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gas data sizes

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Ciro Santilli 六四事件 法轮功
2019-05-09 00:00:01 +00:00
parent 5e55547ce1
commit 7014d34576
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README.adoc
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@@ -9,7 +9,7 @@
:toclevels: 6
:toc-title:
The perfect emulation setup to study and develop the <<linux-kernel>>, kernel modules, <<qemu-buildroot-setup,QEMU>> and <<userland-assembly,userland>> and <<baremetal-setup,baremetal>> assembly. Highly automated. Thoroughly documented. <<gdb>> and <<kgdb>> just work. Automated <<test-this-repo,tests>>. Powered by <<about-the-qemu-buildroot-setup,Buildroot>> and <<about-the-baremetal-setup,crosstool-NG>>. "Tested" in Ubuntu 18.04 host, x86_64, ARMv7 and ARMv8 guests with kernel v5.0.
The perfect emulation setup to study and develop the <<linux-kernel>> v5.0, kernel modules, <<qemu-buildroot-setup,QEMU>> and x86_64, ARMv7 and ARMv8 <<userland-assembly,userland>> and <<baremetal-setup,baremetal>> assembly. <<gdb>> and <<kgdb>> just work. Powered by <<about-the-qemu-buildroot-setup,Buildroot>> and <<about-the-baremetal-setup,crosstool-NG>>. Highly automated. Thoroughly documented. Automated <<test-this-repo,tests>>. "Tested" in an Ubuntu 18.04 host.
TL;DR: <<qemu-buildroot-setup-getting-started>>
@@ -11603,7 +11603,7 @@ and notice how the error message gives both:
* the actual assembly source line number where the failing assert was
* the actual and expected values
Other setup sanity checks that you might want to look into include:
Other infrastructure sanity checks that you might want to look into include:
* link:userland/arch/empty.S[]
* `FAIL` tests
@@ -11658,7 +11658,7 @@ In order to GDB step debug those executables, you will want to use `--no-continu
You are now left on the very first instruction of our tiny executable!
=== Inline assembly
=== GCC inline assembly
Examples under `arch/<arch>/c/` directories show to how use inline assembly from higher level languages such as C:
@@ -11774,6 +11774,56 @@ Bibliography:
* http://stackoverflow.com/questions/261419/arm-to-c-calling-convention-registers-to-save
* https://stackoverflow.com/questions/10494848/arm-whats-the-difference-between-apcs-and-aapcs-abi
=== GAS directives
==== GAS data sizes
Let's see how may bytes go into each data type:
* link:userland/arch/x86_64/gas_data_sizes.S[]
* link:userland/arch/arm/gas_data_sizes.S[]
* link:userland/arch/aarch64/gas_data_sizes.S[]
Conclusion:
[options="header"]
|===
|byte |word |long |quad |octa
|x86
|1
|2
|4
|8
|16
|arm
|1
|4
|4
|8
|16
|aarch64
|1
|4
|4
|8
|16
|===
and also keep in mind that:
* `.int` is the same as `.long`
* `.hword` is the same as `.short` which is usually the same as `.word`
Bibliography:
* https://sourceware.org/binutils/docs-2.32/as/Pseudo-Ops.html#Pseudo-Ops
* https://stackoverflow.com/questions/43005411/how-does-the-quad-directive-work-in-assembly/43006616
* https://gist.github.com/steakknife/d47d0b19a24817f48027
== x86 userland assembly
Arch agnostic infrastructure getting started at: <<userland-assembly>>.
@@ -14449,6 +14499,11 @@ We haven't found the ultimate distro yet, here is a summary table of trade-offs
* (7): `ls recipes-* | wc`
* (8): Poky reference system: http://git.yoctoproject.org/cgit/cgit.cgi/poky
Other interesting possibilities that I haven't evaluated well:
* NixOS https://nixos.org/ Seems to support full build from source well. Not much cross compilation information however.
* Gentoo https://en.wikipedia.org/wiki/Gentoo_Linux Seems to support full build from source well.
=== Soft topics
==== Fairy tale