This is a really cool idea. It will indeed work for alarms, because
the application-specific alarm function will call the
application-specific kill() function which will run the application's
choice of handler.
However, I think it will not really work in places where unduplicated
OSv code calls kill() or related functions. For example:
1. In drivers/line-discipline.cc, we call kill(0, SIGINT). This will
call the main kill and the main handler - not the application's, so
the application's attempt to catch SIGINT will simply not work, even
if there's just one application (if started with the signal
virtualization flag). Arguably this is not an important problem - an
application cannot hope to catch SIGINT in this case, so it's ok that
it doesn't.
2. When we have a page fault, division by zero, and similar
exceptions, code in exceptions.cc and core/mmu.cc calls the functions
generate_signal() and handle_mmap_fault() which are (to make a long
story short) specialized versions of kill. Although both these
functions are in signal.cc and are duplicated for each application,
it doesn't help because the OSv kernel calls them, so it uses the
version in the OSv kernel, not the one in the application. This might
be a problem: If Java, for example, needs to capture SIGSEGV to do
something (not just for error reporting but for actual correct
operation), then its signal handler will be ignored. Did you test
Java with this patch?
One way we can solve this problem is perhaps for the
generate_signal() function to start by looking for a function by this
name in the current application (the one the current thread belongs
to) and if we find one which is not the one currently running, we run
the one from the application instead. This will obviously slow down
this function, but I hope it's not very frequently used (although
it's worth checking how often some Java program runs it, we can
easily add a tracepoint if we don't already have one, and count it
with scripts/freq.py).
Maybe there are other ways to solve this. Or maybe we should just
start by having this feature only "partially" work as it does now,
for only some applications?
.
--
Nadav Har'El
[email protected] <mailto:[email protected]>
On Wed, Mar 8, 2017 at 9:22 AM, Justin Cinkelj
<[email protected] <mailto:[email protected]>> wrote:
Before patch, netperf netserver.so and netperf.so could not be run in
the same VM. The netserver reports "error starting alarm timer,
ret 3 errno 28".
The patch make alarm (and also signals) per namespace specific,
in the
wat as environ was made per namespace specific in
e93af8d3622ba1cf491ba12c780f05bb447de8ac and
1d3645b6c1a119ea34e1a3dca6ae814d4902905f.
Signed-off-by: Justin Cinkelj <[email protected]
<mailto:[email protected]>>
---
Makefile | 9 ++++++++-
core/app.cc | 10 ++++++++++
include/osv/app.hh | 2 ++
usr.manifest.skel | 1 +
4 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index 6846c5e..d982864 100644
--- a/Makefile
+++ b/Makefile
@@ -926,6 +926,7 @@ libc =
musl =
environ_libc =
environ_musl =
+signal_libc =
ifeq ($(arch),x64)
musl_arch = x86_64
@@ -995,6 +996,8 @@ environ_musl += env/putenv.c
environ_musl += env/setenv.c
environ_musl += env/unsetenv.c
+signal_libc += signal.cc
+
musl += ctype/__ctype_b_loc.o
musl += errno/strerror.o
@@ -1830,10 +1833,14 @@ $(out)/bsd/%.o: COMMON += -DSMP
-D'__FBSDID(__str__)=extern int __bogus__'
environ_sources = $(addprefix libc/, $(environ_libc))
environ_sources += $(addprefix musl/src/, $(environ_musl))
+signal_sources = $(addprefix libc/, $(signal_libc))
$(out)/libenviron.so: $(environ_sources)
$(makedir)
$(call quiet, $(CC) $(CFLAGS) -shared -o
$(out)/libenviron.so $(environ_sources), CC libenviron.so)
+$(out)/libsignal.so: $(signal_sources)
+ $(makedir)
+ $(call quiet, $(CXX) $(CXXFLAGS) -shared -o
$(out)/libsignal.so $(signal_sources), CXX libsignal.so)
bootfs_manifest ?= bootfs.manifest.skel
@@ -1847,7 +1854,7 @@ $(bootfs_manifest_dep): phony
fi
$(out)/bootfs.bin: scripts/mkbootfs.py $(bootfs_manifest)
$(bootfs_manifest_dep) $(tools:%=$(out)/%) \
- $(out)/zpool.so $(out)/zfs.so $(out)/libenviron.so
+ $(out)/zpool.so $(out)/zfs.so
$(out)/libenviron.so $(out)/libsignal.so
$(call quiet, olddir=`pwd`; cd $(out);
$$olddir/scripts/mkbootfs.py -o bootfs.bin -d bootfs.bin.d -m
$$olddir/$(bootfs_manifest) \
-D jdkbase=$(jdkbase) -D gccbase=$(gccbase) -D \
glibcbase=$(glibcbase) -D miscbase=$(miscbase),
MKBOOTFS $@)
diff --git a/core/app.cc b/core/app.cc
index d623a61..b800522 100644
--- a/core/app.cc
+++ b/core/app.cc
@@ -161,6 +161,7 @@ application::application(const std::string&
command,
if (new_program) {
this->new_program();
clone_osv_environ();
+ clone_osv_signal();
current_program = _program.get();
} else {
// Do it in a separate branch because
elf::get_program() would not
@@ -449,6 +450,15 @@ elf::program *application::program() {
}
+void application::clone_osv_signal()
+{
+ _libsignal = _program->get_library("libsignal.so");
+ if (!_libsignal) {
+ abort("could not load libsignal.so\n");
+ return;
+ }
+}
+
void application::clone_osv_environ()
{
_libenviron = _program->get_library("libenviron.so");
diff --git a/include/osv/app.hh b/include/osv/app.hh
index 83e017e..d301551 100644
--- a/include/osv/app.hh
+++ b/include/osv/app.hh
@@ -185,6 +185,7 @@ public:
elf::program *program();
private:
void new_program();
+ void clone_osv_signal();
void clone_osv_environ();
void set_environ(const std::string &key, const std::string
&value,
bool new_program);
@@ -213,6 +214,7 @@ private:
mutex _termination_mutex;
std::shared_ptr<elf::object> _lib;
std::shared_ptr<elf::object> _libenviron;
+ std::shared_ptr<elf::object> _libsignal;
main_func_t* _main;
void (*_entry_point)();
static app_registry apps;
diff --git a/usr.manifest.skel b/usr.manifest.skel
index 583bdfe..73f58c1 100644
--- a/usr.manifest.skel
+++ b/usr.manifest.skel
@@ -1,5 +1,6 @@
[manifest]
/libenviron.so: libenviron.so
+/libsignal.so: libsignal.so
/zpool.so: zpool.so
/libzfs.so: libzfs.so
/libuutil.so: libuutil.so
--
2.9.3
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