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Message-ID: <23ed6b8b-be53-bde0-717a-9eded1ad3780@loongson.cn>
Date: Sat, 20 May 2023 18:35:03 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: WANG Xuerui <kernel@...0n.name>,
Christian Brauner <brauner@...nel.org>,
Andy Lutomirski <luto@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Vincenzo Frascino <vincenzo.frascino@....com>,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH] LoongArch: Add support to clone a time namespace
On 05/18/2023 10:25 AM, Huacai Chen wrote:
> Hi, Tiezhu,
>
> The layout of vdso data (loongarch_vdso_data):
>
> struct vdso_pcpu_data pdata[NR_CPUS];
> struct vdso_data data[CS_BASES];
>
> VDSO_DATA_SIZE is the page aligned size of loongarch_vdso_data, and in
> memory, vdso code is above vdso data.
>
> Then, get_vdso_base() returns the start of vdso code, and
> get_vdso_data() returns the start of vdso data.
>
> In your patch, __arch_get_timens_vdso_data() returns get_vdso_data() +
> PAGE_SIZE, but you don't increase the size of loongarch_vdso_data. The
> result is it returns an address in vdso code.
>
> Now, do you know what the problem is? Or still insist that "I have tested"?
Please review the following changes based on the current patch,
modify the layout of vvar to expand a page size for timens_data,
and also map it to zero pfn before creating time namespace, then
the last thing is to add the callback function vvar_fault().
$ git diff
diff --git a/arch/loongarch/include/asm/page.h
b/arch/loongarch/include/asm/page.h
index fb5338b..26e8dcc 100644
--- a/arch/loongarch/include/asm/page.h
+++ b/arch/loongarch/include/asm/page.h
@@ -81,6 +81,7 @@ typedef struct { unsigned long pgprot; } pgprot_t;
#define __va(x) ((void *)((unsigned long)(x) +
PAGE_OFFSET - PHYS_OFFSET))
#define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT)
+#define sym_to_pfn(x) __phys_to_pfn(__pa_symbol(x))
#define virt_to_pfn(kaddr) PFN_DOWN(PHYSADDR(kaddr))
#define virt_to_page(kaddr) pfn_to_page(virt_to_pfn(kaddr))
diff --git a/arch/loongarch/kernel/vdso.c b/arch/loongarch/kernel/vdso.c
index cf62103..3e89aca 100644
--- a/arch/loongarch/kernel/vdso.c
+++ b/arch/loongarch/kernel/vdso.c
@@ -23,7 +23,27 @@
#include <vdso/vsyscall.h>
#include <generated/vdso-offsets.h>
+/*
+ * The layout of vvar:
+ *
+ * high
+ * +----------------+----------------+
+ * | timens_data | PAGE_SIZE |
+ * +----------------+----------------+
+ * | vdso_data | |
+ * | vdso_pcpu_data | VDSO_DATA_SIZE |
+ * +----------------+----------------+
+ * low
+ */
+#define VVAR_SIZE (VDSO_DATA_SIZE + PAGE_SIZE)
+
+enum vvar_pages {
+ VVAR_DATA_PAGE_OFFSET,
+ VVAR_TIMENS_PAGE_OFFSET,
+};
+
extern char vdso_start[], vdso_end[];
+extern unsigned long zero_pfn;
/* Kernel-provided data used by the VDSO. */
static union {
@@ -42,6 +62,40 @@ static int vdso_mremap(const struct
vm_special_mapping *sm, struct vm_area_struc
return 0;
}
+static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
+ struct vm_area_struct *vma, struct vm_fault
*vmf)
+{
+ struct page *timens_page = find_timens_vvar_page(vma);
+ unsigned long pfn;
+
+ switch (vmf->pgoff) {
+ case VVAR_DATA_PAGE_OFFSET:
+ if (timens_page)
+ pfn = page_to_pfn(timens_page);
+ else
+ pfn = sym_to_pfn(vdso_data);
+ break;
+#ifdef CONFIG_TIME_NS
+ case VVAR_TIMENS_PAGE_OFFSET:
+ /*
+ * If a task belongs to a time namespace then a namespace
+ * specific VVAR is mapped with the
VVAR_DATA_PAGE_OFFSET and
+ * the real VVAR page is mapped with the
VVAR_TIMENS_PAGE_OFFSET
+ * offset.
+ * See also the comment near timens_setup_vdso_data().
+ */
+ if (!timens_page)
+ return VM_FAULT_SIGBUS;
+ pfn = sym_to_pfn(vdso_data);
+ break;
+#endif /* CONFIG_TIME_NS */
+ default:
+ return VM_FAULT_SIGBUS;
+ }
+
+ return vmf_insert_pfn(vma, vmf->address, pfn);
+}
+
struct loongarch_vdso_info vdso_info = {
.vdso = vdso_start,
.size = PAGE_SIZE,
@@ -52,6 +106,7 @@ struct loongarch_vdso_info vdso_info = {
},
.data_mapping = {
.name = "[vvar]",
+ .fault = vvar_fault,
},
.offset_sigreturn = vdso_offset_sigreturn,
};
@@ -120,7 +175,7 @@ static unsigned long vdso_base(void)
int arch_setup_additional_pages(struct linux_binprm *bprm, int
uses_interp)
{
int ret;
- unsigned long vvar_size, size, data_addr, vdso_addr;
+ unsigned long size, data_addr, vdso_addr;
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
struct loongarch_vdso_info *info = current->thread.vdso;
@@ -132,17 +187,16 @@ int arch_setup_additional_pages(struct
linux_binprm *bprm, int uses_interp)
* Determine total area size. This includes the VDSO data itself
* and the data pages.
*/
- vvar_size = VDSO_DATA_SIZE;
- size = vvar_size + info->size;
+ size = VVAR_SIZE + info->size;
data_addr = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
if (IS_ERR_VALUE(data_addr)) {
ret = data_addr;
goto out;
}
- vdso_addr = data_addr + VDSO_DATA_SIZE;
+ vdso_addr = data_addr + VVAR_SIZE;
- vma = _install_special_mapping(mm, data_addr, vvar_size,
+ vma = _install_special_mapping(mm, data_addr, VVAR_SIZE,
VM_READ | VM_MAYREAD,
&info->data_mapping);
if (IS_ERR(vma)) {
@@ -153,7 +207,12 @@ int arch_setup_additional_pages(struct linux_binprm
*bprm, int uses_interp)
/* Map VDSO data page. */
ret = remap_pfn_range(vma, data_addr,
virt_to_phys(&loongarch_vdso_data) >>
PAGE_SHIFT,
- vvar_size, PAGE_READONLY);
+ VDSO_DATA_SIZE, PAGE_READONLY);
+ if (ret)
+ goto out;
+
+ ret = remap_pfn_range(vma, data_addr + VDSO_DATA_SIZE, zero_pfn,
+ PAGE_SIZE, PAGE_READONLY);
if (ret)
goto out;
If you have any more comments, please let me know, thank you.
I will send v2 after waiting for some more feedbacks.
Thanks,
Tiezhu
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