Foundations of Linux ARM64: Debug, Disassemble, and Reverse/

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Reconstructing the C/C++ Code

Reconstructing the C/C++ Code

Learn how to reconstruct a code in the C/C++ language with the help of the GDB disassembly output in the non-optimization mode.

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Mixed assembly/pseudocode code

Now, we go from instruction to instruction and try to reconstruct the pseudocode, which is shown as comments against assembly language code.

adrp    x0, 0x420000
add     x0, x0, #0x30          // x0 <- address var1 (0x420030)
adrp    x1, 0x420000           //
add     x1, x1, #0x28          // x1 <- address var2 (0x420028)
str     x1, [x0]               // [x0] <- x1
adrp    x0, 0x420000           //
add     x0, x0, #0x38          // x0 <- address var3 (0x420038)
adrp    x1, 0x420000
add     x1, x1, #0x2c          // x1 <- address var4 (0x42002c)
str     x1, [x0]               // [x0] <- x1

This code calculates the effective address, which it stores in a register. It then assigns the register value to the integer pointer. We do the same process for the other variable and store the other register value to the other integer pointer.

adrp    x0, 0x420000
add     x0, x0, #0x30     // x0 <- address var1 (0x420030)
ldr     x0, [x0]          // x0 <- [x0]
mov     w1, #0x1          // w1 <- 1
str     w1, [x0]          // [x0] <- w1
adrp    x0, 0x420000
add     x0, x0, #0x38     // x0 <- address var3 (0x420038)
ldr     x0, [x0]          // x0 <- [x0]
mov     w1, #0x1          // w1 <- 1
str     w1, [x0]          // [x0] <- w1

The code snippet ...