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t=1789733399; bh=3Dehqwl8OGnNMvcjzS5vLDo1ZS/hlXfR5Zt4WV//DR0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=clNlP/xGNon7MI8X0RjFpqvHuijI7yEviOueWkwQNnOTpUBtP0pbS9wIjxljNYqRU +QVzNz+3n0uAYKkQP0jJ97EYpcKgrs8BwsxaD/W1oGuLVMGjv9JcVoGH3bVOnWDpXG 41S624vt1Z9GU/9sG6gKST+Pl/dSR+8fTSh76gwlQlkWDjOIlBl+pRsJSLNoOpHDAS YSdpL2ltenZ3wQD1k4fLqpWaHRSRX3ri0qQRmL/YCc2u/ldqY+s0K+tRgBCA7ZHwVK SwdMKABhOtCpc9oyOImFGdzGXroxWLxMj+kS4i928FZc/EapKOMrS1cYPD8+kGZnj0 BeyFnnNNj9Qjg== Message-ID: <0b276f0a-39b7-46ae-b72f-6ba92f65380f@kernel.org> Date: Fri, 18 Sep 2026 14:09:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v8 1/5] mm: Add copy_remote_mm_str() To: Anastasios Papagiannis , bpf@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, andrii@kernel.org, ast@kernel.org, brauner@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, kpsingh@kernel.org, ljs@kernel.org, matt@bobrowski.net, memxor@gmail.com, song@kernel.org, sun.jian.kdev@gmail.com, utilityemal77@gmail.com, viro@zeniv.linux.org.uk References: <20260918091058.297740-1-tasos.papagiannnis@gmail.com> <20260918091058.297740-2-tasos.papagiannnis@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E384718000D X-Stat-Signature: z1h6bnczhs3uewwc6aho9if53wxfhsji X-HE-Tag: 1789733399-32653 X-HE-Meta: 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 9QxUXh1O En02f+wcGe0zBuenBcmkDBd6MOOjhO/G9xs/fRPYz0XBpJCIlgAKMydXoGZBdGb80HL8S0yC5pMLhvoMyHr1tLf8oer1539q0ycTmLZFhp2Z59YP/nHJeXHzlnZGPbM8dtWT0KT/VBokuZdQjU3+rklPD9V4F0tI+5Prs1/nJ95Tb5kcjXydTWS6BY701xElVqC7bPDO5S4dJrihbQTGr4OzKm9/eTqVtV7OVQ/5/jmRbPUfUwidS1XV8PVBQevUhnBFbgRaj1Cv8GBrXUARPTaxKL/UbNoamDEjH5MYqQJUHn3Oo62RHU4Sn18eRGw4MeZZQy4WGS+iUYbxp6p9jPhpooBIX6JoT0/+MQuf+fatg9eMMF7W28UrUy8NT7U17f4BXP1BiuzseNjP3E8G+oArln7Uy+ARXveVGR7Xq+wo6kZQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/18/26 11:10, Anastasios Papagiannis wrote: > copy_remote_vm_str() gets the target address space from a struct > task_struct. This does not work for an address space that exists but is > not yet associated with a task_struct, such as the mm held by struct > linux_binprm during exec. > > Add copy_remote_mm_str(), which operates directly on a struct mm_struct. > > Use a common internal interface for the MMU and NOMMU implementations > and define both public wrappers in mm/util.c. Preserve the existing > copy_remote_vm_str() behavior, including handling zero-length requests > before acquiring the task's mm. > > Signed-off-by: Anastasios Papagiannis > Acked-by: Lorenzo Stoakes (ARM) > Acked-by: David Hildenbrand (Arm) > --- > include/linux/mm.h | 8 +++--- > mm/internal.h | 3 +++ > mm/memory.c | 43 ++------------------------------ > mm/nommu.c | 43 ++------------------------------ > mm/util.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++ > 5 files changed, 73 insertions(+), 86 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index dd09c438fa23..63f40e615754 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3325,10 +3325,10 @@ extern int access_process_vm(struct task_struct *tsk, unsigned long addr, > extern int access_remote_vm(struct mm_struct *mm, unsigned long addr, > void *buf, int len, unsigned int gup_flags); > > -#ifdef CONFIG_BPF_SYSCALL > -extern int copy_remote_vm_str(struct task_struct *tsk, unsigned long addr, > - void *buf, int len, unsigned int gup_flags); > -#endif > +int copy_remote_mm_str(struct mm_struct *mm, unsigned long addr, > + void *buf, int len, unsigned int gup_flags); > +int copy_remote_vm_str(struct task_struct *tsk, unsigned long addr, > + void *buf, int len, unsigned int gup_flags); > > long get_user_pages_remote(struct mm_struct *mm, > unsigned long start, unsigned long nr_pages, > diff --git a/mm/internal.h b/mm/internal.h > index 38b1165212c9..557b29381355 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -25,6 +25,9 @@ > struct folio_batch; > struct hstate; > > +int __copy_remote_mm_str(struct mm_struct *mm, unsigned long addr, > + void *buf, int len, unsigned int gup_flags); Two tabs please. (I thought I commented on that already) > + > struct huge_bootmem_page { > struct list_head list; > struct hstate *hstate; > diff --git a/mm/memory.c b/mm/memory.c > index 8b0c2c735d3d..fc6933d7e9d3 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -7326,13 +7326,12 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, > } > EXPORT_SYMBOL_GPL(access_process_vm); > > -#ifdef CONFIG_BPF_SYSCALL > /* > * Copy a string from another process's address space as given in mm. > * If there is any error return -EFAULT. > */ > -static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, > - void *buf, int len, unsigned int gup_flags) > +int __copy_remote_mm_str(struct mm_struct *mm, unsigned long addr, > + void *buf, int len, unsigned int gup_flags) > { > void *old_buf = buf; > int err = 0; > @@ -7408,44 +7407,6 @@ static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, > return buf - old_buf; > } > > -/** > - * copy_remote_vm_str - copy a string from another process's address space. > - * @tsk: the task of the target address space > - * @addr: start address to read from > - * @buf: destination buffer > - * @len: number of bytes to copy > - * @gup_flags: flags modifying lookup behaviour > - * > - * The caller must hold a reference on @mm. > - * > - * Return: number of bytes copied from @addr (source) to @buf (destination); > - * not including the trailing NUL. Always guaranteed to leave NUL-terminated > - * buffer. On any error, return -EFAULT. > - */ > -int copy_remote_vm_str(struct task_struct *tsk, unsigned long addr, > - void *buf, int len, unsigned int gup_flags) Dito. > -{ > - struct mm_struct *mm; > - int ret; > - > - if (unlikely(len == 0)) > - return 0; > - > - mm = get_task_mm(tsk); > - if (!mm) { > - *(char *)buf = '\0'; > - return -EFAULT; > - } > - > - ret = __copy_remote_vm_str(mm, addr, buf, len, gup_flags); > - > - mmput(mm); > - > - return ret; > -} > -EXPORT_SYMBOL_GPL(copy_remote_vm_str); > -#endif /* CONFIG_BPF_SYSCALL */ > - > /* > * Print the name of a VMA. > */ > diff --git a/mm/nommu.c b/mm/nommu.c > index 498e01ee40b0..9a810c35e7e9 100644 > --- a/mm/nommu.c > +++ b/mm/nommu.c > @@ -1741,13 +1741,12 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in > } > EXPORT_SYMBOL_GPL(access_process_vm); > > -#ifdef CONFIG_BPF_SYSCALL > /* > * Copy a string from another process's address space as given in mm. > * If there is any error return -EFAULT. > */ > -static int __copy_remote_vm_str(struct mm_struct *mm, unsigned long addr, > - void *buf, int len) > +int __copy_remote_mm_str(struct mm_struct *mm, unsigned long addr, > + void *buf, int len, unsigned int gup_flags) Dito. I really couldn't care less about the pedantic doc things from the bpf bot. -- Cheers, David