From: Florian Weimer <fweimer@redhat.com> To: Dave Hansen <dave.hansen@intel.com>, linux-mm <linux-mm@kvack.org>, x86@kernel.org, linux-arch <linux-arch@vger.kernel.org>, linux-x86_64@vger.kernel.org, Linux API <linux-api@vger.kernel.org> Subject: Re: pkeys: Support setting access rights for signal handlers Date: Sun, 10 Dec 2017 07:42:21 +0100 [thread overview] Message-ID: <5965d682-61b2-d7da-c4d7-c223aa396fab@redhat.com> (raw) In-Reply-To: <c034f693-95d1-65b8-2031-b969c2771fed@intel.com> On 12/10/2017 01:17 AM, Dave Hansen wrote: > On 12/09/2017 01:16 PM, Florian Weimer wrote: >> The attached patch addresses a problem with the current x86 pkey >> implementation, which makes default-readable pkeys unusable from signal >> handlers because the default init_pkru value blocks access. > > Thanks for looking into this! > > What do you mean by "default-readable pkeys"? > > I think you mean that, for any data that needs to be accessed to enter a > signal handler, it must be set to pkey=0 with the current > implementation. All other keys are inaccessible when entering a signal > handler because the "init" value disables access. Right, and for keys which are readable (but not writable) most of the time, so that date is readable, this breaks things. > My only nit with this is whether it is the *right* interface. The > signal vs. XSAVE state thing is pretty x86 specific and I doubt that > this will be the last feature that we encounter that needs special > signal behavior. The interface is not specific to XSAVE. To generic code, only the two signal mask manipulation functions are exposed. And I expect that we're going to need that for other (non-x86) implementations because they will have the same issue because the signal handler behavior will be identical. Thanks, Florian
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From: Florian Weimer <fweimer@redhat.com> To: Dave Hansen <dave.hansen@intel.com>, linux-mm <linux-mm@kvack.org>, x86@kernel.org, linux-arch <linux-arch@vger.kernel.org>, linux-x86_64@vger.kernel.org, Linux API <linux-api@vger.kernel.org> Subject: Re: pkeys: Support setting access rights for signal handlers Date: Sun, 10 Dec 2017 07:42:21 +0100 [thread overview] Message-ID: <5965d682-61b2-d7da-c4d7-c223aa396fab@redhat.com> (raw) In-Reply-To: <c034f693-95d1-65b8-2031-b969c2771fed@intel.com> On 12/10/2017 01:17 AM, Dave Hansen wrote: > On 12/09/2017 01:16 PM, Florian Weimer wrote: >> The attached patch addresses a problem with the current x86 pkey >> implementation, which makes default-readable pkeys unusable from signal >> handlers because the default init_pkru value blocks access. > > Thanks for looking into this! > > What do you mean by "default-readable pkeys"? > > I think you mean that, for any data that needs to be accessed to enter a > signal handler, it must be set to pkey=0 with the current > implementation. All other keys are inaccessible when entering a signal > handler because the "init" value disables access. Right, and for keys which are readable (but not writable) most of the time, so that date is readable, this breaks things. > My only nit with this is whether it is the *right* interface. The > signal vs. XSAVE state thing is pretty x86 specific and I doubt that > this will be the last feature that we encounter that needs special > signal behavior. The interface is not specific to XSAVE. To generic code, only the two signal mask manipulation functions are exposed. And I expect that we're going to need that for other (non-x86) implementations because they will have the same issue because the signal handler behavior will be identical. Thanks, Florian -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-12-10 6:42 UTC|newest] Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-12-09 21:16 pkeys: Support setting access rights for signal handlers Florian Weimer [not found] ` <5fee976a-42d4-d469-7058-b78ad8897219-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 2017-12-10 0:17 ` Dave Hansen 2017-12-10 0:17 ` Dave Hansen 2017-12-10 0:17 ` Dave Hansen 2017-12-10 6:42 ` Florian Weimer [this message] 2017-12-10 6:42 ` Florian Weimer 2017-12-11 16:13 ` Dave Hansen 2017-12-11 16:13 ` Dave Hansen 2017-12-12 23:13 ` Ram Pai 2017-12-12 23:13 ` Ram Pai 2017-12-13 2:14 ` Florian Weimer 2017-12-13 2:14 ` Florian Weimer 2017-12-13 11:35 ` Ram Pai 2017-12-13 11:35 ` Ram Pai [not found] ` <20171213113544.GG5460-LOE2q6NSToAxGrZ80giIafUQ3DHhIser@public.gmane.org> 2017-12-13 15:08 ` Florian Weimer 2017-12-13 15:08 ` Florian Weimer 2017-12-13 15:08 ` Florian Weimer 2017-12-13 15:22 ` Dave Hansen 2017-12-13 15:22 ` Dave Hansen 2017-12-13 15:40 ` Florian Weimer 2017-12-13 15:40 ` Florian Weimer 2017-12-14 0:17 ` Ram Pai 2017-12-14 0:17 ` Ram Pai 2017-12-14 11:21 ` Florian Weimer 2017-12-16 15:09 ` Ram Pai 2017-12-16 15:09 ` Ram Pai 2017-12-16 15:25 ` Florian Weimer 2017-12-16 15:25 ` Florian Weimer [not found] ` <2eba29f4-804d-b211-1293-52a567739cad-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 2017-12-16 17:20 ` Ram Pai 2017-12-16 17:20 ` Ram Pai 2017-12-16 17:20 ` Ram Pai 2017-12-18 11:00 ` Florian Weimer 2017-12-18 11:00 ` Florian Weimer
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