[PATCH for-7.1? 0/2] Re-enable ppc32 as a linux-user host

[PATCH for-7.1? 0/2] Re-enable ppc32 as a linux-user host

[Richard Henderson]

This is, technically, a regression from 6.2, so it's not
implausible to apply before rc1.  Thoughts?


r~


Richard Henderson (2):
  common-user/host/ppc: Implement safe-syscall.inc.S
  linux-user: Implment host/ppc/host-signal.h

 linux-user/include/host/ppc/host-signal.h |  39 ++++++++
 common-user/host/ppc/safe-syscall.inc.S   | 107 ++++++++++++++++++++++
 2 files changed, 146 insertions(+)
 create mode 100644 linux-user/include/host/ppc/host-signal.h
 create mode 100644 common-user/host/ppc/safe-syscall.inc.S

-- 
2.34.1

[PATCH 1/2] common-user/host/ppc: Implement safe-syscall.inc.S

[Richard Henderson]

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 common-user/host/ppc/safe-syscall.inc.S | 107 ++++++++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 common-user/host/ppc/safe-syscall.inc.S

diff --git a/common-user/host/ppc/safe-syscall.inc.S b/common-user/host/ppc/safe-syscall.inc.S
new file mode 100644
index 0000000000..0851f6c0b8
--- /dev/null
+++ b/common-user/host/ppc/safe-syscall.inc.S
@@ -0,0 +1,107 @@
+/*
+ * safe-syscall.inc.S : host-specific assembly fragment
+ * to handle signals occurring at the same time as system calls.
+ * This is intended to be included by common-user/safe-syscall.S
+ *
+ * Copyright (C) 2022 Linaro, Ltd.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+/*
+ * Standardize on the _CALL_FOO symbols used by GCC:
+ * Apple XCode does not define _CALL_DARWIN.
+ * Clang defines _CALL_ELF (64-bit) but not _CALL_SYSV (32-bit).
+ */
+#if !defined(_CALL_SYSV) && \
+    !defined(_CALL_DARWIN) && \
+    !defined(_CALL_AIX) && \
+    !defined(_CALL_ELF)
+# if defined(__APPLE__)
+#  define _CALL_DARWIN
+# elif defined(__ELF__) && TCG_TARGET_REG_BITS == 32
+#  define _CALL_SYSV
+# else
+#  error "Unknown ABI"
+# endif
+#endif 
+
+#ifndef _CALL_SYSV
+# error "Unsupported ABI"
+#endif
+
+
+        .global safe_syscall_base
+        .global safe_syscall_start
+        .global safe_syscall_end
+        .type   safe_syscall_base, @function
+
+        .text
+
+        /*
+         * This is the entry point for making a system call. The calling
+         * convention here is that of a C varargs function with the
+         * first argument an 'int *' to the signal_pending flag, the
+         * second one the system call number (as a 'long'), and all further
+         * arguments being syscall arguments (also 'long').
+         */
+safe_syscall_base:
+        .cfi_startproc
+        stwu    1, -8(1)
+        .cfi_def_cfa_offset 8
+        stw     30, 4(1)
+        .cfi_offset 30, -4
+
+        /*
+         * We enter with r3 == &signal_pending
+         *               r4 == syscall number
+         *               r5 ... r10 == syscall arguments
+         *               and return the result in r3
+         * and the syscall instruction needs
+         *               r0 == syscall number
+         *               r3 ... r8 == syscall arguments
+         *               and returns the result in r3
+         * Shuffle everything around appropriately.
+         */
+        mr      30, 3           /* signal_pending */
+        mr      0, 4            /* syscall number */
+        mr      3, 5            /* syscall arguments */
+        mr      4, 6
+        mr      5, 7
+        mr      6, 8
+        mr      7, 9
+        mr      8, 10
+
+        /*
+         * This next sequence of code works in conjunction with the
+         * rewind_if_safe_syscall_function(). If a signal is taken
+         * and the interrupted PC is anywhere between 'safe_syscall_start'
+         * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
+         * The code sequence must therefore be able to cope with this, and
+         * the syscall instruction must be the final one in the sequence.
+         */
+safe_syscall_start:
+        /* if signal_pending is non-zero, don't do the call */
+        lwz     12, 0(30)
+        cmpwi   0, 12, 0
+        bne-    2f
+        sc
+safe_syscall_end:
+        /* code path when we did execute the syscall */
+        lwz     30, 4(1)        /* restore r30 */
+        addi    1, 1, 8         /* restore stack */
+        .cfi_restore 30
+        .cfi_def_cfa_offset 0
+        bnslr+                  /* return on success */
+        b       safe_syscall_set_errno_tail
+
+        /* code path when we didn't execute the syscall */
+2:      lwz     30, 4(1)
+        addi    1, 1, 8
+        addi    3, 0, QEMU_ERESTARTSYS
+        b       safe_syscall_set_errno_tail
+
+        .cfi_endproc
+
+        .size   safe_syscall_base, .-safe_syscall_base
-- 
2.34.1

[PATCH 2/2] linux-user: Implment host/ppc/host-signal.h

[Richard Henderson]

This commit re-enables ppc32 as a linux-user host,
as existance of the directory is noted by configure.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1097
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/include/host/ppc/host-signal.h | 39 +++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 linux-user/include/host/ppc/host-signal.h

diff --git a/linux-user/include/host/ppc/host-signal.h b/linux-user/include/host/ppc/host-signal.h
new file mode 100644
index 0000000000..de25c803f5
--- /dev/null
+++ b/linux-user/include/host/ppc/host-signal.h
@@ -0,0 +1,39 @@
+/*
+ * host-signal.h: signal info dependent on the host architecture
+ *
+ * Copyright (c) 2022 Linaro Ltd.
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef PPC_HOST_SIGNAL_H
+#define PPC_HOST_SIGNAL_H
+
+#include <asm/ptrace.h>
+
+/* The third argument to a SA_SIGINFO handler is ucontext_t. */
+typedef ucontext_t host_sigcontext;
+
+static inline uintptr_t host_signal_pc(host_sigcontext *uc)
+{
+    return uc->uc_mcontext.regs->nip;
+}
+
+static inline void host_signal_set_pc(host_sigcontext *uc, uintptr_t pc)
+{
+    uc->uc_mcontext.regs->nip = pc;
+}
+
+static inline void *host_signal_mask(host_sigcontext *uc)
+{
+    return &uc->uc_sigmask;
+}
+
+static inline bool host_signal_write(siginfo_t *info, host_sigcontext *uc)
+{
+    return uc->uc_mcontext.regs->trap != 0x400
+        && (uc->uc_mcontext.regs->dsisr & 0x02000000);
+}
+
+#endif
-- 
2.34.1

Re: [PATCH for-7.1? 0/2] Re-enable ppc32 as a linux-user host

[Daniel Henrique Barboza]

On 7/29/22 14:21, Richard Henderson wrote:
> This is, technically, a regression from 6.2, so it's not
> implausible to apply before rc1.  Thoughts?


In gitlab #1097 the author comments that:

https://gitlab.com/qemu-project/qemu/-/issues/1097#note_1044810483

"there are several distributions still available on 32-bit powerpc, e.g.
Adélie Linux, for now still Void Linux, afaik Debian and OpenSUSE also
still build packages"

I checked these claims. Latest version OpenSuse LEAP doesn't support
ppc32 bits:

https://get.opensuse.org/leap/15.4/#download

The last Debian that supports ppc32 was Debian 8:

https://www.debian.org/ports/powerpc/#powerpc

"Debian on 32-bit PowerPC (powerpc)
It first became an official release architecture with Debian GNU/Linux 2.2
(potato) and had retained that status until the publication of Debian 9 (stretch).
The last supported release for 32-bit PowerPC is Debian 8 (jessie)"

And Void Linux doesn't seem to support any PowerPC flavor:

https://voidlinux.org/download/

Adélie Linux supports ppc32. I can also add that FreeBSD also supports ppc32.

Checking about/build-platforms.rst I can see that we would only somewhat
care for FreeBSD here, since Debian 8 is already out of our support
window.

All that said, I don't have strong feelings against re-enabling it, specially
because this build issue was deliberated caused by us.

However, after re-enabling it, I would only care about build bugs that are
reproduced on ppc32 FreeBSD.



Daniel

> 
> 
> r~
> 
> 
> Richard Henderson (2):
>    common-user/host/ppc: Implement safe-syscall.inc.S
>    linux-user: Implment host/ppc/host-signal.h
> 
>   linux-user/include/host/ppc/host-signal.h |  39 ++++++++
>   common-user/host/ppc/safe-syscall.inc.S   | 107 ++++++++++++++++++++++
>   2 files changed, 146 insertions(+)
>   create mode 100644 linux-user/include/host/ppc/host-signal.h
>   create mode 100644 common-user/host/ppc/safe-syscall.inc.S
> 

Re: [PATCH for-7.1? 0/2] Re-enable ppc32 as a linux-user host

[Richard Henderson]

On 7/29/22 13:44, Daniel Henrique Barboza wrote:
> The last Debian that supports ppc32 was Debian 8:
> 
> https://www.debian.org/ports/powerpc/#powerpc
> 
> "Debian on 32-bit PowerPC (powerpc)
> It first became an official release architecture with Debian GNU/Linux 2.2
> (potato) and had retained that status until the publication of Debian 9 (stretch).
> The last supported release for 32-bit PowerPC is Debian 8 (jessie)"

It has been moved out of general support but remains in ports[1].

I was able to install a debian sid chroot with this today[2].
which should be good enough to continue compile-testing.
And Mark has hardware for actual testing.  Given that almost
all of the code overlaps with ppc64, I'm ok keeping it now.


r~


[1] http://ftp.de.debian.org/debian-ports/pool-powerpc/
[2] https://github.com/vivier/linux-user-test-scrips.git

Re: [PATCH 1/2] common-user/host/ppc: Implement safe-syscall.inc.S

[Daniel Henrique Barboza]

On 7/29/22 14:21, Richard Henderson wrote:
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---

Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>

>   common-user/host/ppc/safe-syscall.inc.S | 107 ++++++++++++++++++++++++
>   1 file changed, 107 insertions(+)
>   create mode 100644 common-user/host/ppc/safe-syscall.inc.S
> 
> diff --git a/common-user/host/ppc/safe-syscall.inc.S b/common-user/host/ppc/safe-syscall.inc.S
> new file mode 100644
> index 0000000000..0851f6c0b8
> --- /dev/null
> +++ b/common-user/host/ppc/safe-syscall.inc.S
> @@ -0,0 +1,107 @@
> +/*
> + * safe-syscall.inc.S : host-specific assembly fragment
> + * to handle signals occurring at the same time as system calls.
> + * This is intended to be included by common-user/safe-syscall.S
> + *
> + * Copyright (C) 2022 Linaro, Ltd.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +/*
> + * Standardize on the _CALL_FOO symbols used by GCC:
> + * Apple XCode does not define _CALL_DARWIN.
> + * Clang defines _CALL_ELF (64-bit) but not _CALL_SYSV (32-bit).
> + */
> +#if !defined(_CALL_SYSV) && \
> +    !defined(_CALL_DARWIN) && \
> +    !defined(_CALL_AIX) && \
> +    !defined(_CALL_ELF)
> +# if defined(__APPLE__)
> +#  define _CALL_DARWIN
> +# elif defined(__ELF__) && TCG_TARGET_REG_BITS == 32
> +#  define _CALL_SYSV
> +# else
> +#  error "Unknown ABI"
> +# endif
> +#endif
> +
> +#ifndef _CALL_SYSV
> +# error "Unsupported ABI"
> +#endif
> +
> +
> +        .global safe_syscall_base
> +        .global safe_syscall_start
> +        .global safe_syscall_end
> +        .type   safe_syscall_base, @function
> +
> +        .text
> +
> +        /*
> +         * This is the entry point for making a system call. The calling
> +         * convention here is that of a C varargs function with the
> +         * first argument an 'int *' to the signal_pending flag, the
> +         * second one the system call number (as a 'long'), and all further
> +         * arguments being syscall arguments (also 'long').
> +         */
> +safe_syscall_base:
> +        .cfi_startproc
> +        stwu    1, -8(1)
> +        .cfi_def_cfa_offset 8
> +        stw     30, 4(1)
> +        .cfi_offset 30, -4
> +
> +        /*
> +         * We enter with r3 == &signal_pending
> +         *               r4 == syscall number
> +         *               r5 ... r10 == syscall arguments
> +         *               and return the result in r3
> +         * and the syscall instruction needs
> +         *               r0 == syscall number
> +         *               r3 ... r8 == syscall arguments
> +         *               and returns the result in r3
> +         * Shuffle everything around appropriately.
> +         */
> +        mr      30, 3           /* signal_pending */
> +        mr      0, 4            /* syscall number */
> +        mr      3, 5            /* syscall arguments */
> +        mr      4, 6
> +        mr      5, 7
> +        mr      6, 8
> +        mr      7, 9
> +        mr      8, 10
> +
> +        /*
> +         * This next sequence of code works in conjunction with the
> +         * rewind_if_safe_syscall_function(). If a signal is taken
> +         * and the interrupted PC is anywhere between 'safe_syscall_start'
> +         * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'.
> +         * The code sequence must therefore be able to cope with this, and
> +         * the syscall instruction must be the final one in the sequence.
> +         */
> +safe_syscall_start:
> +        /* if signal_pending is non-zero, don't do the call */
> +        lwz     12, 0(30)
> +        cmpwi   0, 12, 0
> +        bne-    2f
> +        sc
> +safe_syscall_end:
> +        /* code path when we did execute the syscall */
> +        lwz     30, 4(1)        /* restore r30 */
> +        addi    1, 1, 8         /* restore stack */
> +        .cfi_restore 30
> +        .cfi_def_cfa_offset 0
> +        bnslr+                  /* return on success */
> +        b       safe_syscall_set_errno_tail
> +
> +        /* code path when we didn't execute the syscall */
> +2:      lwz     30, 4(1)
> +        addi    1, 1, 8
> +        addi    3, 0, QEMU_ERESTARTSYS
> +        b       safe_syscall_set_errno_tail
> +
> +        .cfi_endproc
> +
> +        .size   safe_syscall_base, .-safe_syscall_base

Re: [PATCH 2/2] linux-user: Implment host/ppc/host-signal.h

[Daniel Henrique Barboza]

commit title typo: "Implment"

On 7/29/22 14:21, Richard Henderson wrote:
> This commit re-enables ppc32 as a linux-user host,
> as existance of the directory is noted by configure.

s/existance/existence

> 
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1097
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---

Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>


>   linux-user/include/host/ppc/host-signal.h | 39 +++++++++++++++++++++++
>   1 file changed, 39 insertions(+)
>   create mode 100644 linux-user/include/host/ppc/host-signal.h
> 
> diff --git a/linux-user/include/host/ppc/host-signal.h b/linux-user/include/host/ppc/host-signal.h
> new file mode 100644
> index 0000000000..de25c803f5
> --- /dev/null
> +++ b/linux-user/include/host/ppc/host-signal.h
> @@ -0,0 +1,39 @@
> +/*
> + * host-signal.h: signal info dependent on the host architecture
> + *
> + * Copyright (c) 2022 Linaro Ltd.
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef PPC_HOST_SIGNAL_H
> +#define PPC_HOST_SIGNAL_H
> +
> +#include <asm/ptrace.h>
> +
> +/* The third argument to a SA_SIGINFO handler is ucontext_t. */
> +typedef ucontext_t host_sigcontext;
> +
> +static inline uintptr_t host_signal_pc(host_sigcontext *uc)
> +{
> +    return uc->uc_mcontext.regs->nip;
> +}
> +
> +static inline void host_signal_set_pc(host_sigcontext *uc, uintptr_t pc)
> +{
> +    uc->uc_mcontext.regs->nip = pc;
> +}
> +
> +static inline void *host_signal_mask(host_sigcontext *uc)
> +{
> +    return &uc->uc_sigmask;
> +}
> +
> +static inline bool host_signal_write(siginfo_t *info, host_sigcontext *uc)
> +{
> +    return uc->uc_mcontext.regs->trap != 0x400
> +        && (uc->uc_mcontext.regs->dsisr & 0x02000000);
> +}
> +
> +#endif

Re: [PATCH for-7.1? 0/2] Re-enable ppc32 as a linux-user host

[Lucas Mateus Martins Araujo e Castro]

[-- Attachment #1: Type: text/plain, Size: 2622 bytes --]


On 29/07/2022 17:44, Daniel Henrique Barboza wrote:
>
> On 7/29/22 14:21, Richard Henderson wrote:
>> This is, technically, a regression from 6.2, so it's not
>> implausible to apply before rc1.  Thoughts?
>
>
> In gitlab #1097 the author comments that:
>
> https://gitlab.com/qemu-project/qemu/-/issues/1097#note_1044810483
>
> "there are several distributions still available on 32-bit powerpc, e.g.
> Adélie Linux, for now still Void Linux, afaik Debian and OpenSUSE also
> still build packages"
>
> I checked these claims. Latest version OpenSuse LEAP doesn't support
> ppc32 bits:
>
> https://get.opensuse.org/leap/15.4/#download
>
> The last Debian that supports ppc32 was Debian 8:
>
> https://www.debian.org/ports/powerpc/#powerpc
>
> "Debian on 32-bit PowerPC (powerpc)
> It first became an official release architecture with Debian GNU/Linux 
> 2.2
> (potato) and had retained that status until the publication of Debian 
> 9 (stretch).
> The last supported release for 32-bit PowerPC is Debian 8 (jessie)"
>
> And Void Linux doesn't seem to support any PowerPC flavor:
>
> https://voidlinux.org/download/

The author is probably talking about Void Linux ppc as it seems it still 
support ppc

https://voidlinux-ppc.org/

>
> Adélie Linux supports ppc32. I can also add that FreeBSD also supports 
> ppc32.
>
> Checking about/build-platforms.rst I can see that we would only somewhat
> care for FreeBSD here, since Debian 8 is already out of our support
> window.
>
> All that said, I don't have strong feelings against re-enabling it, 
> specially
> because this build issue was deliberated caused by us.
>
> However, after re-enabling it, I would only care about build bugs that 
> are
> reproduced on ppc32 FreeBSD.
>
>
>
> Daniel
>
>>
>>
>> r~
>>
>>
>> Richard Henderson (2):
>>    common-user/host/ppc: Implement safe-syscall.inc.S
>>    linux-user: Implment host/ppc/host-signal.h
>>
>>   linux-user/include/host/ppc/host-signal.h |  39 ++++++++
>>   common-user/host/ppc/safe-syscall.inc.S   | 107 ++++++++++++++++++++++
>>   2 files changed, 146 insertions(+)
>>   create mode 100644 linux-user/include/host/ppc/host-signal.h
>>   create mode 100644 common-user/host/ppc/safe-syscall.inc.S
>>
>
-- 
Lucas Mateus M. Araujo e Castro
Instituto de Pesquisas ELDORADO 
<https://www.eldorado.org.br/?utm_campaign=assinatura_de_e-mail&utm_medium=email&utm_source=RD+Station>
Departamento Computação Embarcada
Analista de Software Trainee
Aviso Legal - Disclaimer <https://www.eldorado.org.br/disclaimer.html>

[-- Attachment #2: Type: text/html, Size: 4690 bytes --]

Re: [PATCH for-7.1? 0/2] Re-enable ppc32 as a linux-user host

[Richard Henderson]

On 7/29/22 18:21, Richard Henderson wrote:
> This is, technically, a regression from 6.2, so it's not
> implausible to apply before rc1.  Thoughts?
> 
> 
> r~
> 
> 
> Richard Henderson (2):
>    common-user/host/ppc: Implement safe-syscall.inc.S
>    linux-user: Implment host/ppc/host-signal.h

Queued to linux-user-next.


r~