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Date: Sat, 21 Nov 2020 20:10:16 -0800 From: Andy Lutomirski <luto@...nel.org> To: Rick Edgecombe <rick.p.edgecombe@...el.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Jessica Yu <jeyu@...nel.org>, bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrew Lutomirski <luto@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Peter Zijlstra <peterz@...radead.org>, X86 ML <x86@...nel.org>, Mike Rapoport <rppt@...nel.org>, Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Dan Williams <dan.j.williams@...el.com>, Elena Reshetova <elena.reshetova@...el.com>, Weiny Ira <ira.weiny@...el.com> Subject: Re: [PATCH RFC 01/10] vmalloc: Add basic perm alloc implementation On Fri, Nov 20, 2020 at 12:30 PM Rick Edgecombe <rick.p.edgecombe@...el.com> wrote: > > In order to allow for future arch specific optimizations for vmalloc > permissions, first add an implementation of a new interface that will > work cross arch by using the existing set_memory_() functions. > > When allocating some memory that will be RO, for example it should be used > like: > > /* Reserve va */ > struct perm_allocation *alloc = perm_alloc(vstart, vend, page_cnt, PERM_R); I'm sure I could reverse-engineer this from the code, but: Where do vstart and vend come from? Does perm_alloc() allocate memory or just virtual addresses? Is the caller expected to call vmalloc()? How does one free this thing? > unsigned long ro = (unsigned long)perm_alloc_address(alloc); > > /* Write to writable address */ > strcpy((char *)perm_writable_addr(alloc, ro), "Some data to be RO"); > /* Signal that writing is done and mapping should be live */ > perm_writable_finish(alloc); > /* Print from RO address */ > printk("Read only data is: %s\n", (char *)ro); >
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