a88603f4b9
The Go runtime uses r30 for some special value called 'g'. It assumes
that value will remain unchanged even when calling VDSO functions.
Although r30 is non-volatile across function calls, the callee is free
to use it, as long as the callee saves the value and restores it before
returning.
It used to be true by accident that the VDSO didn't use r30, because the
VDSO was hand-written asm. When we switched to building the VDSO from C
the compiler started using r30, at least in some builds, leading to
crashes in Go. eg:
~/go/src$ ./all.bash
Building Go cmd/dist using /usr/lib/go-1.16. (go1.16.2 linux/ppc64le)
Building Go toolchain1 using /usr/lib/go-1.16.
go build os/exec: /usr/lib/go-1.16/pkg/tool/linux_ppc64le/compile: signal: segmentation fault
go build reflect: /usr/lib/go-1.16/pkg/tool/linux_ppc64le/compile: signal: segmentation fault
go tool dist: FAILED: /usr/lib/go-1.16/bin/go install -gcflags=-l -tags=math_big_pure_go compiler_bootstrap bootstrap/cmd/...: exit status 1
There are patches in flight to fix Go[1], but until they are released
and widely deployed we can workaround it in the VDSO by avoiding use of
r30.
Note this only works with GCC, clang does not support -ffixed-rN.
1: https://go-review.googlesource.com/c/go/+/328110
Fixes:
|
||
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.