From 366df8852f503523cc4f9046d82ba9a99dd51d7f Mon Sep 17 00:00:00 2001 From: Akshay Date: Sun, 12 Feb 2023 12:13:49 +0530 Subject: new art: lapse --- docs/posts/call_to_ARMs/index.html | 49 ++++++++++++++++++++++++++++---------- 1 file changed, 36 insertions(+), 13 deletions(-) (limited to 'docs/posts/call_to_ARMs/index.html') diff --git a/docs/posts/call_to_ARMs/index.html b/docs/posts/call_to_ARMs/index.html index 3331107..1b13213 100644 --- a/docs/posts/call_to_ARMs/index.html +++ b/docs/posts/call_to_ARMs/index.html @@ -33,7 +33,7 @@ cm   - 2.2 + 2.3 min @@ -42,37 +42,60 @@ Call To ARMs
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My 4th semester involves ARM programming. And proprietary tooling (Keil C). But we don’t do that here.

+

My 4th semester involves ARM programming. And proprietary tooling +(Keil C). But we don’t do that here.

Building

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Assembling and linking ARM binaries on non-ARM architecture devices is fairly trivial. I went along with the GNU cross bare metal toolchain binutils, which provides arm-as and arm-ld (among a bunch of other utils that I don’t care about for now).

+

Assembling and linking ARM binaries on non-ARM architecture devices +is fairly trivial. I went along with the GNU cross bare metal toolchain +binutils, which provides arm-as and arm-ld +(among a bunch of other utils that I don’t care about for now).

Assemble .s files with:

arm-none-eabi-as main.s -g -march=armv8.1-a -o main.out
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The -g flag generates extra debugging information that gdb picks up. The -march option establishes target architecture.

+

The -g flag generates extra debugging information that +gdb picks up. The -march option establishes +target architecture.

Link .o files with:

arm-none-eabi-ld main.out -o main

Running (and Debugging)

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Things get interesting here. gdb on your x86 machine cannot read nor execute binaries compiled for ARM. So, we simulate an ARM processor using qemu. Now qemu allows you to run gdbserver on startup. Connecting our local gdb instance to gdbserver gives us a view into the program’s execution. Easy!

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Run qemu, with gdbserver on port 1234, with our ARM binary, main:

+

Things get interesting here. gdb on your x86 machine +cannot read nor execute binaries compiled for ARM. So, we simulate an +ARM processor using qemu. Now qemu allows you to run +gdbserver on startup. Connecting our local gdb +instance to gdbserver gives us a view into the program’s +execution. Easy!

+

Run qemu, with gdbserver on port +1234, with our ARM binary, main:

qemu-arm -singlestep -g 1234 main
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Start up gdb on your machine, and connect to qemu’s gdbserver:

+

Start up gdb on your machine, and connect to +qemu’s gdbserver:

(gdb) set architecture armv8-a
 (gdb) target remote localhost:1234
 (gdb) file main
 Reading symbols from main...  # yay!

GDB Enhanced

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gdb is cool, but it’s not nearly as comfortable as well fleshed out emulators/IDEs like Keil. Watching registers, CPSR and memory chunks update is pretty fun.

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I came across gdb’s TUI mode (hit C-x C-a or type tui enable at the prompt). TUI mode is a godsend. It highlights the current line of execution, shows you disassembly outputs, updated registers, active breakpoints and more.

+

gdb is cool, but it’s not nearly as comfortable as well +fleshed out emulators/IDEs like Keil. Watching registers, CPSR and +memory chunks update is pretty fun.

+

I came across gdb’s TUI mode (hit C-x C-a +or type tui enable at the prompt). TUI mode is a godsend. +It highlights the current line of execution, shows you disassembly +outputs, updated registers, active breakpoints and more.

But, it is an absolute eyesore.

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Say hello to GEF! “GDB Enhanced Features” teaches our old dog some cool new tricks. Here are some additions that made my ARM debugging experience loads better:

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Say hello to GEF! “GDB +Enhanced Features” teaches our old dog some cool new tricks. Here are +some additions that made my ARM debugging experience loads better:

And it’s pretty! See for yourself:

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+

Editing

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Vim, with syntax off because it dosen’t handle GNU ARM syntax too well.

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Vim, with syntax off because it dosen’t handle GNU ARM +syntax too well.

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