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From: Benjamin Berg <benjamin@sipsolutions.net>
To: linux-um@lists.infradead.org
Cc: Benjamin Berg <benjamin@sipsolutions.net>
Subject: [PATCH 14/27] um: Create signal stack memory assignment in stub_data
Date: Wed,  3 Mar 2021 16:55:10 +0100	[thread overview]
Message-ID: <20210303155523.124277-15-benjamin@sipsolutions.net> (raw)
In-Reply-To: <20210303155523.124277-1-benjamin@sipsolutions.net>

When we switch to use seccomp, we need both the signal stack and other
data (i.e. syscall information) to co-exist in the stub data. To
facilitate this, start by defining separate memory areas for the stack
and syscall data.

Only change the signal stack setup for now, as the syscall code will be
reworked later.

Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
---
 arch/um/include/shared/skas/stub-data.h | 12 ++++++++++++
 arch/um/kernel/skas/clone.c             |  5 ++++-
 arch/um/os-Linux/skas/process.c         |  9 ++++++++-
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h
index 5e3ade3fb38b..2d5da12679ad 100644
--- a/arch/um/include/shared/skas/stub-data.h
+++ b/arch/um/include/shared/skas/stub-data.h
@@ -8,10 +8,22 @@
 #ifndef __STUB_DATA_H
 #define __STUB_DATA_H
 
+#include <linux/compiler_types.h>
+#include <as-layout.h>
+
 struct stub_data {
 	unsigned long offset;
 	int fd;
 	long parent_err, child_err;
+
+	/* 128 leaves enough room for additional fields in the struct. */
+	unsigned char syscall_data[UM_KERN_PAGE_SIZE - MINSIGSTKSZ - 128]
+		      __aligned(16);
+
+	/* Stack for our signal handlers and for calling into . */
+	unsigned char sigstack[MINSIGSTKSZ + 32] __aligned(16);
 };
 
+typedef char stub_data_sizecheck[sizeof(struct stub_data) <= UM_KERN_PAGE_SIZE ? 1 : -1] __always_unused;
+
 #endif
diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
index 592cdb138441..3e2139a81475 100644
--- a/arch/um/kernel/skas/clone.c
+++ b/arch/um/kernel/skas/clone.c
@@ -28,8 +28,11 @@ stub_clone_handler(void)
 	struct stub_data *data = (void *) ((unsigned long)&stack & ~(UM_KERN_PAGE_SIZE - 1));
 	long err;
 
+	/* Use the syscall data as a temporary stack area. */
 	err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD,
-			    (unsigned long)data + UM_KERN_PAGE_SIZE / 2 - sizeof(void *));
+			    (unsigned long) data->syscall_data +
+					    sizeof(data->syscall_data) -
+					    sizeof(void *));
 	if (err) {
 		data->parent_err = err;
 		goto done;
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 15818009731d..717cfe7400a1 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -204,6 +204,7 @@ extern char __syscall_stub_start[];
 static int userspace_tramp(void *stack)
 {
 	struct sigaction sa;
+	struct stub_data *data;
 	void *addr;
 	int fd;
 	unsigned long long offset;
@@ -234,8 +235,14 @@ static int userspace_tramp(void *stack)
 			STUB_DATA, errno);
 		exit(1);
 	}
+	data = (void *) addr;
+	/*
+	 * We need at least MINSIGSTKSZ for the kernel and glibc wants a bit more
+	 * But we cannot use BUILD_BUG_ON here.
+	 * BUILD_BUG_ON (sizeof(data->sigstack) >= MINSIGSTKSZ + sizeof(struct stack_t));
+	 */
 
-	set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
+	set_sigstack((void *) &data->sigstack, sizeof(data->sigstack));
 	sigemptyset(&sa.sa_mask);
 	sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
 	sa.sa_sigaction = (void *) segv_handler;
-- 
2.29.2


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  parent reply	other threads:[~2021-03-03 16:02 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-03 15:54 [PATCH 00/27] Implement SECCOMP based userland Benjamin Berg
2021-03-03 15:54 ` [PATCH 01/27] um: Switch printk calls to adhere to correct coding style Benjamin Berg
2021-03-03 15:54 ` [PATCH 02/27] um: Declare fix_range_common as a static function Benjamin Berg
2021-03-03 15:54 ` [PATCH 03/27] um: Drop support for hosts without SYSEMU_SINGLESTEP support Benjamin Berg
2021-06-19 20:17   ` Richard Weinberger
2021-06-20 12:05     ` Benjamin Berg
2021-03-03 15:55 ` [PATCH 04/27] um: Drop NULL check from start_userspace Benjamin Berg
2021-03-03 15:55 ` [PATCH 05/27] um: Make errors to stop ptraced child fatal during startup Benjamin Berg
2021-03-03 15:55 ` [PATCH 06/27] um: Don't use vfprintf() for os_info() Benjamin Berg
2021-03-03 15:55 ` [PATCH 07/27] um: Do not use printk in SIGWINCH helper thread Benjamin Berg
2021-03-03 15:55 ` [PATCH 08/27] um: Reap winch thread if it fails Benjamin Berg
2021-03-03 15:55 ` [PATCH 09/27] um: Do not use printk in userspace trampoline Benjamin Berg
2021-03-03 15:55 ` [PATCH 10/27] um: Always inline stub functions Benjamin Berg
2021-03-03 15:55 ` [PATCH 11/27] um: Rely on PTRACE_SETREGSET to set FS/GS base registers Benjamin Berg
2021-03-03 15:55 ` [PATCH 12/27] um: Remove unused register save/restore functions Benjamin Berg
2021-03-03 15:55 ` [PATCH 13/27] um: Mark 32bit syscall helpers as clobbering memory Benjamin Berg
2021-03-03 15:55 ` Benjamin Berg [this message]
2021-03-03 15:55 ` [PATCH 15/27] um: Add generic stub_syscall6 function Benjamin Berg
2021-03-03 15:55 ` [PATCH 16/27] um: Rework syscall handling Benjamin Berg
2021-03-03 15:55 ` [PATCH 17/27] um: Store full CSGSFS and SS register from mcontext Benjamin Berg
2021-03-03 15:55 ` [PATCH 18/27] um: Pass full mm_id to functions creating helper processes Benjamin Berg
2021-03-03 15:55 ` [PATCH 19/27] um: Move faultinfo extraction into userspace routine Benjamin Berg
2021-03-03 15:55 ` [PATCH 20/27] um: Use struct uml_pt_regs for copy_context_skas0 Benjamin Berg
2021-03-03 15:55 ` [PATCH 21/27] um: Add UML_SECCOMP configuration option Benjamin Berg
2021-03-03 15:55 ` [PATCH 22/27] um: Add stub side of SECCOMP/futex based process handling Benjamin Berg
2021-03-03 15:55 ` [PATCH 23/27] um: Add helper functions to get/set state for SECCOMP Benjamin Berg
2021-03-03 15:55 ` [PATCH 24/27] um: Add SECCOMP support detection and initialization Benjamin Berg
2021-03-03 15:55 ` [PATCH 25/27] um: Die if a child dies unexpectedly in seccomp mode Benjamin Berg
2021-03-03 15:55 ` [PATCH 26/27] um: Implement kernel side of SECCOMP based process handling Benjamin Berg
2021-03-03 15:55 ` [PATCH 27/27] um: Delay flushing syscalls until the thread is restarted Benjamin Berg

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