arm64: compat: VDSO setup for compat layer

If CONFIG_GENERIC_COMPAT_VDSO is enabled, compat vDSO is installed in a
compat (32 bit) process instead of sigpage.

Add the necessary code to setup the vDSO required pages.
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Shijith Thotton <sthotton@marvell.com>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Huw Davies <huw@codeweavers.com>
Link: https://lkml.kernel.org/r/20190621095252.32307-13-vincenzo.frascino@arm.com

arch/arm64/kernel/vdso.c

@@ -29,12 +29,22 @@
 #include <asm/vdso.h>
 
 extern char vdso_start[], vdso_end[];
+#ifdef CONFIG_COMPAT_VDSO
+extern char vdso32_start[], vdso32_end[];
+#endif /* CONFIG_COMPAT_VDSO */
 
 /* vdso_lookup arch_index */
 enum arch_vdso_type {
 	ARM64_VDSO = 0,
+#ifdef CONFIG_COMPAT_VDSO
+	ARM64_VDSO32 = 1,
+#endif /* CONFIG_COMPAT_VDSO */
 };
+#ifdef CONFIG_COMPAT_VDSO
+#define VDSO_TYPES		(ARM64_VDSO32 + 1)
+#else
 #define VDSO_TYPES		(ARM64_VDSO + 1)
+#endif /* CONFIG_COMPAT_VDSO */
 
 struct __vdso_abi {
 	const char *name;
@@ -53,6 +63,13 @@ static struct __vdso_abi vdso_lookup[VDSO_TYPES] __ro_after_init = {
 		.vdso_code_start = vdso_start,
 		.vdso_code_end = vdso_end,
 	},
+#ifdef CONFIG_COMPAT_VDSO
+	{
+		.name = "vdso32",
+		.vdso_code_start = vdso32_start,
+		.vdso_code_end = vdso32_end,
+	},
+#endif /* CONFIG_COMPAT_VDSO */
 };
 
 /*
@@ -163,24 +180,52 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
 /*
  * Create and map the vectors page for AArch32 tasks.
  */
+#ifdef CONFIG_COMPAT_VDSO
+static int aarch32_vdso_mremap(const struct vm_special_mapping *sm,
+		struct vm_area_struct *new_vma)
+{
+	return __vdso_remap(ARM64_VDSO32, sm, new_vma);
+}
+#endif /* CONFIG_COMPAT_VDSO */
+
 /*
  * aarch32_vdso_pages:
  * 0 - kuser helpers
  * 1 - sigreturn code
+ * or (CONFIG_COMPAT_VDSO):
+ * 0 - kuser helpers
+ * 1 - vdso data
+ * 2 - vdso code
  */
 #define C_VECTORS	0
+#ifdef CONFIG_COMPAT_VDSO
+#define C_VVAR		1
+#define C_VDSO		2
+#define C_PAGES		(C_VDSO + 1)
+#else
 #define C_SIGPAGE	1
 #define C_PAGES		(C_SIGPAGE + 1)
+#endif /* CONFIG_COMPAT_VDSO */
 static struct page *aarch32_vdso_pages[C_PAGES] __ro_after_init;
-static const struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
+static struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
 	{
 		.name	= "[vectors]", /* ABI */
 		.pages	= &aarch32_vdso_pages[C_VECTORS],
 	},
+#ifdef CONFIG_COMPAT_VDSO
+	{
+		.name = "[vvar]",
+	},
+	{
+		.name = "[vdso]",
+		.mremap = aarch32_vdso_mremap,
+	},
+#else
 	{
 		.name	= "[sigpage]", /* ABI */
 		.pages	= &aarch32_vdso_pages[C_SIGPAGE],
 	},
+#endif /* CONFIG_COMPAT_VDSO */
 };
 
 static int aarch32_alloc_kuser_vdso_page(void)
@@ -203,7 +248,33 @@ static int aarch32_alloc_kuser_vdso_page(void)
 	return 0;
 }
 
-static int __init aarch32_alloc_vdso_pages(void)
+#ifdef CONFIG_COMPAT_VDSO
+static int __aarch32_alloc_vdso_pages(void)
+{
+	int ret;
+
+	vdso_lookup[ARM64_VDSO32].dm = &aarch32_vdso_spec[C_VVAR];
+	vdso_lookup[ARM64_VDSO32].cm = &aarch32_vdso_spec[C_VDSO];
+
+	ret = __vdso_init(ARM64_VDSO32);
+	if (ret)
+		return ret;
+
+	ret = aarch32_alloc_kuser_vdso_page();
+	if (ret) {
+		unsigned long c_vvar =
+			(unsigned long)page_to_virt(aarch32_vdso_pages[C_VVAR]);
+		unsigned long c_vdso =
+			(unsigned long)page_to_virt(aarch32_vdso_pages[C_VDSO]);
+
+		free_page(c_vvar);
+		free_page(c_vdso);
+	}
+
+	return ret;
+}
+#else
+static int __aarch32_alloc_vdso_pages(void)
 {
 	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
 	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
@@ -224,6 +295,12 @@ static int __init aarch32_alloc_vdso_pages(void)
 
 	return ret;
 }
+#endif /* CONFIG_COMPAT_VDSO */
+
+static int __init aarch32_alloc_vdso_pages(void)
+{
+	return __aarch32_alloc_vdso_pages();
+}
 arch_initcall(aarch32_alloc_vdso_pages);
 
 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
@@ -245,6 +322,7 @@ static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
 	return PTR_ERR_OR_ZERO(ret);
 }
 
+#ifndef CONFIG_COMPAT_VDSO
 static int aarch32_sigreturn_setup(struct mm_struct *mm)
 {
 	unsigned long addr;
@@ -272,6 +350,7 @@ static int aarch32_sigreturn_setup(struct mm_struct *mm)
 out:
 	return PTR_ERR_OR_ZERO(ret);
 }
+#endif /* !CONFIG_COMPAT_VDSO */
 
 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 {
@@ -285,7 +364,14 @@ int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	if (ret)
 		goto out;
 
+#ifdef CONFIG_COMPAT_VDSO
+	ret = __setup_additional_pages(ARM64_VDSO32,
+				       mm,
+				       bprm,
+				       uses_interp);
+#else
 	ret = aarch32_sigreturn_setup(mm);
+#endif /* CONFIG_COMPAT_VDSO */
 
 out:
 	up_write(&mm->mmap_sem);