From: Borislav Petkov <bp@alien8.de>
To: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Andy Lutomirski <luto@kernel.org>,
Balbir Singh <bsingharora@gmail.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
"H . J . Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
Weijiang Yang <weijiang.yang@intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
John Allen <john.allen@amd.com>,
kcc@google.com, eranian@google.com, rppt@kernel.org,
jamorris@linux.microsoft.com, dethoma@microsoft.com,
akpm@linux-foundation.org, Andrew.Cooper3@citrix.com,
christina.schimpe@intel.com, david@redhat.com,
debug@rivosinc.com
Subject: Re: [PATCH v7 38/41] x86/fpu: Add helper for initing features
Date: Sat, 11 Mar 2023 13:54:42 +0100 [thread overview]
Message-ID: <ZAx6Egh6U5SCZEby@zn.tnic> (raw)
In-Reply-To: <20230227222957.24501-39-rick.p.edgecombe@intel.com>
On Mon, Feb 27, 2023 at 02:29:54PM -0800, Rick Edgecombe wrote:
> Subject: Re: [PATCH v7 38/41] x86/fpu: Add helper for initing features
"initializing"
> If an xfeature is saved in a buffer, the xfeature's bit will be set in
> xsave->header.xfeatures. The CPU may opt to not save the xfeature if it
> is in it's init state. In this case the xfeature buffer address cannot
"its"
> be retrieved with get_xsave_addr().
>
> Future patches will need to handle the case of writing to an xfeature
> that may not be saved. So provide helpers to init an xfeature in an
> xsave buffer.
>
> This could of course be done directly by reaching into the xsave buffer,
> however this would not be robust against future changes to optimize the
> xsave buffer by compacting it. In that case the xsave buffer would need
> to be re-arranged as well. So the logic properly belongs encapsulated
> in a helper where the logic can be unified.
>
> Tested-by: Pengfei Xu <pengfei.xu@intel.com>
> Tested-by: John Allen <john.allen@amd.com>
> Tested-by: Kees Cook <keescook@chromium.org>
> Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
>
> ---
> v2:
> - New patch
> ---
> arch/x86/kernel/fpu/xstate.c | 58 +++++++++++++++++++++++++++++-------
> arch/x86/kernel/fpu/xstate.h | 6 ++++
> 2 files changed, 53 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
> index 13a80521dd51..3ff80be0a441 100644
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -934,6 +934,24 @@ static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
> return (void *)xsave + xfeature_get_offset(xcomp_bv, xfeature_nr);
> }
>
> +static int xsave_buffer_access_checks(int xfeature_nr)
Function name needs a verb.
> +{
> + /*
> + * Do we even *have* xsave state?
> + */
That comment is superfluous.
> + if (!boot_cpu_has(X86_FEATURE_XSAVE))
check_for_deprecated_apis: WARNING: arch/x86/kernel/fpu/xstate.c:942: Do not use boot_cpu_has() - use cpu_feature_enabled() instead.
> + return 1;
> +
> + /*
> + * We should not ever be requesting features that we
Please use passive voice in your commit message: no "we" or "I", etc,
and describe your changes in imperative mood.
> + * have not enabled.
> + */
> + if (WARN_ON_ONCE(!xfeature_enabled(xfeature_nr)))
> + return 1;
> +
> + return 0;
> +}
> +
> /*
> * Given the xsave area and a state inside, this function returns the
> * address of the state.
> @@ -954,17 +972,7 @@ static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
> */
> void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
> {
> - /*
> - * Do we even *have* xsave state?
> - */
> - if (!boot_cpu_has(X86_FEATURE_XSAVE))
> - return NULL;
> -
> - /*
> - * We should not ever be requesting features that we
> - * have not enabled.
> - */
> - if (WARN_ON_ONCE(!xfeature_enabled(xfeature_nr)))
> + if (xsave_buffer_access_checks(xfeature_nr))
> return NULL;
>
> /*
> @@ -984,6 +992,34 @@ void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
> return __raw_xsave_addr(xsave, xfeature_nr);
> }
>
> +/*
> + * Given the xsave area and a state inside, this function
> + * initializes an xfeature in the buffer.
s/this function initializes/initialize/
> + *
> + * get_xsave_addr() will return NULL if the feature bit is
> + * not present in the header. This function will make it so
> + * the xfeature buffer address is ready to be retrieved by
> + * get_xsave_addr().
So users of get_xsave_addr() would have to know that they would need to
call init_xfeature()?
I think the better approach would be:
void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr, bool init)
and then that @init controls whether get_xsave_addr() should init the
buffer.
And then you don't have to have a bunch of small functions here and
there and know when to call what but get_xsave_addr() would simply DTRT.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2023-03-11 12:54 UTC|newest]
Thread overview: 159+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-27 22:29 [PATCH v7 00/41] Shadow stacks for userspace Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 01/41] Documentation/x86: Add CET shadow stack description Rick Edgecombe
2023-03-01 14:21 ` Szabolcs Nagy
2023-03-01 14:38 ` Szabolcs Nagy
2023-03-01 18:07 ` Edgecombe, Rick P
2023-03-01 18:32 ` Edgecombe, Rick P
2023-03-02 16:34 ` szabolcs.nagy
2023-03-03 22:35 ` Edgecombe, Rick P
2023-03-06 16:20 ` szabolcs.nagy
2023-03-06 16:31 ` Florian Weimer
2023-03-06 18:08 ` Edgecombe, Rick P
2023-03-07 13:03 ` szabolcs.nagy
2023-03-07 14:00 ` Florian Weimer
2023-03-07 16:14 ` Szabolcs Nagy
2023-03-06 18:05 ` Edgecombe, Rick P
2023-03-06 20:31 ` Liang, Kan
2023-03-02 16:14 ` szabolcs.nagy
2023-03-02 21:17 ` Edgecombe, Rick P
2023-03-03 16:30 ` szabolcs.nagy
2023-03-03 16:57 ` H.J. Lu
2023-03-03 17:39 ` szabolcs.nagy
2023-03-03 17:50 ` H.J. Lu
2023-03-03 17:41 ` Edgecombe, Rick P
2023-02-27 22:29 ` [PATCH v7 02/41] x86/shstk: Add Kconfig option for shadow stack Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 03/41] x86/cpufeatures: Add CPU feature flags for shadow stacks Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 04/41] x86/cpufeatures: Enable CET CR4 bit for shadow stack Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 05/41] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 06/41] x86/fpu: Add helper for modifying xstate Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 07/41] x86: Move control protection handler to separate file Rick Edgecombe
2023-03-01 15:38 ` Borislav Petkov
2023-02-27 22:29 ` [PATCH v7 08/41] x86/shstk: Add user control-protection fault handler Rick Edgecombe
2023-03-01 18:06 ` Borislav Petkov
2023-03-01 18:14 ` Edgecombe, Rick P
2023-03-01 18:37 ` Borislav Petkov
2023-02-27 22:29 ` [PATCH v7 09/41] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 10/41] x86/mm: Move pmd_write(), pud_write() up in the file Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 11/41] mm: Introduce pte_mkwrite_kernel() Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 12/41] s390/mm: Introduce pmd_mkwrite_kernel() Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 13/41] mm: Make pte_mkwrite() take a VMA Rick Edgecombe
2023-03-01 7:03 ` Christophe Leroy
2023-03-01 8:16 ` David Hildenbrand
2023-03-02 12:19 ` Borislav Petkov
2023-02-27 22:29 ` [PATCH v7 14/41] x86/mm: Introduce _PAGE_SAVED_DIRTY Rick Edgecombe
2023-03-02 12:48 ` Borislav Petkov
2023-03-02 17:01 ` Edgecombe, Rick P
2023-02-27 22:29 ` [PATCH v7 15/41] x86/mm: Update ptep/pmdp_set_wrprotect() for _PAGE_SAVED_DIRTY Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 16/41] x86/mm: Start actually marking _PAGE_SAVED_DIRTY Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 17/41] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 18/41] mm: Introduce VM_SHADOW_STACK for shadow stack memory Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 19/41] x86/mm: Check shadow stack page fault errors Rick Edgecombe
2023-03-03 14:00 ` Borislav Petkov
2023-03-03 14:39 ` Dave Hansen
2023-02-27 22:29 ` [PATCH v7 20/41] x86/mm: Teach pte_mkwrite() about stack memory Rick Edgecombe
2023-03-03 15:37 ` Borislav Petkov
2023-02-27 22:29 ` [PATCH v7 21/41] mm: Add guard pages around a shadow stack Rick Edgecombe
2023-03-06 8:08 ` Borislav Petkov
2023-03-07 1:29 ` Edgecombe, Rick P
2023-03-07 10:32 ` Borislav Petkov
2023-03-07 10:44 ` David Hildenbrand
2023-03-08 22:48 ` Edgecombe, Rick P
2023-03-17 17:09 ` Deepak Gupta
2023-02-27 22:29 ` [PATCH v7 22/41] mm/mmap: Add shadow stack pages to memory accounting Rick Edgecombe
2023-03-06 13:01 ` Borislav Petkov
2023-03-06 18:11 ` Edgecombe, Rick P
2023-03-06 18:16 ` Borislav Petkov
2023-03-07 10:42 ` David Hildenbrand
2023-03-17 17:12 ` Deepak Gupta
2023-03-17 17:16 ` Dave Hansen
2023-03-17 17:28 ` Deepak Gupta
2023-03-17 17:42 ` Edgecombe, Rick P
2023-03-17 19:26 ` Deepak Gupta
2023-02-27 22:29 ` [PATCH v7 23/41] mm: Re-introduce vm_flags to do_mmap() Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 24/41] mm: Don't allow write GUPs to shadow stack memory Rick Edgecombe
2023-03-06 13:10 ` Borislav Petkov
2023-03-06 18:15 ` Andy Lutomirski
2023-03-06 18:33 ` Edgecombe, Rick P
2023-03-06 18:57 ` Andy Lutomirski
2023-03-07 1:47 ` Edgecombe, Rick P
2023-03-17 17:05 ` Deepak Gupta
2023-02-27 22:29 ` [PATCH v7 25/41] x86/mm: Introduce MAP_ABOVE4G Rick Edgecombe
2023-03-06 18:09 ` Borislav Petkov
2023-03-07 1:10 ` Edgecombe, Rick P
2023-02-27 22:29 ` [PATCH v7 26/41] mm: Warn on shadow stack memory in wrong vma Rick Edgecombe
2023-03-08 8:53 ` Borislav Petkov
2023-03-08 23:36 ` Edgecombe, Rick P
2023-02-27 22:29 ` [PATCH v7 27/41] x86/mm: Warn if create Write=0,Dirty=1 with raw prot Rick Edgecombe
2023-02-27 22:54 ` Kees Cook
2023-03-08 9:23 ` Borislav Petkov
2023-03-08 23:35 ` Edgecombe, Rick P
2023-02-27 22:29 ` [PATCH v7 28/41] x86: Introduce userspace API for shadow stack Rick Edgecombe
2023-03-08 10:27 ` Borislav Petkov
2023-03-08 23:32 ` Edgecombe, Rick P
2023-03-09 12:57 ` Borislav Petkov
2023-03-09 16:56 ` Edgecombe, Rick P
2023-03-09 23:51 ` Borislav Petkov
2023-03-10 1:13 ` Edgecombe, Rick P
2023-03-10 2:03 ` H.J. Lu
2023-03-10 20:00 ` H.J. Lu
2023-03-10 20:27 ` Edgecombe, Rick P
2023-03-10 20:43 ` H.J. Lu
2023-03-10 21:01 ` Edgecombe, Rick P
2023-03-10 11:40 ` Borislav Petkov
2023-02-27 22:29 ` [PATCH v7 29/41] x86/shstk: Add user-mode shadow stack support Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 30/41] x86/shstk: Handle thread shadow stack Rick Edgecombe
2023-03-02 17:34 ` Szabolcs Nagy
2023-03-02 21:48 ` Edgecombe, Rick P
2023-03-08 15:26 ` Borislav Petkov
2023-03-08 20:03 ` Edgecombe, Rick P
2023-03-09 14:12 ` Borislav Petkov
2023-03-09 16:59 ` Edgecombe, Rick P
2023-03-09 17:04 ` Borislav Petkov
2023-03-09 20:29 ` Edgecombe, Rick P
2023-02-27 22:29 ` [PATCH v7 31/41] x86/shstk: Introduce routines modifying shstk Rick Edgecombe
2023-03-09 16:48 ` Borislav Petkov
2023-03-09 17:03 ` Edgecombe, Rick P
2023-03-09 17:22 ` Borislav Petkov
2023-02-27 22:29 ` [PATCH v7 32/41] x86/shstk: Handle signals for shadow stack Rick Edgecombe
2023-03-09 17:02 ` Borislav Petkov
2023-03-09 17:16 ` Edgecombe, Rick P
2023-03-09 23:35 ` Borislav Petkov
2023-02-27 22:29 ` [PATCH v7 33/41] x86/shstk: Introduce map_shadow_stack syscall Rick Edgecombe
2023-03-02 17:22 ` Szabolcs Nagy
2023-03-02 21:21 ` Edgecombe, Rick P
2023-03-09 18:55 ` Deepak Gupta
2023-03-09 19:39 ` Edgecombe, Rick P
2023-03-09 21:08 ` Deepak Gupta
2023-03-10 0:14 ` Edgecombe, Rick P
2023-03-10 21:00 ` Deepak Gupta
2023-03-10 21:43 ` Edgecombe, Rick P
2023-03-16 20:07 ` Deepak Gupta
2023-03-14 7:19 ` Mike Rapoport
2023-03-16 19:30 ` Deepak Gupta
2023-03-20 11:35 ` Szabolcs Nagy
2023-03-10 16:11 ` Borislav Petkov
2023-03-10 17:12 ` Edgecombe, Rick P
2023-03-10 20:05 ` Borislav Petkov
2023-03-10 20:19 ` Edgecombe, Rick P
2023-03-10 20:26 ` Borislav Petkov
2023-02-27 22:29 ` [PATCH v7 34/41] x86/shstk: Support WRSS for userspace Rick Edgecombe
2023-03-10 16:44 ` Borislav Petkov
2023-03-10 17:16 ` Edgecombe, Rick P
2023-02-27 22:29 ` [PATCH v7 35/41] x86: Expose thread features in /proc/$PID/status Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 36/41] x86/shstk: Wire in shadow stack interface Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 37/41] selftests/x86: Add shadow stack test Rick Edgecombe
2023-02-27 22:29 ` [PATCH v7 38/41] x86/fpu: Add helper for initing features Rick Edgecombe
2023-03-11 12:54 ` Borislav Petkov [this message]
2023-03-13 2:45 ` Edgecombe, Rick P
2023-03-13 11:03 ` Borislav Petkov
2023-03-13 16:10 ` Edgecombe, Rick P
2023-03-13 17:10 ` Borislav Petkov
2023-03-13 23:31 ` Edgecombe, Rick P
2023-02-27 22:29 ` [PATCH v7 39/41] x86: Add PTRACE interface for shadow stack Rick Edgecombe
2023-03-11 15:06 ` Borislav Petkov
2023-03-13 2:53 ` Edgecombe, Rick P
2023-02-27 22:29 ` [PATCH v7 40/41] x86/shstk: Add ARCH_SHSTK_UNLOCK Rick Edgecombe
2023-03-11 15:11 ` Borislav Petkov
2023-03-13 3:04 ` Edgecombe, Rick P
2023-03-13 11:05 ` Borislav Petkov
2023-02-27 22:29 ` [PATCH v7 41/41] x86/shstk: Add ARCH_SHSTK_STATUS Rick Edgecombe
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