[PATCH v2 1/3] s390: Always declare __mem functions

[PATCH v2 1/3] s390: Always declare __mem functions

[Marco Elver]

Like other architectures, always declare __mem*() functions if the
architecture defines __HAVE_ARCH_MEM*.

For example, this is required by sanitizer runtimes to unambiguously
refer to the arch versions of the mem-functions, and the compiler not
attempting any "optimizations" such as replacing the calls with builtins
(which may later be inlined etc.).

Signed-off-by: Marco Elver <elver@google.com>
---
v2:
* New patch.
---
 arch/s390/include/asm/string.h | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/s390/include/asm/string.h b/arch/s390/include/asm/string.h
index 3fae93ddb322..2c3c48d526b9 100644
--- a/arch/s390/include/asm/string.h
+++ b/arch/s390/include/asm/string.h
@@ -20,8 +20,11 @@
 #define __HAVE_ARCH_MEMSET64	/* arch function */
 
 void *memcpy(void *dest, const void *src, size_t n);
+void *__memcpy(void *dest, const void *src, size_t n);
 void *memset(void *s, int c, size_t n);
+void *__memset(void *s, int c, size_t n);
 void *memmove(void *dest, const void *src, size_t n);
+void *__memmove(void *dest, const void *src, size_t n);
 
 #ifndef CONFIG_KASAN
 #define __HAVE_ARCH_MEMCHR	/* inline & arch function */
@@ -55,10 +58,6 @@ char *strstr(const char *s1, const char *s2);
 
 #if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
 
-extern void *__memcpy(void *dest, const void *src, size_t n);
-extern void *__memset(void *s, int c, size_t n);
-extern void *__memmove(void *dest, const void *src, size_t n);
-
 /*
  * For files that are not instrumented (e.g. mm/slub.c) we
  * should use not instrumented version of mem* functions.
-- 
2.37.2.789.g6183377224-goog

[PATCH v2 2/3] kcsan: Instrument memcpy/memset/memmove with newer Clang

[Marco Elver]

With Clang version 16+, -fsanitize=thread will turn
memcpy/memset/memmove calls in instrumented functions into
__tsan_memcpy/__tsan_memset/__tsan_memmove calls respectively.

Add these functions to the core KCSAN runtime, so that we (a) catch data
races with mem* functions, and (b) won't run into linker errors with
such newer compilers.

Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Marco Elver <elver@google.com>
---
v2:
* Fix for architectures which do not provide their own
  memcpy/memset/memmove and instead use the generic versions in
  lib/string. In this case we'll just alias the __tsan_ variants.
---
 kernel/kcsan/core.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index fe12dfe254ec..4015f2a3e7f6 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -18,6 +18,7 @@
 #include <linux/percpu.h>
 #include <linux/preempt.h>
 #include <linux/sched.h>
+#include <linux/string.h>
 #include <linux/uaccess.h>
 
 #include "encoding.h"
@@ -1308,3 +1309,41 @@ noinline void __tsan_atomic_signal_fence(int memorder)
 	}
 }
 EXPORT_SYMBOL(__tsan_atomic_signal_fence);
+
+#ifdef __HAVE_ARCH_MEMSET
+void *__tsan_memset(void *s, int c, size_t count);
+noinline void *__tsan_memset(void *s, int c, size_t count)
+{
+	check_access(s, count, KCSAN_ACCESS_WRITE, _RET_IP_);
+	return __memset(s, c, count);
+}
+#else
+void *__tsan_memset(void *s, int c, size_t count) __alias(memset);
+#endif
+EXPORT_SYMBOL(__tsan_memset);
+
+#ifdef __HAVE_ARCH_MEMMOVE
+void *__tsan_memmove(void *dst, const void *src, size_t len);
+noinline void *__tsan_memmove(void *dst, const void *src, size_t len)
+{
+	check_access(dst, len, KCSAN_ACCESS_WRITE, _RET_IP_);
+	check_access(src, len, 0, _RET_IP_);
+	return __memmove(dst, src, len);
+}
+#else
+void *__tsan_memmove(void *dst, const void *src, size_t len) __alias(memmove);
+#endif
+EXPORT_SYMBOL(__tsan_memmove);
+
+#ifdef __HAVE_ARCH_MEMCPY
+void *__tsan_memcpy(void *dst, const void *src, size_t len);
+noinline void *__tsan_memcpy(void *dst, const void *src, size_t len)
+{
+	check_access(dst, len, KCSAN_ACCESS_WRITE, _RET_IP_);
+	check_access(src, len, 0, _RET_IP_);
+	return __memcpy(dst, src, len);
+}
+#else
+void *__tsan_memcpy(void *dst, const void *src, size_t len) __alias(memcpy);
+#endif
+EXPORT_SYMBOL(__tsan_memcpy);
-- 
2.37.2.789.g6183377224-goog

Re: [PATCH v2 2/3] kcsan: Instrument memcpy/memset/memmove with newer Clang

[Dmitry Vyukov]

On Fri, 9 Sept 2022 at 09:38, Marco Elver <elver@google.com> wrote:
>
> With Clang version 16+, -fsanitize=thread will turn
> memcpy/memset/memmove calls in instrumented functions into
> __tsan_memcpy/__tsan_memset/__tsan_memmove calls respectively.
>
> Add these functions to the core KCSAN runtime, so that we (a) catch data
> races with mem* functions, and (b) won't run into linker errors with
> such newer compilers.
>
> Cc: stable@vger.kernel.org # v5.10+
> Signed-off-by: Marco Elver <elver@google.com>
> ---
> v2:
> * Fix for architectures which do not provide their own
>   memcpy/memset/memmove and instead use the generic versions in
>   lib/string. In this case we'll just alias the __tsan_ variants.
> ---
>  kernel/kcsan/core.c | 39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
>
> diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
> index fe12dfe254ec..4015f2a3e7f6 100644
> --- a/kernel/kcsan/core.c
> +++ b/kernel/kcsan/core.c
> @@ -18,6 +18,7 @@
>  #include <linux/percpu.h>
>  #include <linux/preempt.h>
>  #include <linux/sched.h>
> +#include <linux/string.h>
>  #include <linux/uaccess.h>
>
>  #include "encoding.h"
> @@ -1308,3 +1309,41 @@ noinline void __tsan_atomic_signal_fence(int memorder)
>         }
>  }
>  EXPORT_SYMBOL(__tsan_atomic_signal_fence);
> +
> +#ifdef __HAVE_ARCH_MEMSET
> +void *__tsan_memset(void *s, int c, size_t count);
> +noinline void *__tsan_memset(void *s, int c, size_t count)
> +{
> +       check_access(s, count, KCSAN_ACCESS_WRITE, _RET_IP_);

These can use large sizes, does it make sense to truncate it to
MAX_ENCODABLE_SIZE?


> +       return __memset(s, c, count);
> +}
> +#else
> +void *__tsan_memset(void *s, int c, size_t count) __alias(memset);
> +#endif
> +EXPORT_SYMBOL(__tsan_memset);
> +
> +#ifdef __HAVE_ARCH_MEMMOVE
> +void *__tsan_memmove(void *dst, const void *src, size_t len);
> +noinline void *__tsan_memmove(void *dst, const void *src, size_t len)
> +{
> +       check_access(dst, len, KCSAN_ACCESS_WRITE, _RET_IP_);
> +       check_access(src, len, 0, _RET_IP_);
> +       return __memmove(dst, src, len);
> +}
> +#else
> +void *__tsan_memmove(void *dst, const void *src, size_t len) __alias(memmove);
> +#endif
> +EXPORT_SYMBOL(__tsan_memmove);
> +
> +#ifdef __HAVE_ARCH_MEMCPY
> +void *__tsan_memcpy(void *dst, const void *src, size_t len);
> +noinline void *__tsan_memcpy(void *dst, const void *src, size_t len)
> +{
> +       check_access(dst, len, KCSAN_ACCESS_WRITE, _RET_IP_);
> +       check_access(src, len, 0, _RET_IP_);
> +       return __memcpy(dst, src, len);
> +}
> +#else
> +void *__tsan_memcpy(void *dst, const void *src, size_t len) __alias(memcpy);
> +#endif
> +EXPORT_SYMBOL(__tsan_memcpy);
> --
> 2.37.2.789.g6183377224-goog
>

Re: [PATCH v2 2/3] kcsan: Instrument memcpy/memset/memmove with newer Clang

[Marco Elver]

On Fri, 9 Sept 2022 at 10:38, Dmitry Vyukov <dvyukov@google.com> wrote:
>
> On Fri, 9 Sept 2022 at 09:38, Marco Elver <elver@google.com> wrote:
> >
> > With Clang version 16+, -fsanitize=thread will turn
> > memcpy/memset/memmove calls in instrumented functions into
> > __tsan_memcpy/__tsan_memset/__tsan_memmove calls respectively.
> >
> > Add these functions to the core KCSAN runtime, so that we (a) catch data
> > races with mem* functions, and (b) won't run into linker errors with
> > such newer compilers.
> >
> > Cc: stable@vger.kernel.org # v5.10+
> > Signed-off-by: Marco Elver <elver@google.com>
> > ---
> > v2:
> > * Fix for architectures which do not provide their own
> >   memcpy/memset/memmove and instead use the generic versions in
> >   lib/string. In this case we'll just alias the __tsan_ variants.
> > ---
> >  kernel/kcsan/core.c | 39 +++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 39 insertions(+)
> >
> > diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
> > index fe12dfe254ec..4015f2a3e7f6 100644
> > --- a/kernel/kcsan/core.c
> > +++ b/kernel/kcsan/core.c
> > @@ -18,6 +18,7 @@
> >  #include <linux/percpu.h>
> >  #include <linux/preempt.h>
> >  #include <linux/sched.h>
> > +#include <linux/string.h>
> >  #include <linux/uaccess.h>
> >
> >  #include "encoding.h"
> > @@ -1308,3 +1309,41 @@ noinline void __tsan_atomic_signal_fence(int memorder)
> >         }
> >  }
> >  EXPORT_SYMBOL(__tsan_atomic_signal_fence);
> > +
> > +#ifdef __HAVE_ARCH_MEMSET
> > +void *__tsan_memset(void *s, int c, size_t count);
> > +noinline void *__tsan_memset(void *s, int c, size_t count)
> > +{
> > +       check_access(s, count, KCSAN_ACCESS_WRITE, _RET_IP_);
>
> These can use large sizes, does it make sense to truncate it to
> MAX_ENCODABLE_SIZE?

Hmm, good point - that way it can still set up watchpoints on them.
I'll do a v3.

[PATCH v2 3/3] objtool, kcsan: Add volatile read/write instrumentation to whitelist

[Marco Elver]

Adds KCSAN's volatile instrumentation to objtool's uaccess whitelist.

Recent kernel change have shown that this was missing from the uaccess
whitelist (since the first upstreamed version of KCSAN):

  mm/gup.o: warning: objtool: fault_in_readable+0x101: call to __tsan_volatile_write1() with UACCESS enabled

Fixes: 75d75b7a4d54 ("kcsan: Support distinguishing volatile accesses")
Signed-off-by: Marco Elver <elver@google.com>
---
v2:
* Fix commit message.
---
 tools/objtool/check.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index e55fdf952a3a..67afdce3421f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -999,6 +999,16 @@ static const char *uaccess_safe_builtin[] = {
 	"__tsan_read_write4",
 	"__tsan_read_write8",
 	"__tsan_read_write16",
+	"__tsan_volatile_read1",
+	"__tsan_volatile_read2",
+	"__tsan_volatile_read4",
+	"__tsan_volatile_read8",
+	"__tsan_volatile_read16",
+	"__tsan_volatile_write1",
+	"__tsan_volatile_write2",
+	"__tsan_volatile_write4",
+	"__tsan_volatile_write8",
+	"__tsan_volatile_write16",
 	"__tsan_atomic8_load",
 	"__tsan_atomic16_load",
 	"__tsan_atomic32_load",
-- 
2.37.2.789.g6183377224-goog

Re: [PATCH v2 3/3] objtool, kcsan: Add volatile read/write instrumentation to whitelist

[Dmitry Vyukov]

On Fri, 9 Sept 2022 at 09:38, Marco Elver <elver@google.com> wrote:
>
> Adds KCSAN's volatile instrumentation to objtool's uaccess whitelist.
>
> Recent kernel change have shown that this was missing from the uaccess
> whitelist (since the first upstreamed version of KCSAN):
>
>   mm/gup.o: warning: objtool: fault_in_readable+0x101: call to __tsan_volatile_write1() with UACCESS enabled
>
> Fixes: 75d75b7a4d54 ("kcsan: Support distinguishing volatile accesses")
> Signed-off-by: Marco Elver <elver@google.com>

Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

> ---
> v2:
> * Fix commit message.
> ---
>  tools/objtool/check.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index e55fdf952a3a..67afdce3421f 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -999,6 +999,16 @@ static const char *uaccess_safe_builtin[] = {
>         "__tsan_read_write4",
>         "__tsan_read_write8",
>         "__tsan_read_write16",
> +       "__tsan_volatile_read1",
> +       "__tsan_volatile_read2",
> +       "__tsan_volatile_read4",
> +       "__tsan_volatile_read8",
> +       "__tsan_volatile_read16",
> +       "__tsan_volatile_write1",
> +       "__tsan_volatile_write2",
> +       "__tsan_volatile_write4",
> +       "__tsan_volatile_write8",
> +       "__tsan_volatile_write16",
>         "__tsan_atomic8_load",
>         "__tsan_atomic16_load",
>         "__tsan_atomic32_load",
> --
> 2.37.2.789.g6183377224-goog
>

Re: [PATCH v2 1/3] s390: Always declare __mem functions

[Dmitry Vyukov]

On Fri, 9 Sept 2022 at 09:38, Marco Elver <elver@google.com> wrote:
>
> Like other architectures, always declare __mem*() functions if the
> architecture defines __HAVE_ARCH_MEM*.
>
> For example, this is required by sanitizer runtimes to unambiguously
> refer to the arch versions of the mem-functions, and the compiler not
> attempting any "optimizations" such as replacing the calls with builtins
> (which may later be inlined etc.).
>
> Signed-off-by: Marco Elver <elver@google.com>

Acked-by: Dmitry Vyukov <dvyukov@google.com>

> ---
> v2:
> * New patch.
> ---
>  arch/s390/include/asm/string.h | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/s390/include/asm/string.h b/arch/s390/include/asm/string.h
> index 3fae93ddb322..2c3c48d526b9 100644
> --- a/arch/s390/include/asm/string.h
> +++ b/arch/s390/include/asm/string.h
> @@ -20,8 +20,11 @@
>  #define __HAVE_ARCH_MEMSET64   /* arch function */
>
>  void *memcpy(void *dest, const void *src, size_t n);
> +void *__memcpy(void *dest, const void *src, size_t n);
>  void *memset(void *s, int c, size_t n);
> +void *__memset(void *s, int c, size_t n);
>  void *memmove(void *dest, const void *src, size_t n);
> +void *__memmove(void *dest, const void *src, size_t n);
>
>  #ifndef CONFIG_KASAN
>  #define __HAVE_ARCH_MEMCHR     /* inline & arch function */
> @@ -55,10 +58,6 @@ char *strstr(const char *s1, const char *s2);
>
>  #if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
>
> -extern void *__memcpy(void *dest, const void *src, size_t n);
> -extern void *__memset(void *s, int c, size_t n);
> -extern void *__memmove(void *dest, const void *src, size_t n);
> -
>  /*
>   * For files that are not instrumented (e.g. mm/slub.c) we
>   * should use not instrumented version of mem* functions.
> --
> 2.37.2.789.g6183377224-goog
>