r11 is a volatile register on PPC as per calling conventions.
The safe_syscall code uses it to check if the signal_pending
is set during the safe_syscall. When a syscall is interrupted
on return from signal handling, the r11 might be corrupted
before we retry the syscall leading to a crash. The registers
r0-r13 are not to be used here as they have
volatile/designated/reserved usages.
Change the code to use r14 which is non-volatile.
Use SP+16 which is a slot for LR, for save/restore of previous value
of r14. SP+16 can be used, as LR is preserved across the syscall.
Steps to reproduce:
On PPC host, issue `qemu-x86_64 /usr/bin/cc -E -`
Attempt Ctrl-C, the issue is reproduced.
Reference:
https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html#REGhttps://openpowerfoundation.org/wp-content/uploads/2016/03/ABI64BitOpenPOWERv1.1_16July2015_pub4.pdf
Signed-off-by: Shivaprasad G Bhat <sbhat@linux.vnet.ibm.com>
Tested-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <153301568965.30312.10498134581068746871.stgit@dhcp-9-109-246-16>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This unbreaks the testcase from
http://lists.nongnu.org/archive/html/qemu-arm/2018-01/msg00514.html
Thanks to Laurent Vivier for spotting the 7th one.
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Suggested-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <671eaa99f4e0bf3a58f76f9151f7cfa24662227f.1517565566.git.agx@sigxcpu.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
glibc used to have:
typedef struct ucontext { ... } ucontext_t;
glibc now has:
typedef struct ucontext_t { ... } ucontext_t;
(See https://sourceware.org/bugzilla/show_bug.cgi?id=21457
for detail and rationale for the glibc change)
However, QEMU used "struct ucontext" in declarations. This is a
private name and compatibility cannot be guaranteed. Switch to
only using the standardized type name.
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Message-id: 20170628204452.41230-1-raj.khem@gmail.com
Cc: Kamil Rytarowski <kamil@netbsd.org>
Cc: Riku Voipio <riku.voipio@iki.fi>
Cc: Laurent Vivier <laurent@vivier.eu>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[PMM: Rewrote commit message, based mostly on the one from
Nathaniel McCallum]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
The LT instruction was added in the extended immediate facility
introduced with the z9-109 processor.
Cc: Riku Voipio <riku.voipio@iki.fi>
Reported-by: Michael Tokarev <mjt@tls.msk.ru>
Fixes: c9bc3437a9
Suggested-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
These headers all use QEMU_HOSTDEP_H as header guard symbol. Reuse of
the same guard symbol in multiple headers is okay as long as they
cannot be included together.
Since we can avoid guard symbol reuse easily, do so: use guard symbol
$target_HOSTDEP_H for linux-user/host/$target/hostdep.h.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Clang insists that "cmp" is ambiguous with a memory destination,
requiring an explicit size suffix.
There was a true error in the use of .cfi_def_cfa_offset in the
epilogue, but changing to use the proper .cfi_adjust_cfa_offset
runs afoul of a clang bug wrt .cfi_restore_state. Better to
fold the two epilogues so that we don't trigger the bug.
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
[RV] Updated syscall argument comment to match code
Do what the comment says, test for signal_pending non-zero,
rather than the current code which tests for bit 0 non-zero.
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
In commit 4d330cee37 a new hostdep.h file was added, with the intent
that host architectures which needed one could provide it, and the
build system would automatically fall back to a generic version if
there was no version for the host architecture. Although this works,
it has a flaw: if a subsequent commit switches an architecture from
"uses generic/hostdep.h" to "uses its own hostdep.h" nothing in the
makefile dependencies notices this and so doing a rebuild without
a manual 'make clean' will fail.
So we drop the idea of having a 'generic' version in favour of
every architecture we support having its own hostdep.h, even if
it doesn't have anything in it. (There are only thirteen of these.)
If the dependency files claim that an object file depends on a
nonexistent file, our dependency system means that make will
rebuild the object file, and regenerate the dependencies in
the process. So moving between trees prior to this commit and
trees after this commit works without requiring a 'make clean'.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
Use cfi directives in the x86-64 safe_syscall to allow gdb to get
backtraces right from within it. (In particular this will be
quite a common situation if the user interrupts QEMU while it's
in a blocked safe-syscall: at the point of the syscall insn RBP
is in use for something else, and so gdb can't find the frame then
without assistance.)
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
If a signal is delivered immediately before a blocking system call the
handler will only be called after the system call returns, which may be a
long time later or never.
This is fixed by using a function (safe_syscall) that checks if a guest
signal is pending prior to making a system call, and if so does not call the
system call and returns -TARGET_ERESTARTSYS. If a signal is received between
the check and the system call host_signal_handler() rewinds execution to
before the check. This rewinding has the effect of closing the race window
so that safe_syscall will reliably either (a) go into the host syscall
with no unprocessed guest signals pending or or (b) return
-TARGET_ERESTARTSYS so that the caller can deal with the signals.
Implementing this requires a per-host-architecture assembly language
fragment.
This will also resolve the mishandling of the SA_RESTART flag where
we would restart a host system call and not call the guest signal handler
until the syscall finally completed -- syscall restarting now always
happens at the guest syscall level so the guest signal handler will run.
(The host syscall will never be restarted because if the host kernel
rewinds the PC to point at the syscall insn for a restart then our
host_signal_handler() will see this and arrange the guest PC rewind.)
This commit contains the infrastructure for implementing safe_syscall
and the assembly language fragment for x86-64, but does not change any
syscalls to use it.
Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
Message-id: 1441497448-32489-14-git-send-email-T.E.Baldwin99@members.leeds.ac.uk
[PMM:
* Avoid having an architecture if-ladder in configure by putting
linux-user/host/$(ARCH) on the include path and including
safe-syscall.inc.S from it
* Avoid ifdef ladder in signal.c by creating new hostdep.h to hold
host-architecture-specific things
* Added copyright/license header to safe-syscall.inc.S
* Rewrote commit message
* Added comments to safe-syscall.inc.S
* Changed calling convention of safe_syscall() to match syscall()
(returns -1 and host error in errno on failure)
* Added a long comment in qemu.h about how to use safe_syscall()
to implement guest syscalls.
]
RV: squashed Peters "fixup! linux-user: compile on non-x86-64 hosts"
patch
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Shivaprasad G Bhat
Guido Günther
Khem Raj
Richard Henderson
Markus Armbruster
Peter Maydell
Timothy E Baldwin