Since "linux-user: fix use of SIGRTMIN" (6bc024e7), qemu removed
use of __SIGRTMAX except for in this QEMU_BUILD_BUG_ON assert.
Presumably, this check is to ensure that the loop in signal_table_init
from SIGRTMIN to SIGRTMAX falls within the bounds of
host_to_target_signal_table (_NSIG).
However, _NSIG is already defined to be the one larger than the
largest signal supported by the system (as specified in the upcoming
POSIX revision[0]), so the check is unnecessary.
musl libc does not define __SIGRTMAX, so removing this check fixes
one of the last remaining errors when building qemu.
[0] https://www.austingroupbugs.net/view.php?id=741
Signed-off-by: Michael Forney <mforney@mforney.org>
---
If you prefer, I can send an alternate patch to leave the
QEMU_BUILD_BUG_ON, but guard it by #ifdef __SIGRTMAX.
linux-user/signal.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 9016896dcd..6f62f2b528 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -38,7 +38,6 @@ static void host_signal_handler(int host_signum, siginfo_t *info,
* Signal number 0 is reserved for use as kill(pid, 0), to test whether
* a process exists without sending it a signal.
*/
-QEMU_BUILD_BUG_ON(__SIGRTMAX + 1 != _NSIG);
static uint8_t host_to_target_signal_table[_NSIG] = {
[SIGHUP] = TARGET_SIGHUP,
[SIGINT] = TARGET_SIGINT,
--
2.31.1
On 5/26/21 6:39 AM, Michael Forney wrote: > Since "linux-user: fix use of SIGRTMIN" (6bc024e7), qemu removed > use of __SIGRTMAX except for in this QEMU_BUILD_BUG_ON assert. > Presumably, this check is to ensure that the loop in signal_table_init > from SIGRTMIN to SIGRTMAX falls within the bounds of > host_to_target_signal_table (_NSIG). > > However, _NSIG is already defined to be the one larger than the > largest signal supported by the system (as specified in the upcoming > POSIX revision[0]), so the check is unnecessary. > > musl libc does not define __SIGRTMAX, so removing this check fixes > one of the last remaining errors when building qemu. > > [0] https://www.austingroupbugs.net/view.php?id=741 > > Signed-off-by: Michael Forney <mforney@mforney.org> > --- > If you prefer, I can send an alternate patch to leave the > QEMU_BUILD_BUG_ON, but guard it by #ifdef __SIGRTMAX. This looks safer, personally I prefer, but let's see what the maintainers prefer. > linux-user/signal.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/linux-user/signal.c b/linux-user/signal.c > index 9016896dcd..6f62f2b528 100644 > --- a/linux-user/signal.c > +++ b/linux-user/signal.c > @@ -38,7 +38,6 @@ static void host_signal_handler(int host_signum, siginfo_t *info, > * Signal number 0 is reserved for use as kill(pid, 0), to test whether > * a process exists without sending it a signal. > */ > -QEMU_BUILD_BUG_ON(__SIGRTMAX + 1 != _NSIG); > static uint8_t host_to_target_signal_table[_NSIG] = { > [SIGHUP] = TARGET_SIGHUP, > [SIGINT] = TARGET_SIGINT, >
Le 26/05/2021 à 19:16, Philippe Mathieu-Daudé a écrit : > On 5/26/21 6:39 AM, Michael Forney wrote: >> Since "linux-user: fix use of SIGRTMIN" (6bc024e7), qemu removed >> use of __SIGRTMAX except for in this QEMU_BUILD_BUG_ON assert. >> Presumably, this check is to ensure that the loop in signal_table_init >> from SIGRTMIN to SIGRTMAX falls within the bounds of >> host_to_target_signal_table (_NSIG). >> >> However, _NSIG is already defined to be the one larger than the >> largest signal supported by the system (as specified in the upcoming >> POSIX revision[0]), so the check is unnecessary. >> >> musl libc does not define __SIGRTMAX, so removing this check fixes >> one of the last remaining errors when building qemu. >> >> [0] https://www.austingroupbugs.net/view.php?id=741 >> >> Signed-off-by: Michael Forney <mforney@mforney.org> >> --- >> If you prefer, I can send an alternate patch to leave the >> QEMU_BUILD_BUG_ON, but guard it by #ifdef __SIGRTMAX. > > This looks safer, personally I prefer, but let's see what the > maintainers prefer. I agree, the reason of the check is explained in the comment above. I think it's safer to keep the QEMU_BUILD_BUG_ON(). In the past we had a confusion between _NSIG, NSIG and TARGET_NSIG. See 9fcff3a67f2b ("linux-user: fix TARGET_NSIG and _NSIG uses") Thanks, Laurent
Le 26/05/2021 à 06:39, Michael Forney a écrit : > Since "linux-user: fix use of SIGRTMIN" (6bc024e7), qemu removed > use of __SIGRTMAX except for in this QEMU_BUILD_BUG_ON assert. > Presumably, this check is to ensure that the loop in signal_table_init > from SIGRTMIN to SIGRTMAX falls within the bounds of > host_to_target_signal_table (_NSIG). > > However, _NSIG is already defined to be the one larger than the > largest signal supported by the system (as specified in the upcoming > POSIX revision[0]), so the check is unnecessary. > > musl libc does not define __SIGRTMAX, so removing this check fixes > one of the last remaining errors when building qemu. > > [0] https://www.austingroupbugs.net/view.php?id=741 > > Signed-off-by: Michael Forney <mforney@mforney.org> > --- > If you prefer, I can send an alternate patch to leave the > QEMU_BUILD_BUG_ON, but guard it by #ifdef __SIGRTMAX. > > linux-user/signal.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/linux-user/signal.c b/linux-user/signal.c > index 9016896dcd..6f62f2b528 100644 > --- a/linux-user/signal.c > +++ b/linux-user/signal.c > @@ -38,7 +38,6 @@ static void host_signal_handler(int host_signum, siginfo_t *info, > * Signal number 0 is reserved for use as kill(pid, 0), to test whether > * a process exists without sending it a signal. > */ > -QEMU_BUILD_BUG_ON(__SIGRTMAX + 1 != _NSIG); > static uint8_t host_to_target_signal_table[_NSIG] = { > [SIGHUP] = TARGET_SIGHUP, > [SIGINT] = TARGET_SIGINT, > Applied to my linux-user-for-6.1 branch. Thanks, Laurent
This check is to ensure that the loop in signal_table_init() from
SIGRTMIN to SIGRTMAX falls within the bounds of host_to_target_signal_table
(_NSIG). However, it is not critical, since _NSIG is already defined
to be the one larger than the largest signal supported by the system
(as specified in the upcoming POSIX revision[0]).
musl libc does not define __SIGRTMAX, so disabling this check when
it is missing fixes one of the last remaining errors when building
qemu.
[0] https://www.austingroupbugs.net/view.php?id=741
Signed-off-by: Michael Forney <mforney@mforney.org>
---
Changes since v2:
* Guard check by #ifdef __SIGRTMAX instead of removing it.
linux-user/signal.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 9016896dcd..0f19c59dee 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -38,7 +38,9 @@ static void host_signal_handler(int host_signum, siginfo_t *info,
* Signal number 0 is reserved for use as kill(pid, 0), to test whether
* a process exists without sending it a signal.
*/
+#ifdef __SIGRTMAX
QEMU_BUILD_BUG_ON(__SIGRTMAX + 1 != _NSIG);
+#endif
static uint8_t host_to_target_signal_table[_NSIG] = {
[SIGHUP] = TARGET_SIGHUP,
[SIGINT] = TARGET_SIGINT,
--
2.31.1
Le 26/05/2021 à 21:02, Michael Forney a écrit : > This check is to ensure that the loop in signal_table_init() from > SIGRTMIN to SIGRTMAX falls within the bounds of host_to_target_signal_table > (_NSIG). However, it is not critical, since _NSIG is already defined > to be the one larger than the largest signal supported by the system > (as specified in the upcoming POSIX revision[0]). > > musl libc does not define __SIGRTMAX, so disabling this check when > it is missing fixes one of the last remaining errors when building > qemu. > > [0] https://www.austingroupbugs.net/view.php?id=741 > > Signed-off-by: Michael Forney <mforney@mforney.org> > --- > Changes since v2: > * Guard check by #ifdef __SIGRTMAX instead of removing it. > > linux-user/signal.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/linux-user/signal.c b/linux-user/signal.c > index 9016896dcd..0f19c59dee 100644 > --- a/linux-user/signal.c > +++ b/linux-user/signal.c > @@ -38,7 +38,9 @@ static void host_signal_handler(int host_signum, siginfo_t *info, > * Signal number 0 is reserved for use as kill(pid, 0), to test whether > * a process exists without sending it a signal. > */ > +#ifdef __SIGRTMAX > QEMU_BUILD_BUG_ON(__SIGRTMAX + 1 != _NSIG); > +#endif > static uint8_t host_to_target_signal_table[_NSIG] = { > [SIGHUP] = TARGET_SIGHUP, > [SIGINT] = TARGET_SIGINT, > Reviewed-by: Laurent Vivier <laurent@vivier.eu>
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