[PATCH v2] um: Allow building and running on older hosts

[PATCH v2] um: Allow building and running on older hosts

[Florian Fainelli]

Commit a78ff1112263 ("um: add extended processor state save/restore
support") and b6024b21fec8 ("um: extend fpstate to _xstate to support
YMM registers") forced the use of the x86 FP _xstate and
PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to
build UML nor run it anymore with these two commits applied because we
don't have definitions for struct _xstate nor these two ptrace requests.

We can determine at build time which fp context structure to check
against, just like we can keep using the old i387 fp save/restore if
PTRACE_GETRESET/SETREGSET are not defined.

Fixes: a78ff1112263 ("um: add extended processor state save/restore support")
Fixes: b6024b21fec8 ("um: extend fpstate to _xstate to support YMM registers")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
Changes in v2:

- re-arrange the #ifdef/curly braces to not take the branch

 arch/x86/um/os-Linux/registers.c | 12 ++++++++----
 arch/x86/um/user-offsets.c       |  4 ++++
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/x86/um/os-Linux/registers.c b/arch/x86/um/os-Linux/registers.c
index 00f54a91bb4b..28775f55bde2 100644
--- a/arch/x86/um/os-Linux/registers.c
+++ b/arch/x86/um/os-Linux/registers.c
@@ -26,6 +26,7 @@ int save_i387_registers(int pid, unsigned long *fp_regs)
 
 int save_fp_registers(int pid, unsigned long *fp_regs)
 {
+#ifdef PTRACE_GETREGSET
 	struct iovec iov;
 
 	if (have_xstate_support) {
@@ -34,9 +35,9 @@ int save_fp_registers(int pid, unsigned long *fp_regs)
 		if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
 			return -errno;
 		return 0;
-	} else {
+	} else
+#endif
 		return save_i387_registers(pid, fp_regs);
-	}
 }
 
 int restore_i387_registers(int pid, unsigned long *fp_regs)
@@ -48,6 +49,7 @@ int restore_i387_registers(int pid, unsigned long *fp_regs)
 
 int restore_fp_registers(int pid, unsigned long *fp_regs)
 {
+#ifdef PTRACE_SETREGSET
 	struct iovec iov;
 
 	if (have_xstate_support) {
@@ -56,9 +58,9 @@ int restore_fp_registers(int pid, unsigned long *fp_regs)
 		if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
 			return -errno;
 		return 0;
-	} else {
+	} else
+#endif
 		return restore_i387_registers(pid, fp_regs);
-	}
 }
 
 #ifdef __i386__
@@ -122,6 +124,7 @@ int put_fp_registers(int pid, unsigned long *regs)
 
 void arch_init_registers(int pid)
 {
+#ifdef PTRACE_GETREGSET
 	struct _xstate fp_regs;
 	struct iovec iov;
 
@@ -129,6 +132,7 @@ void arch_init_registers(int pid)
 	iov.iov_len = sizeof(struct _xstate);
 	if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) == 0)
 		have_xstate_support = 1;
+#endif
 }
 #endif
 
diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
index cb3c22370cf5..8af0fb5d2780 100644
--- a/arch/x86/um/user-offsets.c
+++ b/arch/x86/um/user-offsets.c
@@ -50,7 +50,11 @@ void foo(void)
 	DEFINE(HOST_GS, GS);
 	DEFINE(HOST_ORIG_AX, ORIG_EAX);
 #else
+#if defined(PTRACE_GETREGSET) && defined(PTRACE_SETREGSET)
 	DEFINE(HOST_FP_SIZE, sizeof(struct _xstate) / sizeof(unsigned long));
+#else
+	DEFINE(HOST_FP_SIZE, sizeof(struct _fpstate) / sizeof(unsigned long));
+#endif
 	DEFINE_LONGS(HOST_BX, RBX);
 	DEFINE_LONGS(HOST_CX, RCX);
 	DEFINE_LONGS(HOST_DI, RDI);
-- 
2.12.2

Re: [PATCH v2] um: Allow building and running on older hosts

[Thomas Meyer]

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> Am 25.05.2017 um 20:36 schrieb Florian Fainelli <f.fainelli@gmail.com>:
> 
> Commit a78ff1112263 ("um: add extended processor state save/restore
> support") and b6024b21fec8 ("um: extend fpstate to _xstate to support
> YMM registers") forced the use of the x86 FP _xstate and
> PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to
> build UML nor run it anymore with these two commits applied because we
> don't have definitions for struct _xstate nor these two ptrace requests.

Btw. what soy you mean with older host? I need to revert two commits to make an UML kernel work again on a Fedora 25 installation.

> 
> We can determine at build time which fp context structure to check
> against, just like we can keep using the old i387 fp save/restore if
> PTRACE_GETRESET/SETREGSET are not defined.
> 
> Fixes: a78ff1112263 ("um: add extended processor state save/restore support")
> Fixes: b6024b21fec8 ("um: extend fpstate to _xstate to support YMM registers")
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
> Changes in v2:
> 
> - re-arrange the #ifdef/curly braces to not take the branch
> 
> arch/x86/um/os-Linux/registers.c | 12 ++++++++----
> arch/x86/um/user-offsets.c       |  4 ++++
> 2 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/um/os-Linux/registers.c b/arch/x86/um/os-Linux/registers.c
> index 00f54a91bb4b..28775f55bde2 100644
> --- a/arch/x86/um/os-Linux/registers.c
> +++ b/arch/x86/um/os-Linux/registers.c
> @@ -26,6 +26,7 @@ int save_i387_registers(int pid, unsigned long *fp_regs)
> 
> int save_fp_registers(int pid, unsigned long *fp_regs)
> {
> +#ifdef PTRACE_GETREGSET
>    struct iovec iov;
> 
>    if (have_xstate_support) {
> @@ -34,9 +35,9 @@ int save_fp_registers(int pid, unsigned long *fp_regs)
>        if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
>            return -errno;
>        return 0;
> -    } else {
> +    } else
> +#endif
>        return save_i387_registers(pid, fp_regs);
> -    }
> }
> 
> int restore_i387_registers(int pid, unsigned long *fp_regs)
> @@ -48,6 +49,7 @@ int restore_i387_registers(int pid, unsigned long *fp_regs)
> 
> int restore_fp_registers(int pid, unsigned long *fp_regs)
> {
> +#ifdef PTRACE_SETREGSET
>    struct iovec iov;
> 
>    if (have_xstate_support) {
> @@ -56,9 +58,9 @@ int restore_fp_registers(int pid, unsigned long *fp_regs)
>        if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
>            return -errno;
>        return 0;
> -    } else {
> +    } else
> +#endif
>        return restore_i387_registers(pid, fp_regs);
> -    }
> }
> 
> #ifdef __i386__
> @@ -122,6 +124,7 @@ int put_fp_registers(int pid, unsigned long *regs)
> 
> void arch_init_registers(int pid)
> {
> +#ifdef PTRACE_GETREGSET
>    struct _xstate fp_regs;
>    struct iovec iov;
> 
> @@ -129,6 +132,7 @@ void arch_init_registers(int pid)
>    iov.iov_len = sizeof(struct _xstate);
>    if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) == 0)
>        have_xstate_support = 1;

In my setup above call works correctly and so have_xstate_support will be set, but save_fp_registers fails with errno 4 or so...

> +#endif
> }
> #endif
> 
> diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
> index cb3c22370cf5..8af0fb5d2780 100644
> --- a/arch/x86/um/user-offsets.c
> +++ b/arch/x86/um/user-offsets.c
> @@ -50,7 +50,11 @@ void foo(void)
>    DEFINE(HOST_GS, GS);
>    DEFINE(HOST_ORIG_AX, ORIG_EAX);
> #else
> +#if defined(PTRACE_GETREGSET) && defined(PTRACE_SETREGSET)
>    DEFINE(HOST_FP_SIZE, sizeof(struct _xstate) / sizeof(unsigned long));
> +#else
> +    DEFINE(HOST_FP_SIZE, sizeof(struct _fpstate) / sizeof(unsigned long));
> +#endif
>    DEFINE_LONGS(HOST_BX, RBX);
>    DEFINE_LONGS(HOST_CX, RCX);
>    DEFINE_LONGS(HOST_DI, RDI);
> -- 
> 2.12.2
> 

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Re: [PATCH v2] um: Allow building and running on older hosts

[Florian Fainelli]

On 05/25/2017 12:51 PM, Thomas Meyer wrote:
> 
>> Am 25.05.2017 um 20:36 schrieb Florian Fainelli <f.fainelli@gmail.com>:
>>
>> Commit a78ff1112263 ("um: add extended processor state save/restore
>> support") and b6024b21fec8 ("um: extend fpstate to _xstate to support
>> YMM registers") forced the use of the x86 FP _xstate and
>> PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to
>> build UML nor run it anymore with these two commits applied because we
>> don't have definitions for struct _xstate nor these two ptrace requests.
> 
> Btw. what soy you mean with older host? I need to revert two commits to make an UML kernel work again on a Fedora 25 installation.

This is centos 6.9, so kernel 2.6.32 and glibc 2.12, this neither has
xstate nor PTRACE_GETREGSET/SETREGSET, hence this patch.

> 
>>
>> We can determine at build time which fp context structure to check
>> against, just like we can keep using the old i387 fp save/restore if
>> PTRACE_GETRESET/SETREGSET are not defined.
>>
>> Fixes: a78ff1112263 ("um: add extended processor state save/restore support")
>> Fixes: b6024b21fec8 ("um: extend fpstate to _xstate to support YMM registers")
>> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
>> ---
>> Changes in v2:
>>
>> - re-arrange the #ifdef/curly braces to not take the branch
>>
>> arch/x86/um/os-Linux/registers.c | 12 ++++++++----
>> arch/x86/um/user-offsets.c       |  4 ++++
>> 2 files changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/um/os-Linux/registers.c b/arch/x86/um/os-Linux/registers.c
>> index 00f54a91bb4b..28775f55bde2 100644
>> --- a/arch/x86/um/os-Linux/registers.c
>> +++ b/arch/x86/um/os-Linux/registers.c
>> @@ -26,6 +26,7 @@ int save_i387_registers(int pid, unsigned long *fp_regs)
>>
>> int save_fp_registers(int pid, unsigned long *fp_regs)
>> {
>> +#ifdef PTRACE_GETREGSET
>>    struct iovec iov;
>>
>>    if (have_xstate_support) {
>> @@ -34,9 +35,9 @@ int save_fp_registers(int pid, unsigned long *fp_regs)
>>        if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
>>            return -errno;
>>        return 0;
>> -    } else {
>> +    } else
>> +#endif
>>        return save_i387_registers(pid, fp_regs);
>> -    }
>> }
>>
>> int restore_i387_registers(int pid, unsigned long *fp_regs)
>> @@ -48,6 +49,7 @@ int restore_i387_registers(int pid, unsigned long *fp_regs)
>>
>> int restore_fp_registers(int pid, unsigned long *fp_regs)
>> {
>> +#ifdef PTRACE_SETREGSET
>>    struct iovec iov;
>>
>>    if (have_xstate_support) {
>> @@ -56,9 +58,9 @@ int restore_fp_registers(int pid, unsigned long *fp_regs)
>>        if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
>>            return -errno;
>>        return 0;
>> -    } else {
>> +    } else
>> +#endif
>>        return restore_i387_registers(pid, fp_regs);
>> -    }
>> }
>>
>> #ifdef __i386__
>> @@ -122,6 +124,7 @@ int put_fp_registers(int pid, unsigned long *regs)
>>
>> void arch_init_registers(int pid)
>> {
>> +#ifdef PTRACE_GETREGSET
>>    struct _xstate fp_regs;
>>    struct iovec iov;
>>
>> @@ -129,6 +132,7 @@ void arch_init_registers(int pid)
>>    iov.iov_len = sizeof(struct _xstate);
>>    if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) == 0)
>>        have_xstate_support = 1;
> 
> In my setup above call works correctly and so have_xstate_support will be set, but save_fp_registers fails with errno 4 or so...
> 
>> +#endif
>> }
>> #endif
>>
>> diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
>> index cb3c22370cf5..8af0fb5d2780 100644
>> --- a/arch/x86/um/user-offsets.c
>> +++ b/arch/x86/um/user-offsets.c
>> @@ -50,7 +50,11 @@ void foo(void)
>>    DEFINE(HOST_GS, GS);
>>    DEFINE(HOST_ORIG_AX, ORIG_EAX);
>> #else
>> +#if defined(PTRACE_GETREGSET) && defined(PTRACE_SETREGSET)
>>    DEFINE(HOST_FP_SIZE, sizeof(struct _xstate) / sizeof(unsigned long));
>> +#else
>> +    DEFINE(HOST_FP_SIZE, sizeof(struct _fpstate) / sizeof(unsigned long));
>> +#endif
>>    DEFINE_LONGS(HOST_BX, RBX);
>>    DEFINE_LONGS(HOST_CX, RCX);
>>    DEFINE_LONGS(HOST_DI, RDI);
>> -- 
>> 2.12.2
>>


-- 
Florian

Re: [PATCH v2] um: Allow building and running on older hosts

[Richard Weinberger]

Thomas, Florian,

Am 26.05.2017 um 00:28 schrieb Florian Fainelli:
> On 05/25/2017 12:51 PM, Thomas Meyer wrote:
>>
>>> Am 25.05.2017 um 20:36 schrieb Florian Fainelli <f.fainelli@gmail.com>:
>>>
>>> Commit a78ff1112263 ("um: add extended processor state save/restore
>>> support") and b6024b21fec8 ("um: extend fpstate to _xstate to support
>>> YMM registers") forced the use of the x86 FP _xstate and
>>> PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to
>>> build UML nor run it anymore with these two commits applied because we
>>> don't have definitions for struct _xstate nor these two ptrace requests.
>>
>> Btw. what soy you mean with older host? I need to revert two commits to make an UML kernel work again on a Fedora 25 installation.
> 
> This is centos 6.9, so kernel 2.6.32 and glibc 2.12, this neither has
> xstate nor PTRACE_GETREGSET/SETREGSET, hence this patch.

Commits a78ff1112263 and b6024b21fec8 are broken.
You see two different issues.
Eli, please have a look too.

Thanks,
//richard

Re: [PATCH v2] um: Allow building and running on older hosts

[Florian Fainelli]

On 05/25/2017 03:34 PM, Richard Weinberger wrote:
> Thomas, Florian,
> 
> Am 26.05.2017 um 00:28 schrieb Florian Fainelli:
>> On 05/25/2017 12:51 PM, Thomas Meyer wrote:
>>>
>>>> Am 25.05.2017 um 20:36 schrieb Florian Fainelli <f.fainelli@gmail.com>:
>>>>
>>>> Commit a78ff1112263 ("um: add extended processor state save/restore
>>>> support") and b6024b21fec8 ("um: extend fpstate to _xstate to support
>>>> YMM registers") forced the use of the x86 FP _xstate and
>>>> PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to
>>>> build UML nor run it anymore with these two commits applied because we
>>>> don't have definitions for struct _xstate nor these two ptrace requests.
>>>
>>> Btw. what soy you mean with older host? I need to revert two commits to make an UML kernel work again on a Fedora 25 installation.
>>
>> This is centos 6.9, so kernel 2.6.32 and glibc 2.12, this neither has
>> xstate nor PTRACE_GETREGSET/SETREGSET, hence this patch.
> 
> Commits a78ff1112263 and b6024b21fec8 are broken.
> You see two different issues.
> Eli, please have a look too.

Eli, can we get an answer here? And Thomas what's that problem that
Richard is referring to?
-- 
Florian

Re: [PATCH v2] um: Allow building and running on older hosts

[Richard Weinberger]

Florian,

On Thu, May 25, 2017 at 8:36 PM, Florian Fainelli <f.fainelli@gmail.com> wrote:
> Commit a78ff1112263 ("um: add extended processor state save/restore
> support") and b6024b21fec8 ("um: extend fpstate to _xstate to support
> YMM registers") forced the use of the x86 FP _xstate and
> PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to
> build UML nor run it anymore with these two commits applied because we
> don't have definitions for struct _xstate nor these two ptrace requests.
>
> We can determine at build time which fp context structure to check
> against, just like we can keep using the old i387 fp save/restore if
> PTRACE_GETRESET/SETREGSET are not defined.
>
> Fixes: a78ff1112263 ("um: add extended processor state save/restore support")
> Fixes: b6024b21fec8 ("um: extend fpstate to _xstate to support YMM registers")
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

Both patches applied. Thanks a lot for fixing these regressions!

-- 
Thanks,
//richard