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Date: Thu, 16 Apr 2020 08:16:35 -0500
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: Miroslav Benes <mbenes@...e.cz>
Cc: live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>,
Jessica Yu <jeyu@...nel.org>, linux-s390@...r.kernel.org,
heiko.carstens@...ibm.com
Subject: Re: [PATCH 4/7] s390/module: Use s390_kernel_write() for relocations
On Thu, Apr 16, 2020 at 07:06:51AM -0500, Josh Poimboeuf wrote:
> On Thu, Apr 16, 2020 at 10:56:02AM +0200, Miroslav Benes wrote:
> > > + bool early = me->state == MODULE_STATE_UNFORMED;
> > > +
> > > + return __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
> > > + early ? memcpy : s390_kernel_write);
> >
> > The compiler warns about
> >
> > arch/s390/kernel/module.c: In function 'apply_relocate_add':
> > arch/s390/kernel/module.c:453:24: warning: pointer type mismatch in conditional expression
> > early ? memcpy : s390_kernel_write);
>
> Thanks, I'll get all that cleaned up.
>
> I could have sworn I got a SUCCESS message from the kbuild bot. Does it
> ignore warnings nowadays?
Here's a fix on top of the original patch.
I changed s390_kernel_write() to return "void *" to match memcpy()
(probably a separate patch).
I also grabbed the text_mutex for the !early case in
apply_relocate_add() -- will do something similar for x86.
Will try to test this on a 390 box.
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/kernel/module.c b/arch/s390/kernel/module.c
index e85e378f876e..2b30ed0ce14f 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>
@@ -175,10 +176,11 @@ 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,
- void (*write)(void *dest, const void *src, size_t len))
+ 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;
@@ -196,28 +198,28 @@ static int apply_rela_bits(Elf_Addr loc, Elf_Addr val,
}
if (bits == 8) {
- write(loc, &val, 1);
+ write(dest, &val, 1);
} else if (bits == 12) {
unsigned short tmp = (val & 0xfff) |
(*(unsigned short *) loc & 0xf000);
- write(loc, &tmp, 2);
+ write(dest, &tmp, 2);
} else if (bits == 16) {
- write(loc, &val, 2);
+ write(dest, &val, 2);
} else if (bits == 20) {
unsigned int tmp = (val & 0xfff) << 16 |
(val & 0xff000) >> 4 | (*(unsigned int *) loc & 0xf00000ff);
- write(loc, &tmp, 4);
+ write(dest, &tmp, 4);
} else if (bits == 32) {
- write(loc, &val, 4);
+ write(dest, &val, 4);
} else if (bits == 64) {
- write(loc, &val, 8);
+ write(dest, &val, 8);
}
return 0;
}
static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
const char *strtab, struct module *me,
- void (*write)(void *dest, const void *src, size_t len))
+ void *(*write)(void *dest, const void *src, size_t len))
{
struct mod_arch_syminfo *info;
Elf_Addr loc, val;
@@ -419,7 +421,7 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
static int __apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
unsigned int symindex, unsigned int relsec,
struct module *me,
- void (*write)(void *dest, const void *src, size_t len))
+ void *(*write)(void *dest, const void *src, size_t len))
{
Elf_Addr base;
Elf_Sym *symtab;
@@ -435,7 +437,7 @@ static 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;
}
@@ -449,8 +451,16 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
int ret;
bool early = me->state == MODULE_STATE_UNFORMED;
- return __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
- early ? memcpy : s390_kernel_write);
+ if (!early)
+ mutex_lock(&text_mutex);
+
+ ret = __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
+ early ? memcpy : s390_kernel_write);
+
+ if (!early)
+ mutex_unlock(&text_mutex);
+
+ return ret;
}
int module_finalize(const Elf_Ehdr *hdr,
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)
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