linux-kernel - [PATCH 18/19] arm64/vdso: Migrate native signals to user

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Message-Id: <20201108051730.2042693-19-dima@arista.com>
Date:   Sun,  8 Nov 2020 05:17:28 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Dmitry Safonov <dima@...sta.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Guo Ren <guoren@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Will Deacon <will@...nel.org>, x86@...nel.org
Subject: [PATCH 18/19] arm64/vdso: Migrate native signals to user_landing

Generic way to track the land vma area.
As a bonus, after unmapping vdso, kernel won't try to land on its
previous position.

Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
 arch/arm64/kernel/signal.c | 10 +++++++---
 arch/arm64/kernel/vdso.c   | 13 +++----------
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index bec6ef69704f..4c1dfbc1aed3 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -723,9 +723,10 @@ static int get_sigframe(struct rt_sigframe_user_layout *user,
 	return 0;
 }
 
-static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
+static int setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 			 struct rt_sigframe_user_layout *user, int usig)
 {
+	unsigned long land = (unsigned long)current->mm->user_landing;
 	__sigrestore_t sigtramp;
 
 	regs->regs[0] = usig;
@@ -754,10 +755,13 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 
 	if (ka->sa.sa_flags & SA_RESTORER)
 		sigtramp = ka->sa.sa_restorer;
+	else if (land != UNMAPPED_USER_LANDING)
+		sigtramp = VDSO_SYMBOL(land, sigtramp);
 	else
-		sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
+		return 1;
 
 	regs->regs[30] = (unsigned long)sigtramp;
+	return 0;
 }
 
 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
@@ -780,7 +784,7 @@ static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 	err |= setup_sigframe(&user, regs, set);
 	if (err == 0) {
-		setup_return(regs, &ksig->ka, &user, usig);
+		err = setup_return(regs, &ksig->ka, &user, usig);
 		if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 			err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 			regs->regs[1] = (unsigned long)&frame->info;
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 08e8f1d56d92..d710fcd7141c 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -78,12 +78,6 @@ static union {
 } vdso_data_store __page_aligned_data;
 struct vdso_data *vdso_data = vdso_data_store.data;
 
-static void vdso_mremap(const struct vm_special_mapping *sm,
-		struct vm_area_struct *new_vma)
-{
-	current->mm->context.vdso = (void *)new_vma->vm_start;
-}
-
 static int __vdso_init(enum vdso_abi abi)
 {
 	int i;
@@ -239,7 +233,6 @@ static int __setup_additional_pages(enum vdso_abi abi,
 		gp_flags = VM_ARM64_BTI;
 
 	vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
-	mm->context.vdso = (void *)vdso_base;
 	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 				       VM_READ|VM_EXEC|gp_flags|
 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
@@ -247,12 +240,14 @@ static int __setup_additional_pages(enum vdso_abi abi,
 	if (IS_ERR(ret))
 		goto up_fail;
 
+	/* 32-bit ABI is to land on sigpage, 64-bit on vdso */
+	if (abi == VDSO_ABI_AA64)
+		mm->user_landing = (void __user *)vdso_base;
 	*sysinfo_ehdr = vdso_base;
 
 	return 0;
 
 up_fail:
-	mm->context.vdso = NULL;
 	return PTR_ERR(ret);
 }
 
@@ -285,7 +280,6 @@ static struct vm_special_mapping aarch32_vdso_maps[] = {
 	},
 	[AA32_MAP_VDSO] = {
 		.name = "[vdso]",
-		.mremap = vdso_mremap,
 	},
 };
 
@@ -431,7 +425,6 @@ static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
 	},
 	[AA64_MAP_VDSO] = {
 		.name	= "[vdso]",
-		.mremap = vdso_mremap,
 	},
 };
 
-- 
2.28.0