Date: Fri, 31 Mar 2023 13:55:10 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: a54370f4abb6 - main - arm64: Ensure that thread0's PCB flags are initialized Message-ID: <202303311355.32VDtAFq083100@gitrepo.freebsd.org>
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The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=a54370f4abb6bc4e3ef25da97adb3262bacb5a4b commit a54370f4abb6bc4e3ef25da97adb3262bacb5a4b Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2023-03-31 13:50:34 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2023-03-31 13:50:34 +0000 arm64: Ensure that thread0's PCB flags are initialized On arm64, the PCB is stored at the top of the thread stack. For thread0 this comes from the static "initstack" region, which is placed in the .init_pagetable section, which is not part of the BSS and thus doesn't get zeroed by locore. (See the comment in ldscript.arm64.) It is thus possible for the pcb_flags field to be uninitialized, which can result in PCB_SINGLE_STEP being set. Fix this by simply initializing the field. A separate commit will move initstack out of the .init_pagetable section, since it has no reason to be there, but it is preferable to explicitly initialize PCB fields anyway. In particular, regular kernel stacks are not zeroed upon allocation, so we should be consistent here. Reviewed by: andrew MFC after: 1 week Sponsored by: Klara, Inc. Sponsored by: Juniper Networks Differential Revision: https://reviews.freebsd.org/D39343 --- sys/arm64/arm64/machdep.c | 1 + 1 file changed, 1 insertion(+) diff --git a/sys/arm64/arm64/machdep.c b/sys/arm64/arm64/machdep.c index b87c635048de..d9ea06952c54 100644 --- a/sys/arm64/arm64/machdep.c +++ b/sys/arm64/arm64/machdep.c @@ -380,6 +380,7 @@ init_proc0(vm_offset_t kstack) #endif thread0.td_pcb = (struct pcb *)(thread0.td_kstack + thread0.td_kstack_pages * PAGE_SIZE) - 1; + thread0.td_pcb->pcb_flags = 0; thread0.td_pcb->pcb_fpflags = 0; thread0.td_pcb->pcb_fpusaved = &thread0.td_pcb->pcb_fpustate; thread0.td_pcb->pcb_vfpcpu = UINT_MAX;
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