[PATCH, RFC] um: remove set_fs

* [PATCH, RFC] um: remove set_fs
@ 2021-07-09 13:38 Christoph Hellwig
  2021-07-09 14:47 ` Johannes Berg
  0 siblings, 1 reply; 12+ messages in thread
From: Christoph Hellwig @ 2021-07-09 13:38 UTC (permalink / raw)
  To: richard, anton.ivanov; +Cc: linux-um

Remove address space overrides using set_fs() for user mode Linux.

Compile tested only.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/um/Kconfig                   |  1 -
 arch/um/include/asm/thread_info.h |  4 ----
 arch/um/include/asm/uaccess.h     | 21 +++++++++++++++++++--
 arch/um/kernel/skas/uaccess.c     | 23 -----------------------
 arch/x86/um/asm/segment.h         |  8 --------
 5 files changed, 19 insertions(+), 38 deletions(-)

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 57cfd9a1c082..2a87f46259c8 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -19,7 +19,6 @@ config UML
 	select GENERIC_IRQ_SHOW
 	select GENERIC_CPU_DEVICES
 	select HAVE_GCC_PLUGINS
-	select SET_FS
 	select TTY # Needed for line.c
 
 config MMU
diff --git a/arch/um/include/asm/thread_info.h b/arch/um/include/asm/thread_info.h
index 3b1cb8b3b186..1395cbd7e340 100644
--- a/arch/um/include/asm/thread_info.h
+++ b/arch/um/include/asm/thread_info.h
@@ -22,9 +22,6 @@ struct thread_info {
 	__u32			cpu;		/* current CPU */
 	int			preempt_count;  /* 0 => preemptable,
 						   <0 => BUG */
-	mm_segment_t		addr_limit;	/* thread address space:
-					 	   0-0xBFFFFFFF for user
-						   0-0xFFFFFFFF for kernel */
 	struct thread_info	*real_thread;    /* Points to non-IRQ stack */
 	unsigned long aux_fp_regs[FP_SIZE];	/* auxiliary fp_regs to save/restore
 						   them out-of-band */
@@ -36,7 +33,6 @@ struct thread_info {
 	.flags =		0,		\
 	.cpu =		0,			\
 	.preempt_count = INIT_PREEMPT_COUNT,	\
-	.addr_limit =	KERNEL_DS,		\
 	.real_thread = NULL,			\
 }
 
diff --git a/arch/um/include/asm/uaccess.h b/arch/um/include/asm/uaccess.h
index fe66d659acad..85e0275c714b 100644
--- a/arch/um/include/asm/uaccess.h
+++ b/arch/um/include/asm/uaccess.h
@@ -8,6 +8,7 @@
 #define __UM_UACCESS_H
 
 #include <asm/elf.h>
+#include <asm/unaligned.h>
 
 #define __under_task_size(addr, size) \
 	(((unsigned long) (addr) < TASK_SIZE) && \
@@ -42,8 +43,24 @@ static inline int __access_ok(unsigned long addr, unsigned long size)
 {
 	return __addr_range_nowrap(addr, size) &&
 		(__under_task_size(addr, size) ||
-		__access_ok_vsyscall(addr, size) ||
-		uaccess_kernel());
+		 __access_ok_vsyscall(addr, size));
 }
 
+/* no pagefaults for kernel addresses in um */
+#define HAVE_GET_KERNEL_NOFAULT 1
+
+#define __get_kernel_nofault(dst, src, type, err_label)			\
+do {									\
+	*((type *)dst) = get_unaligned((type *)(src));			\
+	if (0) /* make sure the label looks used to the compiler */	\
+		goto err_label;						\
+} while (0)
+
+#define __put_kernel_nofault(dst, src, type, err_label)			\
+do {									\
+	put_unaligned(*((type *)src), (type *)(dst));			\
+	if (0) /* make sure the label looks used to the compiler */	\
+		goto err_label;						\
+} while (0)
+
 #endif
diff --git a/arch/um/kernel/skas/uaccess.c b/arch/um/kernel/skas/uaccess.c
index 2dec915abe6f..f716ba0e66ee 100644
--- a/arch/um/kernel/skas/uaccess.c
+++ b/arch/um/kernel/skas/uaccess.c
@@ -145,11 +145,6 @@ static int copy_chunk_from_user(unsigned long from, int len, void *arg)
 
 unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	if (uaccess_kernel()) {
-		memcpy(to, (__force void*)from, n);
-		return 0;
-	}
-
 	return buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to);
 }
 EXPORT_SYMBOL(raw_copy_from_user);
@@ -165,11 +160,6 @@ static int copy_chunk_to_user(unsigned long to, int len, void *arg)
 
 unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	if (uaccess_kernel()) {
-		memcpy((__force void *) to, from, n);
-		return 0;
-	}
-
 	return buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from);
 }
 EXPORT_SYMBOL(raw_copy_to_user);
@@ -193,11 +183,6 @@ long __strncpy_from_user(char *dst, const char __user *src, long count)
 	long n;
 	char *ptr = dst;
 
-	if (uaccess_kernel()) {
-		strncpy(dst, (__force void *) src, count);
-		return strnlen(dst, count);
-	}
-
 	n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
 		      &ptr);
 	if (n != 0)
@@ -214,11 +199,6 @@ static int clear_chunk(unsigned long addr, int len, void *unused)
 
 unsigned long __clear_user(void __user *mem, unsigned long len)
 {
-	if (uaccess_kernel()) {
-		memset((__force void*)mem, 0, len);
-		return 0;
-	}
-
 	return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
 }
 EXPORT_SYMBOL(__clear_user);
@@ -239,9 +219,6 @@ long __strnlen_user(const void __user *str, long len)
 {
 	int count = 0, n;
 
-	if (uaccess_kernel())
-		return strnlen((__force char*)str, len) + 1;
-
 	n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
 	if (n == 0)
 		return count + 1;
diff --git a/arch/x86/um/asm/segment.h b/arch/x86/um/asm/segment.h
index 453db377150d..2ef507bc6989 100644
--- a/arch/x86/um/asm/segment.h
+++ b/arch/x86/um/asm/segment.h
@@ -8,12 +8,4 @@ extern int host_gdt_entry_tls_min;
 #define GDT_ENTRY_TLS_MIN host_gdt_entry_tls_min
 #define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
 
-typedef struct {
-	unsigned long seg;
-} mm_segment_t;
-
-#define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
-#define KERNEL_DS	MAKE_MM_SEG(~0UL)
-#define USER_DS		MAKE_MM_SEG(TASK_SIZE)
-
 #endif
-- 
2.30.2


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