[PATCH] powerpc/syscalls/trace: Fix mmap in syscalls_trace

[PATCH] powerpc/syscalls/trace: Fix mmap in syscalls_trace

[Balbir Singh]

This patch uses SYSCALL_DEFINE6 for sys_mmap and sys_mmap2
so that the meta-data associated with these syscalls is
visible to the syscall tracer. In the absence of this
generic syscalls (defined outside arch) like munmap,etc.
are visible in available_events, syscall_enter_mmap and
syscall_exit_mmap is not.

A side-effect of this change is that the return type has
changed from unsigned long to long.

Prior to these changes, we had, under /sys/kernel/tracing

cat available_events  | grep syscalls | grep map
syscalls:sys_exit_remap_file_pages
syscalls:sys_enter_remap_file_pages
syscalls:sys_exit_munmap
syscalls:sys_enter_munmap
syscalls:sys_exit_mremap
syscalls:sys_enter_mremap

After these changes we have mmap in available_events.

cat available_events  | grep syscalls | grep map
syscalls:sys_exit_mmap
syscalls:sys_enter_mmap
syscalls:sys_exit_remap_file_pages
syscalls:sys_enter_remap_file_pages
syscalls:sys_exit_munmap
syscalls:sys_enter_munmap
syscalls:sys_exit_mremap
syscalls:sys_enter_mremap

Sample trace:
     cat-3399  [001] ....   196.542410: sys_mmap(addr: 7fff922a0000, len: 20000, prot: 3, flags: 812, fd: 3, offset: 1b0000)
     cat-3399  [001] ....   196.542443: sys_mmap -> 0x7fff922a0000
     cat-3399  [001] ....   196.542668: sys_munmap(addr: 7fff922c0000, len: 6d2c)
     cat-3399  [001] ....   196.542677: sys_munmap -> 0x0

Signed-off-by: Balbir Singh <bsingharora@gmail.com>
---

 Changelog:
   Removed RFC
   Fixed len from unsigned long to size_t
   Added some examples of use of mmap trace

 arch/powerpc/include/asm/syscalls.h |  4 ++--
 arch/powerpc/kernel/syscalls.c      | 16 ++++++++--------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 23be8f1..16fab68 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -8,10 +8,10 @@
 
 struct rtas_args;
 
-asmlinkage unsigned long sys_mmap(unsigned long addr, size_t len,
+asmlinkage long sys_mmap(unsigned long addr, size_t len,
 		unsigned long prot, unsigned long flags,
 		unsigned long fd, off_t offset);
-asmlinkage unsigned long sys_mmap2(unsigned long addr, size_t len,
+asmlinkage long sys_mmap2(unsigned long addr, size_t len,
 		unsigned long prot, unsigned long flags,
 		unsigned long fd, unsigned long pgoff);
 asmlinkage long ppc64_personality(unsigned long personality);
diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index de04c9f..a877bf8 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -42,11 +42,11 @@
 #include <asm/unistd.h>
 #include <asm/asm-prototypes.h>
 
-static inline unsigned long do_mmap2(unsigned long addr, size_t len,
+static inline long do_mmap2(unsigned long addr, size_t len,
 			unsigned long prot, unsigned long flags,
 			unsigned long fd, unsigned long off, int shift)
 {
-	unsigned long ret = -EINVAL;
+	long ret = -EINVAL;
 
 	if (!arch_validate_prot(prot))
 		goto out;
@@ -62,16 +62,16 @@ static inline unsigned long do_mmap2(unsigned long addr, size_t len,
 	return ret;
 }
 
-unsigned long sys_mmap2(unsigned long addr, size_t len,
-			unsigned long prot, unsigned long flags,
-			unsigned long fd, unsigned long pgoff)
+SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
+		unsigned long, prot, unsigned long, flags,
+		unsigned long, fd, unsigned long, pgoff)
 {
 	return do_mmap2(addr, len, prot, flags, fd, pgoff, PAGE_SHIFT-12);
 }
 
-unsigned long sys_mmap(unsigned long addr, size_t len,
-		       unsigned long prot, unsigned long flags,
-		       unsigned long fd, off_t offset)
+SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
+		unsigned long, prot, unsigned long, flags,
+		unsigned long, fd, off_t, offset)
 {
 	return do_mmap2(addr, len, prot, flags, fd, offset, PAGE_SHIFT);
 }
-- 
2.9.3

Re: powerpc/syscalls/trace: Fix mmap in syscalls_trace

[Michael Ellerman]

On Wed, 2017-04-12 at 06:35:19 UTC, Balbir Singh wrote:
> This patch uses SYSCALL_DEFINE6 for sys_mmap and sys_mmap2
> so that the meta-data associated with these syscalls is
> visible to the syscall tracer. In the absence of this
> generic syscalls (defined outside arch) like munmap,etc.
> are visible in available_events, syscall_enter_mmap and
> syscall_exit_mmap is not.
> 
> A side-effect of this change is that the return type has
> changed from unsigned long to long.
...
> 
> Signed-off-by: Balbir Singh <bsingharora@gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/9c355917fcf006af47ffaa5ae43a1a

cheers