[PATCH v4 05/11] s390: Change s390_kernel_write() return type to match memcpy()

[PATCH v4 05/11] s390: Change s390_kernel_write() return type to match memcpy()

[Josh Poimboeuf]

s390_kernel_write()'s function type is almost identical to memcpy().
Change its return type to "void *" so they can be used interchangeably.

Cc: linux-s390@vger.kernel.org
Cc: heiko.carstens@de.ibm.com
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
---
 arch/s390/include/asm/uaccess.h | 2 +-
 arch/s390/mm/maccess.c          | 9 ++++++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
index a470f1fa9f2a..324438889fe1 100644
--- a/arch/s390/include/asm/uaccess.h
+++ b/arch/s390/include/asm/uaccess.h
@@ -276,6 +276,6 @@ static inline unsigned long __must_check clear_user(void __user *to, unsigned lo
 }
 
 int copy_to_user_real(void __user *dest, void *src, unsigned long count);
-void s390_kernel_write(void *dst, const void *src, size_t size);
+void *s390_kernel_write(void *dst, const void *src, size_t size);
 
 #endif /* __S390_UACCESS_H */
diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
index de7ca4b6718f..22a0be655f27 100644
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -55,19 +55,22 @@ static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t siz
  */
 static DEFINE_SPINLOCK(s390_kernel_write_lock);
 
-void notrace s390_kernel_write(void *dst, const void *src, size_t size)
+notrace void *s390_kernel_write(void *dst, const void *src, size_t size)
 {
+	void *tmp = dst;
 	unsigned long flags;
 	long copied;
 
 	spin_lock_irqsave(&s390_kernel_write_lock, flags);
 	while (size) {
-		copied = s390_kernel_write_odd(dst, src, size);
-		dst += copied;
+		copied = s390_kernel_write_odd(tmp, src, size);
+		tmp += copied;
 		src += copied;
 		size -= copied;
 	}
 	spin_unlock_irqrestore(&s390_kernel_write_lock, flags);
+
+	return dst;
 }
 
 static int __no_sanitize_address __memcpy_real(void *dest, void *src, size_t count)
-- 
2.21.1

[PATCH v4 06/11] s390/module: Use s390_kernel_write() for late relocations

[Josh Poimboeuf]

From: Peter Zijlstra <peterz@infradead.org>

Because of late module patching, a livepatch module needs to be able to
apply some of its relocations well after it has been loaded.  Instead of
playing games with module_{dis,en}able_ro(), use existing text poking
mechanisms to apply relocations after module loading.

So far only x86, s390 and Power have HAVE_LIVEPATCH but only the first
two also have STRICT_MODULE_RWX.

This will allow removal of the last module_disable_ro() usage in
livepatch.  The ultimate goal is to completely disallow making
executable mappings writable.

[ jpoimboe: Split up patches.  Use mod state to determine whether
	    memcpy() can be used.  Test and add fixes. ]

Cc: linux-s390@vger.kernel.org
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
---
 arch/s390/kernel/module.c | 147 +++++++++++++++++++++++---------------
 1 file changed, 88 insertions(+), 59 deletions(-)

diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index ba8f19bb438b..4055f1c49814 100644
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -19,6 +19,7 @@
 #include <linux/kasan.h>
 #include <linux/moduleloader.h>
 #include <linux/bug.h>
+#include <linux/memory.h>
 #include <asm/alternative.h>
 #include <asm/nospec-branch.h>
 #include <asm/facility.h>
@@ -174,10 +175,12 @@ int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
 }
 
 static int apply_rela_bits(Elf_Addr loc, Elf_Addr val,
-			   int sign, int bits, int shift)
+			   int sign, int bits, int shift,
+			   void *(*write)(void *dest, const void *src, size_t len))
 {
 	unsigned long umax;
 	long min, max;
+	void *dest = (void *)loc;
 
 	if (val & ((1UL << shift) - 1))
 		return -ENOEXEC;
@@ -194,26 +197,33 @@ static int apply_rela_bits(Elf_Addr loc, Elf_Addr val,
 			return -ENOEXEC;
 	}
 
-	if (bits == 8)
-		*(unsigned char *) loc = val;
-	else if (bits == 12)
-		*(unsigned short *) loc = (val & 0xfff) |
+	if (bits == 8) {
+		unsigned char tmp = val;
+		write(dest, &tmp, 1);
+	} else if (bits == 12) {
+		unsigned short tmp = (val & 0xfff) |
 			(*(unsigned short *) loc & 0xf000);
-	else if (bits == 16)
-		*(unsigned short *) loc = val;
-	else if (bits == 20)
-		*(unsigned int *) loc = (val & 0xfff) << 16 |
-			(val & 0xff000) >> 4 |
-			(*(unsigned int *) loc & 0xf00000ff);
-	else if (bits == 32)
-		*(unsigned int *) loc = val;
-	else if (bits == 64)
-		*(unsigned long *) loc = val;
+		write(dest, &tmp, 2);
+	} else if (bits == 16) {
+		unsigned short tmp = val;
+		write(dest, &tmp, 2);
+	} else if (bits == 20) {
+		unsigned int tmp = (val & 0xfff) << 16 |
+			(val & 0xff000) >> 4 | (*(unsigned int *) loc & 0xf00000ff);
+		write(dest, &tmp, 4);
+	} else if (bits == 32) {
+		unsigned int tmp = val;
+		write(dest, &tmp, 4);
+	} else if (bits == 64) {
+		unsigned long tmp = val;
+		write(dest, &tmp, 8);
+	}
 	return 0;
 }
 
 static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
-		      const char *strtab, struct module *me)
+		      const char *strtab, struct module *me,
+		      void *(*write)(void *dest, const void *src, size_t len))
 {
 	struct mod_arch_syminfo *info;
 	Elf_Addr loc, val;
@@ -241,17 +251,17 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
 	case R_390_64:		/* Direct 64 bit.  */
 		val += rela->r_addend;
 		if (r_type == R_390_8)
-			rc = apply_rela_bits(loc, val, 0, 8, 0);
+			rc = apply_rela_bits(loc, val, 0, 8, 0, write);
 		else if (r_type == R_390_12)
-			rc = apply_rela_bits(loc, val, 0, 12, 0);
+			rc = apply_rela_bits(loc, val, 0, 12, 0, write);
 		else if (r_type == R_390_16)
-			rc = apply_rela_bits(loc, val, 0, 16, 0);
+			rc = apply_rela_bits(loc, val, 0, 16, 0, write);
 		else if (r_type == R_390_20)
-			rc = apply_rela_bits(loc, val, 1, 20, 0);
+			rc = apply_rela_bits(loc, val, 1, 20, 0, write);
 		else if (r_type == R_390_32)
-			rc = apply_rela_bits(loc, val, 0, 32, 0);
+			rc = apply_rela_bits(loc, val, 0, 32, 0, write);
 		else if (r_type == R_390_64)
-			rc = apply_rela_bits(loc, val, 0, 64, 0);
+			rc = apply_rela_bits(loc, val, 0, 64, 0, write);
 		break;
 	case R_390_PC16:	/* PC relative 16 bit.  */
 	case R_390_PC16DBL:	/* PC relative 16 bit shifted by 1.  */
@@ -260,15 +270,15 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
 	case R_390_PC64:	/* PC relative 64 bit.	*/
 		val += rela->r_addend - loc;
 		if (r_type == R_390_PC16)
-			rc = apply_rela_bits(loc, val, 1, 16, 0);
+			rc = apply_rela_bits(loc, val, 1, 16, 0, write);
 		else if (r_type == R_390_PC16DBL)
-			rc = apply_rela_bits(loc, val, 1, 16, 1);
+			rc = apply_rela_bits(loc, val, 1, 16, 1, write);
 		else if (r_type == R_390_PC32DBL)
-			rc = apply_rela_bits(loc, val, 1, 32, 1);
+			rc = apply_rela_bits(loc, val, 1, 32, 1, write);
 		else if (r_type == R_390_PC32)
-			rc = apply_rela_bits(loc, val, 1, 32, 0);
+			rc = apply_rela_bits(loc, val, 1, 32, 0, write);
 		else if (r_type == R_390_PC64)
-			rc = apply_rela_bits(loc, val, 1, 64, 0);
+			rc = apply_rela_bits(loc, val, 1, 64, 0, write);
 		break;
 	case R_390_GOT12:	/* 12 bit GOT offset.  */
 	case R_390_GOT16:	/* 16 bit GOT offset.  */
@@ -283,33 +293,33 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
 	case R_390_GOTPLT64:	/* 64 bit offset to jump slot.	*/
 	case R_390_GOTPLTENT:	/* 32 bit rel. offset to jump slot >> 1. */
 		if (info->got_initialized == 0) {
-			Elf_Addr *gotent;
+			Elf_Addr *gotent = me->core_layout.base +
+					   me->arch.got_offset +
+					   info->got_offset;
 
-			gotent = me->core_layout.base + me->arch.got_offset +
-				info->got_offset;
-			*gotent = val;
+			write(gotent, &val, sizeof(*gotent));
 			info->got_initialized = 1;
 		}
 		val = info->got_offset + rela->r_addend;
 		if (r_type == R_390_GOT12 ||
 		    r_type == R_390_GOTPLT12)
-			rc = apply_rela_bits(loc, val, 0, 12, 0);
+			rc = apply_rela_bits(loc, val, 0, 12, 0, write);
 		else if (r_type == R_390_GOT16 ||
 			 r_type == R_390_GOTPLT16)
-			rc = apply_rela_bits(loc, val, 0, 16, 0);
+			rc = apply_rela_bits(loc, val, 0, 16, 0, write);
 		else if (r_type == R_390_GOT20 ||
 			 r_type == R_390_GOTPLT20)
-			rc = apply_rela_bits(loc, val, 1, 20, 0);
+			rc = apply_rela_bits(loc, val, 1, 20, 0, write);
 		else if (r_type == R_390_GOT32 ||
 			 r_type == R_390_GOTPLT32)
-			rc = apply_rela_bits(loc, val, 0, 32, 0);
+			rc = apply_rela_bits(loc, val, 0, 32, 0, write);
 		else if (r_type == R_390_GOT64 ||
 			 r_type == R_390_GOTPLT64)
-			rc = apply_rela_bits(loc, val, 0, 64, 0);
+			rc = apply_rela_bits(loc, val, 0, 64, 0, write);
 		else if (r_type == R_390_GOTENT ||
 			 r_type == R_390_GOTPLTENT) {
 			val += (Elf_Addr) me->core_layout.base - loc;
-			rc = apply_rela_bits(loc, val, 1, 32, 1);
+			rc = apply_rela_bits(loc, val, 1, 32, 1, write);
 		}
 		break;
 	case R_390_PLT16DBL:	/* 16 bit PC rel. PLT shifted by 1.  */
@@ -320,25 +330,29 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
 	case R_390_PLTOFF32:	/* 32 bit offset from GOT to PLT. */
 	case R_390_PLTOFF64:	/* 16 bit offset from GOT to PLT. */
 		if (info->plt_initialized == 0) {
-			unsigned int *ip;
-			ip = me->core_layout.base + me->arch.plt_offset +
-				info->plt_offset;
-			ip[0] = 0x0d10e310;	/* basr 1,0  */
-			ip[1] = 0x100a0004;	/* lg	1,10(1) */
+			unsigned int insn[5];
+			unsigned int *ip = me->core_layout.base +
+					   me->arch.plt_offset +
+					   info->plt_offset;
+
+			insn[0] = 0x0d10e310;	/* basr 1,0  */
+			insn[1] = 0x100a0004;	/* lg	1,10(1) */
 			if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable) {
 				unsigned int *ij;
 				ij = me->core_layout.base +
 					me->arch.plt_offset +
 					me->arch.plt_size - PLT_ENTRY_SIZE;
-				ip[2] = 0xa7f40000 +	/* j __jump_r1 */
+				insn[2] = 0xa7f40000 +	/* j __jump_r1 */
 					(unsigned int)(u16)
 					(((unsigned long) ij - 8 -
 					  (unsigned long) ip) / 2);
 			} else {
-				ip[2] = 0x07f10000;	/* br %r1 */
+				insn[2] = 0x07f10000;	/* br %r1 */
 			}
-			ip[3] = (unsigned int) (val >> 32);
-			ip[4] = (unsigned int) val;
+			insn[3] = (unsigned int) (val >> 32);
+			insn[4] = (unsigned int) val;
+
+			write(ip, insn, sizeof(insn));
 			info->plt_initialized = 1;
 		}
 		if (r_type == R_390_PLTOFF16 ||
@@ -357,17 +371,17 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
 			val += rela->r_addend - loc;
 		}
 		if (r_type == R_390_PLT16DBL)
-			rc = apply_rela_bits(loc, val, 1, 16, 1);
+			rc = apply_rela_bits(loc, val, 1, 16, 1, write);
 		else if (r_type == R_390_PLTOFF16)
-			rc = apply_rela_bits(loc, val, 0, 16, 0);
+			rc = apply_rela_bits(loc, val, 0, 16, 0, write);
 		else if (r_type == R_390_PLT32DBL)
-			rc = apply_rela_bits(loc, val, 1, 32, 1);
+			rc = apply_rela_bits(loc, val, 1, 32, 1, write);
 		else if (r_type == R_390_PLT32 ||
 			 r_type == R_390_PLTOFF32)
-			rc = apply_rela_bits(loc, val, 0, 32, 0);
+			rc = apply_rela_bits(loc, val, 0, 32, 0, write);
 		else if (r_type == R_390_PLT64 ||
 			 r_type == R_390_PLTOFF64)
-			rc = apply_rela_bits(loc, val, 0, 64, 0);
+			rc = apply_rela_bits(loc, val, 0, 64, 0, write);
 		break;
 	case R_390_GOTOFF16:	/* 16 bit offset to GOT.  */
 	case R_390_GOTOFF32:	/* 32 bit offset to GOT.  */
@@ -375,20 +389,20 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
 		val = val + rela->r_addend -
 			((Elf_Addr) me->core_layout.base + me->arch.got_offset);
 		if (r_type == R_390_GOTOFF16)
-			rc = apply_rela_bits(loc, val, 0, 16, 0);
+			rc = apply_rela_bits(loc, val, 0, 16, 0, write);
 		else if (r_type == R_390_GOTOFF32)
-			rc = apply_rela_bits(loc, val, 0, 32, 0);
+			rc = apply_rela_bits(loc, val, 0, 32, 0, write);
 		else if (r_type == R_390_GOTOFF64)
-			rc = apply_rela_bits(loc, val, 0, 64, 0);
+			rc = apply_rela_bits(loc, val, 0, 64, 0, write);
 		break;
 	case R_390_GOTPC:	/* 32 bit PC relative offset to GOT. */
 	case R_390_GOTPCDBL:	/* 32 bit PC rel. off. to GOT shifted by 1. */
 		val = (Elf_Addr) me->core_layout.base + me->arch.got_offset +
 			rela->r_addend - loc;
 		if (r_type == R_390_GOTPC)
-			rc = apply_rela_bits(loc, val, 1, 32, 0);
+			rc = apply_rela_bits(loc, val, 1, 32, 0, write);
 		else if (r_type == R_390_GOTPCDBL)
-			rc = apply_rela_bits(loc, val, 1, 32, 1);
+			rc = apply_rela_bits(loc, val, 1, 32, 1, write);
 		break;
 	case R_390_COPY:
 	case R_390_GLOB_DAT:	/* Create GOT entry.  */
@@ -412,9 +426,10 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
 	return 0;
 }
 
-int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
+static int __apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 		       unsigned int symindex, unsigned int relsec,
-		       struct module *me)
+		       struct module *me,
+		       void *(*write)(void *dest, const void *src, size_t len))
 {
 	Elf_Addr base;
 	Elf_Sym *symtab;
@@ -430,13 +445,27 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 	n = sechdrs[relsec].sh_size / sizeof(Elf_Rela);
 
 	for (i = 0; i < n; i++, rela++) {
-		rc = apply_rela(rela, base, symtab, strtab, me);
+		rc = apply_rela(rela, base, symtab, strtab, me, write);
 		if (rc)
 			return rc;
 	}
 	return 0;
 }
 
+int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
+		       unsigned int symindex, unsigned int relsec,
+		       struct module *me)
+{
+	bool early = me->state == MODULE_STATE_UNFORMED;
+	void *(*write)(void *, const void *, size_t) = memcpy;
+
+	if (!early)
+		write = s390_kernel_write;
+
+	return __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
+				    write);
+}
+
 int module_finalize(const Elf_Ehdr *hdr,
 		    const Elf_Shdr *sechdrs,
 		    struct module *me)
-- 
2.21.1

Re: [PATCH v4 06/11] s390/module: Use s390_kernel_write() for late relocations

[Jiri Kosina]

On Wed, 29 Apr 2020, Josh Poimboeuf wrote:

> From: Peter Zijlstra <peterz@infradead.org>
> 
> Because of late module patching, a livepatch module needs to be able to
> apply some of its relocations well after it has been loaded.  Instead of
> playing games with module_{dis,en}able_ro(), use existing text poking
> mechanisms to apply relocations after module loading.
> 
> So far only x86, s390 and Power have HAVE_LIVEPATCH but only the first
> two also have STRICT_MODULE_RWX.
> 
> This will allow removal of the last module_disable_ro() usage in
> livepatch.  The ultimate goal is to completely disallow making
> executable mappings writable.
> 
> [ jpoimboe: Split up patches.  Use mod state to determine whether
> 	    memcpy() can be used.  Test and add fixes. ]
> 
> Cc: linux-s390@vger.kernel.org
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
> Acked-by: Miroslav Benes <mbenes@suse.cz>

Could we please get an Ack / Reviewed-by: for this patch from s390 folks?

Thanks,

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH v4 06/11] s390/module: Use s390_kernel_write() for late relocations

[Gerald Schaefer]

On Thu, 7 May 2020 12:00:13 +0200 (CEST)
Jiri Kosina <jikos@kernel.org> wrote:

> On Wed, 29 Apr 2020, Josh Poimboeuf wrote:
> 
> > From: Peter Zijlstra <peterz@infradead.org>
> > 
> > Because of late module patching, a livepatch module needs to be able to
> > apply some of its relocations well after it has been loaded.  Instead of
> > playing games with module_{dis,en}able_ro(), use existing text poking
> > mechanisms to apply relocations after module loading.
> > 
> > So far only x86, s390 and Power have HAVE_LIVEPATCH but only the first
> > two also have STRICT_MODULE_RWX.
> > 
> > This will allow removal of the last module_disable_ro() usage in
> > livepatch.  The ultimate goal is to completely disallow making
> > executable mappings writable.
> > 
> > [ jpoimboe: Split up patches.  Use mod state to determine whether
> > 	    memcpy() can be used.  Test and add fixes. ]
> > 
> > Cc: linux-s390@vger.kernel.org
> > Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> > Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
> > Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> > Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
> > Acked-by: Miroslav Benes <mbenes@suse.cz>
> 
> Could we please get an Ack / Reviewed-by: for this patch from s390 folks?
> 
> Thanks,
> 

Looks pretty straightforward, and using s390_kernel_write() is OK, so

Acked-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> # s390

Re: [PATCH v4 05/11] s390: Change s390_kernel_write() return type to match memcpy()

[Jiri Kosina]

On Wed, 29 Apr 2020, Josh Poimboeuf wrote:

> s390_kernel_write()'s function type is almost identical to memcpy().
> Change its return type to "void *" so they can be used interchangeably.
> 
> Cc: linux-s390@vger.kernel.org
> Cc: heiko.carstens@de.ibm.com
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
> Acked-by: Miroslav Benes <mbenes@suse.cz>

Also for this one -- s390 folks, could you please provide your Ack for 
taking things through livepatching.git as part of this series?

Thanks.

> ---
>  arch/s390/include/asm/uaccess.h | 2 +-
>  arch/s390/mm/maccess.c          | 9 ++++++---
>  2 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h
> index a470f1fa9f2a..324438889fe1 100644
> --- a/arch/s390/include/asm/uaccess.h
> +++ b/arch/s390/include/asm/uaccess.h
> @@ -276,6 +276,6 @@ static inline unsigned long __must_check clear_user(void __user *to, unsigned lo
>  }
>  
>  int copy_to_user_real(void __user *dest, void *src, unsigned long count);
> -void s390_kernel_write(void *dst, const void *src, size_t size);
> +void *s390_kernel_write(void *dst, const void *src, size_t size);
>  
>  #endif /* __S390_UACCESS_H */
> diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
> index de7ca4b6718f..22a0be655f27 100644
> --- a/arch/s390/mm/maccess.c
> +++ b/arch/s390/mm/maccess.c
> @@ -55,19 +55,22 @@ static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t siz
>   */
>  static DEFINE_SPINLOCK(s390_kernel_write_lock);
>  
> -void notrace s390_kernel_write(void *dst, const void *src, size_t size)
> +notrace void *s390_kernel_write(void *dst, const void *src, size_t size)
>  {
> +	void *tmp = dst;
>  	unsigned long flags;
>  	long copied;
>  
>  	spin_lock_irqsave(&s390_kernel_write_lock, flags);
>  	while (size) {
> -		copied = s390_kernel_write_odd(dst, src, size);
> -		dst += copied;
> +		copied = s390_kernel_write_odd(tmp, src, size);
> +		tmp += copied;
>  		src += copied;
>  		size -= copied;
>  	}
>  	spin_unlock_irqrestore(&s390_kernel_write_lock, flags);
> +
> +	return dst;
>  }
>  
>  static int __no_sanitize_address __memcpy_real(void *dest, void *src, size_t count)
> -- 
> 2.21.1
> 

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH v4 05/11] s390: Change s390_kernel_write() return type to match memcpy()

[Gerald Schaefer]

On Thu, 7 May 2020 15:36:48 +0200 (CEST)
Jiri Kosina <jikos@kernel.org> wrote:

> On Wed, 29 Apr 2020, Josh Poimboeuf wrote:
> 
> > s390_kernel_write()'s function type is almost identical to memcpy().
> > Change its return type to "void *" so they can be used interchangeably.
> > 
> > Cc: linux-s390@vger.kernel.org
> > Cc: heiko.carstens@de.ibm.com
> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
> > Acked-by: Miroslav Benes <mbenes@suse.cz>
> 
> Also for this one -- s390 folks, could you please provide your Ack for 
> taking things through livepatching.git as part of this series?
> 
> Thanks.
> 

Ah, forgot about that one, sorry. Also looks good.

Acked-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> # s390