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[ Upstream commit 0ceb1ace4a ]
In https://bugs.gentoo.org/769614 Dmitry noticed that
`ptrace(PTRACE_GET_SYSCALL_INFO)` does not work for syscalls called via
glibc's syscall() wrapper.
ia64 has two ways to call syscalls from userspace: via `break` and via
`eps` instructions.
The difference is in stack layout:
1. `eps` creates simple stack frame: no locals, in{0..7} == out{0..8}
2. `break` uses userspace stack frame: may be locals (glibc provides
one), in{0..7} == out{0..8}.
Both work fine in syscall handling cde itself.
But `ptrace(PTRACE_GET_SYSCALL_INFO)` uses unwind mechanism to
re-extract syscall arguments but it does not account for locals.
The change always skips locals registers. It should not change `eps`
path as kernel's handler already enforces locals=0 and fixes `break`.
Tested on v5.10 on rx3600 machine (ia64 9040 CPU).
Link: https://lkml.kernel.org/r/20210221002554.333076-1-slyfox@gentoo.org
Link: https://bugs.gentoo.org/769614
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Reported-by: Dmitry V. Levin <ldv@altlinux.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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.