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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1t5mFa-00000009uJi-1uF6; Tue, 29 Oct 2024 13:27:10 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id C86EB30073F; Tue, 29 Oct 2024 14:27:09 +0100 (CET) Date: Tue, 29 Oct 2024 14:27:09 +0100 From: Peter Zijlstra To: Josh Poimboeuf Cc: x86@kernel.org, Steven Rostedt , Ingo Molnar , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Indu Bhagat , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , linux-perf-users@vger.kernel.org, Mark Brown , linux-toolchains@vger.kernel.org, Jordan Rome , Sam James , linux-trace-kernel@vger.kerne.org, Andrii Nakryiko , Jens Remus , Mathieu Desnoyers , Florian Weimer , Andy Lutomirski Subject: Re: [PATCH v3 09/19] unwind: Introduce sframe user space unwinding Message-ID: <20241029132709.GY14555@noisy.programming.kicks-ass.net> References: <42c0a99236af65c09c8182e260af7bcf5aa1e158.1730150953.git.jpoimboe@kernel.org> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <42c0a99236af65c09c8182e260af7bcf5aa1e158.1730150953.git.jpoimboe@kernel.org> On Mon, Oct 28, 2024 at 02:47:36PM -0700, Josh Poimboeuf wrote: > +static int __sframe_add_section(unsigned long sframe_addr, > + unsigned long text_start, > + unsigned long text_end) > +{ > + struct maple_tree *sframe_mt = ¤t->mm->sframe_mt; > + struct sframe_section *sec; > + struct sframe_header shdr; > + unsigned long header_end; > + int ret; > + > + if (copy_from_user(&shdr, (void __user *)sframe_addr, sizeof(shdr))) > + return -EFAULT; > + > + if (shdr.preamble.magic != SFRAME_MAGIC || > + shdr.preamble.version != SFRAME_VERSION_2 || > + !(shdr.preamble.flags & SFRAME_F_FDE_SORTED) || > + shdr.auxhdr_len || !shdr.num_fdes || !shdr.num_fres || > + shdr.fdes_off > shdr.fres_off) { > + return -EINVAL; > + } > + > + sec = kmalloc(sizeof(*sec), GFP_KERNEL); > + if (!sec) > + return -ENOMEM; > + > + header_end = sframe_addr + SFRAME_HDR_SIZE(shdr); > + > + sec->sframe_addr = sframe_addr; > + sec->text_addr = text_start; > + sec->fdes_addr = header_end + shdr.fdes_off; > + sec->fres_addr = header_end + shdr.fres_off; > + sec->fdes_nr = shdr.num_fdes; > + sec->ra_off = shdr.cfa_fixed_ra_offset; > + sec->fp_off = shdr.cfa_fixed_fp_offset; > + > + ret = mtree_insert_range(sframe_mt, text_start, text_end, sec, GFP_KERNEL); > + if (ret) { > + kfree(sec); > + return ret; > + } > + > + return 0; > +} > + > +int sframe_add_section(unsigned long sframe_addr, unsigned long text_start, > + unsigned long text_end) > +{ > + struct mm_struct *mm = current->mm; > + struct vm_area_struct *sframe_vma; > + > + mmap_read_lock(mm); DEFINE_GUARD(mmap_read_lock, struct mm_struct *, mmap_read_lock(_T), mmap_read_unlock(_T)) in include/linux/mmap_lock.h ? > + > + sframe_vma = vma_lookup(mm, sframe_addr); > + if (!sframe_vma) > + goto err_unlock; > + > + if (text_start && text_end) { > + struct vm_area_struct *text_vma; > + > + text_vma = vma_lookup(mm, text_start); > + if (!(text_vma->vm_flags & VM_EXEC)) > + goto err_unlock; > + > + if (PAGE_ALIGN(text_end) != text_vma->vm_end) > + goto err_unlock; > + } else { > + struct vm_area_struct *vma, *text_vma = NULL; > + VMA_ITERATOR(vmi, mm, 0); > + > + for_each_vma(vmi, vma) { > + if (vma->vm_file != sframe_vma->vm_file || > + !(vma->vm_flags & VM_EXEC)) > + continue; > + > + if (text_vma) { > + pr_warn_once("%s[%d]: multiple EXEC segments unsupported\n", > + current->comm, current->pid); > + goto err_unlock; > + } > + > + text_vma = vma; > + } > + > + if (!text_vma) > + goto err_unlock; > + > + text_start = text_vma->vm_start; > + text_end = text_vma->vm_end; > + } > + > + mmap_read_unlock(mm); > + > + return __sframe_add_section(sframe_addr, text_start, text_end); > + > +err_unlock: > + mmap_read_unlock(mm); > + return -EINVAL; > +} > +int sframe_remove_section(unsigned long sframe_addr) > +{ > + struct mm_struct *mm = current->mm; > + struct sframe_section *sec; > + unsigned long index = 0; > + > + mt_for_each(&mm->sframe_mt, sec, index, ULONG_MAX) { > + if (sec->sframe_addr == sframe_addr) > + return __sframe_remove_section(mm, sec); > + } > + > + return -EINVAL; > +} > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -64,6 +64,7 @@ > #include > #include > #include > +#include > > #include > > @@ -2784,6 +2785,16 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, > case PR_RISCV_SET_ICACHE_FLUSH_CTX: > error = RISCV_SET_ICACHE_FLUSH_CTX(arg2, arg3); > break; > + case PR_ADD_SFRAME: > + if (arg5) > + return -EINVAL; > + error = sframe_add_section(arg2, arg3, arg4); > + break; > + case PR_REMOVE_SFRAME: > + if (arg3 || arg4 || arg5) > + return -EINVAL; > + error = sframe_remove_section(arg2); > + break; > default: > error = -EINVAL; > break; So I realize that mtree has an internal lock, but are we sure we don't want a lock around those prctl()s?