010 imm26=0000 00000000 00000000 00000000
- // it includes a 26-bit immediate, which is +/- 128mb, which should be a good enough "jump anywhere"
- // for now.
- const auto mask6 = (0b111111);
- const auto is_uncond_branch = ((first_byte >> 2) & mask6) == (0b000010); // jump branch
-
- if(is_uncond_branch)
- {
- cout<<"Applying uncond branch patch from "<<hex<<from_addr<<" to "<<to_addr<<endl;
- const auto non_imm_bits = 32U-26U; // 32 bits - imm26
- // assert there's no overflow.
- assert((int64_t)(new_offset << non_imm_bits) == ((int64_t)new_offset) << non_imm_bits);
- // or in opcode for first byte. set remaining bytes.
- const auto mask26 = ((1<<26)-1);
- const auto trimmed_offset = new_offset & mask26;
- memory_space[from_addr+3] = (trimmed_offset>> 0)&0xff;
- memory_space[from_addr+2] = (trimmed_offset>> 8)&0xff;
- memory_space[from_addr+1] = (trimmed_offset>>16)&0xff;
- memory_space[from_addr+0] |= (trimmed_offset>>24)&0x02;
- }
- else
- {
- cout<<"Applying cond branch patch from "<<hex<<from_addr<<" to "<<to_addr<<endl;
- const auto non_imm_bits = 32U-24U; // 32 bits - imm24
- // assert there's no overflow.
- assert((int64_t)(new_offset << non_imm_bits) == ((int64_t)new_offset) << non_imm_bits);
- // or in opcode for first byte. set remaining bytes.
- const auto mask24 = ((1<<24)-1);
- const auto trimmed_offset = new_offset & mask24;
- memory_space[from_addr+3] = (trimmed_offset>> 0)&0xff;
- memory_space[from_addr+2] = (trimmed_offset>> 8)&0xff;
- memory_space[from_addr+1] = (trimmed_offset>>16)&0xff;
- memory_space[from_addr+0] |= (trimmed_offset>>24)&0x02;
- }
+ assert(first_byte == 0x10); // beq $0
+#endif
+
+ const auto new_offset = (int32_t)((to_addr) - (from_addr+4)) >> 2;
+
+
+ // Use a branch always. In mips, this will be a beq $0, $0, <label> as there is no branch always.
+ // format: 0001 00ss sstt iiii iiii iiii iiii iiii
+ // ssss=0b0000
+ // tttt=0b0000
+ // i...i = (from_addr-to_addr)>>2
+ cout<<"Applying cond branch patch from "<<hex<<from_addr<<" to "<<to_addr<<endl;
+ const auto non_imm_bits = 16;
+ // assert there's no overflow.
+ assert((int64_t)(new_offset << non_imm_bits) == ((int64_t)new_offset) << non_imm_bits);
+ // or in opcode for first byte. set remaining bytes.
+ const auto mask16 = ((1<<16)-1);
+ const auto trimmed_offset = new_offset & mask16;
+ memory_space[from_addr+3] = (trimmed_offset>> 0)&0xff;
+ memory_space[from_addr+2] = (trimmed_offset>> 8)&0xff;
}
diff --git a/src/pinner_mips32.cpp b/src/pinner_mips32.cpp
index f006e3a6b..2627aa1b1 100644
--- a/src/pinner_mips32.cpp
+++ b/src/pinner_mips32.cpp
@@ -41,9 +41,10 @@ void ZiprPinnerMIPS32_t::doPinning()
auto ibta_addr=(RangeAddress_t)insn-> getIndirectBranchTargetAddress()-> getVirtualOffset();
- // put unconditional branch with 24-bit offset in memory
- // 1110 1010 0000 0000 0000 0000 0000 0000
- uint8_t bytes[]={'\x18','\x00','\x00','\x00'};
+ // put branch with 16-bit offset in memory
+ // i.e., beq $0, $0, imm16
+ // including putting a nop in the delay slot.
+ uint8_t bytes[]={'\x10','\x00','\x00','\x00', '\x00', '\x00', '\x00', '\x00'};
for(auto i=0U;i<sizeof(bytes);i++)
{
const auto ibta_byte_addr = ibta_addr+i;
--
GitLab