Date: Wed, 27 May 2026 15:24:13 +0000 From: Andrew Turner <andrew@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Cc: Harry Moulton <harry.moulton@arm.com> Subject: git: bb9497a2d462 - main - arm64: Add vm_page_t MTE flags Message-ID: <6a170c9d.26e27.6932ecae@gitrepo.freebsd.org>
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The branch main has been updated by andrew: URL: https://cgit.FreeBSD.org/src/commit/?id=bb9497a2d462e668455d0a561bd5677f447b4acf commit bb9497a2d462e668455d0a561bd5677f447b4acf Author: Harry Moulton <harry.moulton@arm.com> AuthorDate: 2026-05-18 09:09:23 +0000 Commit: Andrew Turner <andrew@FreeBSD.org> CommitDate: 2026-05-27 15:22:26 +0000 arm64: Add vm_page_t MTE flags To track which pages have MTE tags. Add a flag field to md_page. We can then use this in MD code to mark which pages have MTE tags. Reviewed by: andrew Sponsored by: Arm Ltd Differential Revision: https://reviews.freebsd.org/D55954 --- sys/arm64/arm64/mte.c | 38 ++++++++++++++++++++++++++++++++++++++ sys/arm64/arm64/pmap.c | 1 + sys/arm64/include/cpu.h | 2 ++ sys/arm64/include/pmap.h | 3 +++ 4 files changed, 44 insertions(+) diff --git a/sys/arm64/arm64/mte.c b/sys/arm64/arm64/mte.c index 88f394dc72c3..ba5d9df3b01c 100644 --- a/sys/arm64/arm64/mte.c +++ b/sys/arm64/arm64/mte.c @@ -49,6 +49,13 @@ static u_int __read_mostly mte_version = 0; struct thread *mte_switch(struct thread *); +/* Fetch the block size used by tag load and store instructions */ +static inline size_t +mte_block_size(void) +{ + return (sizeof(int) << GMID_BS_SIZE(READ_SPECIALREG(GMID_EL1_REG))); +} + static void mte_update_sctlr(struct thread *td, uint64_t sctlr) { @@ -57,6 +64,37 @@ mte_update_sctlr(struct thread *td, uint64_t sctlr) td->td_md.md_sctlr |= sctlr; } +/** + * Clear/sync the allocation tags for a given page. This should be done on + * allocation of a page to ensure a tag check fault does not occur immediately + * after accessing newly tagged memory. + */ +void +mte_sync_tags(vm_page_t page) +{ + char *addr; + size_t block_size; + + if (!MTE_HAS_TAG_CHECK) + return; + + /* don't clear the tags on a page that's already setup for mte */ + if ((page->md.pv_flags & PV_MTE_TAGGED) != 0) + return; + + block_size = mte_block_size(); + addr = PHYS_TO_DMAP(page->phys_addr); + + for (size_t count = 0; count < PAGE_SIZE; + count += block_size, addr += block_size) + asm volatile( + ".arch_extension memtag \n" + "stgm xzr, [%0] \n" + ".arch_extension nomemtag" : : "r" (addr)); + + page->md.pv_flags |= PV_MTE_TAGGED; +} + void mte_fork(struct thread *new_td, struct thread *orig_td) { diff --git a/sys/arm64/arm64/pmap.c b/sys/arm64/arm64/pmap.c index 0aa1ee8d5801..6914fc13b065 100644 --- a/sys/arm64/arm64/pmap.c +++ b/sys/arm64/arm64/pmap.c @@ -6922,6 +6922,7 @@ pmap_zero_page(vm_page_t m) void *va = VM_PAGE_TO_DMAP(m); pagezero(va); + m->md.pv_flags &= ~PV_MTE_TAGGED; } /* diff --git a/sys/arm64/include/cpu.h b/sys/arm64/include/cpu.h index 8d8a80a8d02a..d36e1e56c91c 100644 --- a/sys/arm64/include/cpu.h +++ b/sys/arm64/include/cpu.h @@ -284,6 +284,8 @@ void mte_copy_thread(struct thread *, struct thread *); void mte_thread_alloc(struct thread *); void mte_thread0(struct thread *); +void mte_sync_tags(vm_page_t page); + /* Functions to read the sanitised view of the special registers */ void update_special_regs(u_int); void update_special_reg_iss(u_int, uint64_t, uint64_t); diff --git a/sys/arm64/include/pmap.h b/sys/arm64/include/pmap.h index 69ae8e5c80b7..cf20827fa666 100644 --- a/sys/arm64/include/pmap.h +++ b/sys/arm64/include/pmap.h @@ -74,6 +74,9 @@ struct md_page { uint8_t pv_reserve[2]; }; +/* machine page flags */ +#define PV_MTE_TAGGED 0x01 /* page is tagged with MTE */ + enum pmap_stage { PM_INVALID, PM_STAGE1,home | help
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