* [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX
@ 2021-05-26 4:39 Michael Forney
2021-05-26 17:16 ` Philippe Mathieu-Daudé
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Michael Forney @ 2021-05-26 4:39 UTC (permalink / raw)
To: Laurent Vivier; +Cc: qemu-devel
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
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX
2021-05-26 4:39 [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX Michael Forney
@ 2021-05-26 17:16 ` Philippe Mathieu-Daudé
2021-05-26 18:36 ` Laurent Vivier
2021-05-26 19:02 ` [PATCH v2] linux-user: Disable static assert involving __SIGRTMAX if it is missing Michael Forney
2021-06-15 6:38 ` [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX Laurent Vivier
2 siblings, 1 reply; 6+ messages in thread
From: Philippe Mathieu-Daudé @ 2021-05-26 17:16 UTC (permalink / raw)
To: Michael Forney, Laurent Vivier; +Cc: qemu-devel
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,
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX
2021-05-26 17:16 ` Philippe Mathieu-Daudé
@ 2021-05-26 18:36 ` Laurent Vivier
0 siblings, 0 replies; 6+ messages in thread
From: Laurent Vivier @ 2021-05-26 18:36 UTC (permalink / raw)
To: Philippe Mathieu-Daudé, Michael Forney; +Cc: qemu-devel
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
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2] linux-user: Disable static assert involving __SIGRTMAX if it is missing
2021-05-26 4:39 [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX Michael Forney
2021-05-26 17:16 ` Philippe Mathieu-Daudé
@ 2021-05-26 19:02 ` Michael Forney
2021-05-26 20:02 ` Laurent Vivier
2021-06-15 6:38 ` [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX Laurent Vivier
2 siblings, 1 reply; 6+ messages in thread
From: Michael Forney @ 2021-05-26 19:02 UTC (permalink / raw)
To: Laurent Vivier; +Cc: qemu-devel
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
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2] linux-user: Disable static assert involving __SIGRTMAX if it is missing
2021-05-26 19:02 ` [PATCH v2] linux-user: Disable static assert involving __SIGRTMAX if it is missing Michael Forney
@ 2021-05-26 20:02 ` Laurent Vivier
0 siblings, 0 replies; 6+ messages in thread
From: Laurent Vivier @ 2021-05-26 20:02 UTC (permalink / raw)
To: Michael Forney; +Cc: qemu-devel
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>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX
2021-05-26 4:39 [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX Michael Forney
2021-05-26 17:16 ` Philippe Mathieu-Daudé
2021-05-26 19:02 ` [PATCH v2] linux-user: Disable static assert involving __SIGRTMAX if it is missing Michael Forney
@ 2021-06-15 6:38 ` Laurent Vivier
2 siblings, 0 replies; 6+ messages in thread
From: Laurent Vivier @ 2021-06-15 6:38 UTC (permalink / raw)
To: Michael Forney; +Cc: qemu-devel
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
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-06-15 6:39 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2021-05-26 4:39 [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX Michael Forney
2021-05-26 17:16 ` Philippe Mathieu-Daudé
2021-05-26 18:36 ` Laurent Vivier
2021-05-26 19:02 ` [PATCH v2] linux-user: Disable static assert involving __SIGRTMAX if it is missing Michael Forney
2021-05-26 20:02 ` Laurent Vivier
2021-06-15 6:38 ` [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX Laurent Vivier
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