| Message ID | 1417774619-30858-1-git-send-email-mpe@ellerman.id.au (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Michael Ellerman |
| Headers | show |
From: Michael Ellerman > Currently when we back trace something that is in a syscall we see > something like this: > > [c000000000000000] [c000000000000000] SyS_read+0x6c/0x110 > [c000000000000000] [c000000000000000] syscall_exit+0x0/0x98 > > Although it's entirely correct, seeing syscall_exit at the bottom can be > confusing - we were exiting from a syscall and then called SyS_read() ? > > If we instead change syscall_exit to be a local label we get something > more intuitive: > > [c0000001fa46fde0] [c00000000026719c] SyS_read+0x6c/0x110 > [c0000001fa46fe30] [c000000000009264] system_call+0x38/0xd0 > > ie. we were handling a system call, and it was SyS_read(). > > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> > --- > arch/powerpc/kernel/entry_64.S | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S > index 0905c8da90f1..d8828e50dbef 100644 > --- a/arch/powerpc/kernel/entry_64.S > +++ b/arch/powerpc/kernel/entry_64.S > @@ -178,7 +178,7 @@ system_call: /* label this so stack traces look sane */ > mtctr r12 > bctrl /* Call handler */ Why not add a 'nop' here instead? > -syscall_exit: > +.Lsyscall_exit: > std r3,RESULT(r1) > #ifdef SHOW_SYSCALLS > bl do_show_syscall_exit > @@ -270,7 +270,7 @@ syscall_dotrace: ... David
On Fri, 2014-12-05 at 10:27 +0000, David Laight wrote: > From: Michael Ellerman > > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S > > index 0905c8da90f1..d8828e50dbef 100644 > > --- a/arch/powerpc/kernel/entry_64.S > > +++ b/arch/powerpc/kernel/entry_64.S > > @@ -178,7 +178,7 @@ system_call: /* label this so stack traces look sane */ > > mtctr r12 > > bctrl /* Call handler */ > > Why not add a 'nop' here instead? Because we'd rather not add extra instructions to the syscall path unless we really need to. A local label seems like the preferable solution to me. cheers
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 0905c8da90f1..d8828e50dbef 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -178,7 +178,7 @@ system_call: /* label this so stack traces look sane */ mtctr r12 bctrl /* Call handler */ -syscall_exit: +.Lsyscall_exit: std r3,RESULT(r1) #ifdef SHOW_SYSCALLS bl do_show_syscall_exit @@ -270,7 +270,7 @@ syscall_dotrace: syscall_enosys: li r3,-ENOSYS - b syscall_exit + b .Lsyscall_exit syscall_exit_work: #ifdef CONFIG_PPC_BOOK3S @@ -347,33 +347,33 @@ _GLOBAL(save_nvgprs) _GLOBAL(ppc_fork) bl save_nvgprs bl sys_fork - b syscall_exit + b .Lsyscall_exit _GLOBAL(ppc_vfork) bl save_nvgprs bl sys_vfork - b syscall_exit + b .Lsyscall_exit _GLOBAL(ppc_clone) bl save_nvgprs bl sys_clone - b syscall_exit + b .Lsyscall_exit _GLOBAL(ppc32_swapcontext) bl save_nvgprs bl compat_sys_swapcontext - b syscall_exit + b .Lsyscall_exit _GLOBAL(ppc64_swapcontext) bl save_nvgprs bl sys_swapcontext - b syscall_exit + b .Lsyscall_exit _GLOBAL(ret_from_fork) bl schedule_tail REST_NVGPRS(r1) li r3,0 - b syscall_exit + b .Lsyscall_exit _GLOBAL(ret_from_kernel_thread) bl schedule_tail @@ -385,7 +385,7 @@ _GLOBAL(ret_from_kernel_thread) #endif blrl li r3,0 - b syscall_exit + b .Lsyscall_exit /* * This routine switches between two different tasks. The process
Currently when we back trace something that is in a syscall we see something like this: [c000000000000000] [c000000000000000] SyS_read+0x6c/0x110 [c000000000000000] [c000000000000000] syscall_exit+0x0/0x98 Although it's entirely correct, seeing syscall_exit at the bottom can be confusing - we were exiting from a syscall and then called SyS_read() ? If we instead change syscall_exit to be a local label we get something more intuitive: [c0000001fa46fde0] [c00000000026719c] SyS_read+0x6c/0x110 [c0000001fa46fe30] [c000000000009264] system_call+0x38/0xd0 ie. we were handling a system call, and it was SyS_read(). Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> --- arch/powerpc/kernel/entry_64.S | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)