| Message ID | 20190725131645.19501-1-peter.maydell@linaro.org |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [for-4.1] linux-user: Make sigaltstack stacks per-thread | expand |
Le 25/07/2019 à 15:16, Peter Maydell a écrit : > The alternate signal stack set up by the sigaltstack syscall is > supposed to be per-thread. We were incorrectly implementing it as > process-wide. This causes problems for guest binaries that rely on > this. Notably the Go runtime does, and so we were seeing crashes > caused by races where two guest threads might incorrectly both > execute on the same stack simultaneously. > > Replace the global target_sigaltstack_used with a field > sigaltstack_used in the TaskState, and make all the references to the > old global instead get a pointer to the TaskState and use the field. > > Fixes: https://bugs.launchpad.net/qemu/+bug/1696773 > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > I've marked this as "for-4.1" but it is quite late in the release > cycle and I think this could use more testing than I have given it... It looks good. I'm going to test it with LTP on all the targets I have. I will test the go program too. Thanks, Laurent > > Thanks are due to: > * the original bug reporter, for providing a nice simple test case > * rr, for allowing me to capture and forensically examine a single > example of the failure > * the Go project for having a good clear HACKING.md that explained > their stack usage and mentioned specifically that signal stacks > are per-thread (per-M, in their terms) > * a colleague, for prodding me into actually spending the necessary > two days grovelling through gdb sessions and logs to figure out > what was actually going wrong > --- > linux-user/qemu.h | 2 ++ > linux-user/signal-common.h | 1 - > linux-user/hppa/signal.c | 3 ++- > linux-user/main.c | 5 +++++ > linux-user/signal.c | 35 +++++++++++++++++++---------------- > 5 files changed, 28 insertions(+), 18 deletions(-) > > diff --git a/linux-user/qemu.h b/linux-user/qemu.h > index 4258e4162d2..aac03346270 100644 > --- a/linux-user/qemu.h > +++ b/linux-user/qemu.h > @@ -151,6 +151,8 @@ typedef struct TaskState { > */ > int signal_pending; > > + /* This thread's sigaltstack, if it has one */ > + struct target_sigaltstack sigaltstack_used; > } __attribute__((aligned(16))) TaskState; > > extern char *exec_path; > diff --git a/linux-user/signal-common.h b/linux-user/signal-common.h > index 51030a93069..1df1068552f 100644 > --- a/linux-user/signal-common.h > +++ b/linux-user/signal-common.h > @@ -19,7 +19,6 @@ > > #ifndef SIGNAL_COMMON_H > #define SIGNAL_COMMON_H > -extern struct target_sigaltstack target_sigaltstack_used; > > int on_sig_stack(unsigned long sp); > int sas_ss_flags(unsigned long sp); > diff --git a/linux-user/hppa/signal.c b/linux-user/hppa/signal.c > index b6927ee6735..d1a58feeb36 100644 > --- a/linux-user/hppa/signal.c > +++ b/linux-user/hppa/signal.c > @@ -111,10 +111,11 @@ void setup_rt_frame(int sig, struct target_sigaction *ka, > abi_ulong frame_addr, sp, haddr; > struct target_rt_sigframe *frame; > int i; > + TaskState *ts = (TaskState *)thread_cpu->opaque; > > sp = get_sp_from_cpustate(env); > if ((ka->sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp)) { > - sp = (target_sigaltstack_used.ss_sp + 0x7f) & ~0x3f; > + sp = (ts->sigaltstack_used.ss_sp + 0x7f) & ~0x3f; > } > frame_addr = QEMU_ALIGN_UP(sp, 64); > sp = frame_addr + PARISC_RT_SIGFRAME_SIZE32; > diff --git a/linux-user/main.c b/linux-user/main.c > index a59ae9439de..8ffc5251955 100644 > --- a/linux-user/main.c > +++ b/linux-user/main.c > @@ -180,6 +180,11 @@ void stop_all_tasks(void) > void init_task_state(TaskState *ts) > { > ts->used = 1; > + ts->sigaltstack_used = (struct target_sigaltstack) { > + .ss_sp = 0, > + .ss_size = 0, > + .ss_flags = TARGET_SS_DISABLE, > + }; > } > > CPUArchState *cpu_copy(CPUArchState *env) > diff --git a/linux-user/signal.c b/linux-user/signal.c > index 5cd237834d9..5ca6d62b15d 100644 > --- a/linux-user/signal.c > +++ b/linux-user/signal.c > @@ -25,12 +25,6 @@ > #include "trace.h" > #include "signal-common.h" > > -struct target_sigaltstack target_sigaltstack_used = { > - .ss_sp = 0, > - .ss_size = 0, > - .ss_flags = TARGET_SS_DISABLE, > -}; > - > static struct target_sigaction sigact_table[TARGET_NSIG]; > > static void host_signal_handler(int host_signum, siginfo_t *info, > @@ -251,13 +245,17 @@ void set_sigmask(const sigset_t *set) > > int on_sig_stack(unsigned long sp) > { > - return (sp - target_sigaltstack_used.ss_sp > - < target_sigaltstack_used.ss_size); > + TaskState *ts = (TaskState *)thread_cpu->opaque; > + > + return (sp - ts->sigaltstack_used.ss_sp > + < ts->sigaltstack_used.ss_size); > } > > int sas_ss_flags(unsigned long sp) > { > - return (target_sigaltstack_used.ss_size == 0 ? SS_DISABLE > + TaskState *ts = (TaskState *)thread_cpu->opaque; > + > + return (ts->sigaltstack_used.ss_size == 0 ? SS_DISABLE > : on_sig_stack(sp) ? SS_ONSTACK : 0); > } > > @@ -266,17 +264,21 @@ abi_ulong target_sigsp(abi_ulong sp, struct target_sigaction *ka) > /* > * This is the X/Open sanctioned signal stack switching. > */ > + TaskState *ts = (TaskState *)thread_cpu->opaque; > + > if ((ka->sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp)) { > - return target_sigaltstack_used.ss_sp + target_sigaltstack_used.ss_size; > + return ts->sigaltstack_used.ss_sp + ts->sigaltstack_used.ss_size; > } > return sp; > } > > void target_save_altstack(target_stack_t *uss, CPUArchState *env) > { > - __put_user(target_sigaltstack_used.ss_sp, &uss->ss_sp); > + TaskState *ts = (TaskState *)thread_cpu->opaque; > + > + __put_user(ts->sigaltstack_used.ss_sp, &uss->ss_sp); > __put_user(sas_ss_flags(get_sp_from_cpustate(env)), &uss->ss_flags); > - __put_user(target_sigaltstack_used.ss_size, &uss->ss_size); > + __put_user(ts->sigaltstack_used.ss_size, &uss->ss_size); > } > > /* siginfo conversion */ > @@ -708,12 +710,13 @@ abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp) > { > int ret; > struct target_sigaltstack oss; > + TaskState *ts = (TaskState *)thread_cpu->opaque; > > /* XXX: test errors */ > if(uoss_addr) > { > - __put_user(target_sigaltstack_used.ss_sp, &oss.ss_sp); > - __put_user(target_sigaltstack_used.ss_size, &oss.ss_size); > + __put_user(ts->sigaltstack_used.ss_sp, &oss.ss_sp); > + __put_user(ts->sigaltstack_used.ss_size, &oss.ss_size); > __put_user(sas_ss_flags(sp), &oss.ss_flags); > } > > @@ -760,8 +763,8 @@ abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp) > } > } > > - target_sigaltstack_used.ss_sp = ss.ss_sp; > - target_sigaltstack_used.ss_size = ss.ss_size; > + ts->sigaltstack_used.ss_sp = ss.ss_sp; > + ts->sigaltstack_used.ss_size = ss.ss_size; > } > > if (uoss_addr) { >
On 7/25/19 6:16 AM, Peter Maydell wrote: > The alternate signal stack set up by the sigaltstack syscall is > supposed to be per-thread. We were incorrectly implementing it as > process-wide. This causes problems for guest binaries that rely on > this. Notably the Go runtime does, and so we were seeing crashes > caused by races where two guest threads might incorrectly both > execute on the same stack simultaneously. > > Replace the global target_sigaltstack_used with a field > sigaltstack_used in the TaskState, and make all the references to the > old global instead get a pointer to the TaskState and use the field. > > Fixes: https://bugs.launchpad.net/qemu/+bug/1696773 > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
Le 25/07/2019 à 15:16, Peter Maydell a écrit : > The alternate signal stack set up by the sigaltstack syscall is > supposed to be per-thread. We were incorrectly implementing it as > process-wide. This causes problems for guest binaries that rely on > this. Notably the Go runtime does, and so we were seeing crashes > caused by races where two guest threads might incorrectly both > execute on the same stack simultaneously. > > Replace the global target_sigaltstack_used with a field > sigaltstack_used in the TaskState, and make all the references to the > old global instead get a pointer to the TaskState and use the field. > > Fixes: https://bugs.launchpad.net/qemu/+bug/1696773 > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > I've marked this as "for-4.1" but it is quite late in the release > cycle and I think this could use more testing than I have given it... > > Thanks are due to: > * the original bug reporter, for providing a nice simple test case > * rr, for allowing me to capture and forensically examine a single > example of the failure > * the Go project for having a good clear HACKING.md that explained > their stack usage and mentioned specifically that signal stacks > are per-thread (per-M, in their terms) > * a colleague, for prodding me into actually spending the necessary > two days grovelling through gdb sessions and logs to figure out > what was actually going wrong > --- > linux-user/qemu.h | 2 ++ > linux-user/signal-common.h | 1 - > linux-user/hppa/signal.c | 3 ++- > linux-user/main.c | 5 +++++ > linux-user/signal.c | 35 +++++++++++++++++++---------------- > 5 files changed, 28 insertions(+), 18 deletions(-) Tested-by: Laurent Vivier <laurent@vivier.eu> Reviewed-by: Laurent Vivier <laurent@vivier.eu> This patch seems also to fix failure of LTP test waitpid02. Thanks, Laurent
On Fri, 26 Jul 2019 at 18:17, Laurent Vivier <laurent@vivier.eu> wrote: > Tested-by: Laurent Vivier <laurent@vivier.eu> > Reviewed-by: Laurent Vivier <laurent@vivier.eu> > > This patch seems also to fix failure of LTP test waitpid02. Well, that's a bonus :-) Could you submit a pullreq in time for rc3 (Tuesday), please? thanks -- PMM
diff --git a/linux-user/qemu.h b/linux-user/qemu.h index 4258e4162d2..aac03346270 100644 --- a/linux-user/qemu.h +++ b/linux-user/qemu.h @@ -151,6 +151,8 @@ typedef struct TaskState { */ int signal_pending; + /* This thread's sigaltstack, if it has one */ + struct target_sigaltstack sigaltstack_used; } __attribute__((aligned(16))) TaskState; extern char *exec_path; diff --git a/linux-user/signal-common.h b/linux-user/signal-common.h index 51030a93069..1df1068552f 100644 --- a/linux-user/signal-common.h +++ b/linux-user/signal-common.h @@ -19,7 +19,6 @@ #ifndef SIGNAL_COMMON_H #define SIGNAL_COMMON_H -extern struct target_sigaltstack target_sigaltstack_used; int on_sig_stack(unsigned long sp); int sas_ss_flags(unsigned long sp); diff --git a/linux-user/hppa/signal.c b/linux-user/hppa/signal.c index b6927ee6735..d1a58feeb36 100644 --- a/linux-user/hppa/signal.c +++ b/linux-user/hppa/signal.c @@ -111,10 +111,11 @@ void setup_rt_frame(int sig, struct target_sigaction *ka, abi_ulong frame_addr, sp, haddr; struct target_rt_sigframe *frame; int i; + TaskState *ts = (TaskState *)thread_cpu->opaque; sp = get_sp_from_cpustate(env); if ((ka->sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp)) { - sp = (target_sigaltstack_used.ss_sp + 0x7f) & ~0x3f; + sp = (ts->sigaltstack_used.ss_sp + 0x7f) & ~0x3f; } frame_addr = QEMU_ALIGN_UP(sp, 64); sp = frame_addr + PARISC_RT_SIGFRAME_SIZE32; diff --git a/linux-user/main.c b/linux-user/main.c index a59ae9439de..8ffc5251955 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -180,6 +180,11 @@ void stop_all_tasks(void) void init_task_state(TaskState *ts) { ts->used = 1; + ts->sigaltstack_used = (struct target_sigaltstack) { + .ss_sp = 0, + .ss_size = 0, + .ss_flags = TARGET_SS_DISABLE, + }; } CPUArchState *cpu_copy(CPUArchState *env) diff --git a/linux-user/signal.c b/linux-user/signal.c index 5cd237834d9..5ca6d62b15d 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -25,12 +25,6 @@ #include "trace.h" #include "signal-common.h" -struct target_sigaltstack target_sigaltstack_used = { - .ss_sp = 0, - .ss_size = 0, - .ss_flags = TARGET_SS_DISABLE, -}; - static struct target_sigaction sigact_table[TARGET_NSIG]; static void host_signal_handler(int host_signum, siginfo_t *info, @@ -251,13 +245,17 @@ void set_sigmask(const sigset_t *set) int on_sig_stack(unsigned long sp) { - return (sp - target_sigaltstack_used.ss_sp - < target_sigaltstack_used.ss_size); + TaskState *ts = (TaskState *)thread_cpu->opaque; + + return (sp - ts->sigaltstack_used.ss_sp + < ts->sigaltstack_used.ss_size); } int sas_ss_flags(unsigned long sp) { - return (target_sigaltstack_used.ss_size == 0 ? SS_DISABLE + TaskState *ts = (TaskState *)thread_cpu->opaque; + + return (ts->sigaltstack_used.ss_size == 0 ? SS_DISABLE : on_sig_stack(sp) ? SS_ONSTACK : 0); } @@ -266,17 +264,21 @@ abi_ulong target_sigsp(abi_ulong sp, struct target_sigaction *ka) /* * This is the X/Open sanctioned signal stack switching. */ + TaskState *ts = (TaskState *)thread_cpu->opaque; + if ((ka->sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp)) { - return target_sigaltstack_used.ss_sp + target_sigaltstack_used.ss_size; + return ts->sigaltstack_used.ss_sp + ts->sigaltstack_used.ss_size; } return sp; } void target_save_altstack(target_stack_t *uss, CPUArchState *env) { - __put_user(target_sigaltstack_used.ss_sp, &uss->ss_sp); + TaskState *ts = (TaskState *)thread_cpu->opaque; + + __put_user(ts->sigaltstack_used.ss_sp, &uss->ss_sp); __put_user(sas_ss_flags(get_sp_from_cpustate(env)), &uss->ss_flags); - __put_user(target_sigaltstack_used.ss_size, &uss->ss_size); + __put_user(ts->sigaltstack_used.ss_size, &uss->ss_size); } /* siginfo conversion */ @@ -708,12 +710,13 @@ abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp) { int ret; struct target_sigaltstack oss; + TaskState *ts = (TaskState *)thread_cpu->opaque; /* XXX: test errors */ if(uoss_addr) { - __put_user(target_sigaltstack_used.ss_sp, &oss.ss_sp); - __put_user(target_sigaltstack_used.ss_size, &oss.ss_size); + __put_user(ts->sigaltstack_used.ss_sp, &oss.ss_sp); + __put_user(ts->sigaltstack_used.ss_size, &oss.ss_size); __put_user(sas_ss_flags(sp), &oss.ss_flags); } @@ -760,8 +763,8 @@ abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp) } } - target_sigaltstack_used.ss_sp = ss.ss_sp; - target_sigaltstack_used.ss_size = ss.ss_size; + ts->sigaltstack_used.ss_sp = ss.ss_sp; + ts->sigaltstack_used.ss_size = ss.ss_size; } if (uoss_addr) {
The alternate signal stack set up by the sigaltstack syscall is supposed to be per-thread. We were incorrectly implementing it as process-wide. This causes problems for guest binaries that rely on this. Notably the Go runtime does, and so we were seeing crashes caused by races where two guest threads might incorrectly both execute on the same stack simultaneously. Replace the global target_sigaltstack_used with a field sigaltstack_used in the TaskState, and make all the references to the old global instead get a pointer to the TaskState and use the field. Fixes: https://bugs.launchpad.net/qemu/+bug/1696773 Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- I've marked this as "for-4.1" but it is quite late in the release cycle and I think this could use more testing than I have given it... Thanks are due to: * the original bug reporter, for providing a nice simple test case * rr, for allowing me to capture and forensically examine a single example of the failure * the Go project for having a good clear HACKING.md that explained their stack usage and mentioned specifically that signal stacks are per-thread (per-M, in their terms) * a colleague, for prodding me into actually spending the necessary two days grovelling through gdb sessions and logs to figure out what was actually going wrong --- linux-user/qemu.h | 2 ++ linux-user/signal-common.h | 1 - linux-user/hppa/signal.c | 3 ++- linux-user/main.c | 5 +++++ linux-user/signal.c | 35 +++++++++++++++++++---------------- 5 files changed, 28 insertions(+), 18 deletions(-) -- 2.20.1