All instances of rewind_if_in_safe_syscall are the same, differing only
in how the instruction point is fetched from the ucontext and the size
of the registers. Use host_signal_pc and new host_signal_set_pc
interfaces to fetch the pointer to the PC and adjust if needed. Delete
all the old copies of rewind_if_in_safe_syscall.
Acked-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20211113045603.60391-3-imp@bsdimp.com>
[rth: include safe-syscall.h, simplify ifdefs]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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>
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>
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>
Warner Losh
Khem Raj
Markus Armbruster
Timothy E Baldwin