| Message ID | 20180801185331.39535-1-ndesaulniers@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] sh: prefer _THIS_IP_ to current_text_addr | expand |
On Wed, 1 Aug 2018 11:53:31 -0700 Nick Desaulniers <ndesaulniers@google.com> wrote: > As part of the effort to reduce the code duplication between _THIS_IP_ > and current_text_addr(), let's consolidate callers of > current_text_addr() to use _THIS_IP_. Why not switch everything to current_text_addr()? _THIS_IP_ is ugly ;) Several architectures (s390, sparc, sh, ...) do funky things in their current_text_addr(). Does the generic kernel.h implementation of current_text_addr() work OK on those architectures? -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Aug 1, 2018 at 2:55 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Wed, 1 Aug 2018 11:53:31 -0700 Nick Desaulniers <ndesaulniers@google.com> wrote: > > > As part of the effort to reduce the code duplication between _THIS_IP_ > > and current_text_addr(), let's consolidate callers of > > current_text_addr() to use _THIS_IP_. > > Why not switch everything to current_text_addr()? _THIS_IP_ is ugly ;) > > Several architectures (s390, sparc, sh, ...) do funky things in their > current_text_addr(). Does the generic kernel.h implementation of > current_text_addr() work OK on those architectures? Good question, one I've been mulling over for a few days. That's definitely something that I've considered. Mostly, it comes down to there being fewer call sites of current_text_addr() than _THIS_IP_, so it's IMO a smaller change that doesn't require coordinating tree-wide changes. What's interesting about current_text_addr() is that while there are many arch specific definitions, there are only 5 call sites in the whole kernel (and 4 of them are arch specific). So unless there's an arch specific reason to prefer inline assembly over higher level C (yes, returning the address of a label in a statement expression is ugly), (it looks like parisc might have a reason, at its lone call site, see: https://lkml.org/lkml/2018/8/1/1678, TBD), then I don't think that current_text_addr() has a raison d'être. I suspect that its use predates the GNU C extensions needed for the current generic C implementation (statement expressions + addr of label) and has just been reimplemented in every new arch's arch/*/include/asm/processor.h simply because the other archs had it. So the plan is to replace the 5 call sites of current_text_addr() with _THIS_IP_ (if possible), then delete all definitions of the arch specific current_text_addr()'s. This can be done on a per tree basis, rather than a treewide patch for converting _THIS_IP_ (who has many more call sites) to current_text_addr(). What do you think?
On Wed, 1 Aug 2018 15:06:33 -0700 Nick Desaulniers <ndesaulniers@google.com> wrote: > So the plan is to replace the 5 call sites of current_text_addr() with > _THIS_IP_ (if possible), then delete all definitions of the arch > specific current_text_addr()'s. This can be done on a per tree basis, > rather than a treewide patch for converting _THIS_IP_ (who has many > more call sites) to current_text_addr(). What do you think? Sounds good to me. -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/sh/include/asm/kexec.h b/arch/sh/include/asm/kexec.h index fd5f331a3912..927d80ba2332 100644 --- a/arch/sh/include/asm/kexec.h +++ b/arch/sh/include/asm/kexec.h @@ -4,6 +4,7 @@ #include <asm/ptrace.h> #include <asm/string.h> +#include <linux/kernel.h> /* * KEXEC_SOURCE_MEMORY_LIMIT maximum page get_free_page can return. @@ -61,7 +62,7 @@ static inline void crash_setup_regs(struct pt_regs *newregs, __asm__ __volatile__ ("stc gbr, %0" : "=r" (newregs->gbr)); __asm__ __volatile__ ("stc sr, %0" : "=r" (newregs->sr)); - newregs->pc = (unsigned long)current_text_addr(); + newregs->pc = _THIS_IP_; } } #else diff --git a/arch/sh/kernel/dwarf.c b/arch/sh/kernel/dwarf.c index 1a2526676a87..bb511e2d9d68 100644 --- a/arch/sh/kernel/dwarf.c +++ b/arch/sh/kernel/dwarf.c @@ -599,7 +599,7 @@ struct dwarf_frame *dwarf_unwind_stack(unsigned long pc, * time this function makes its first function call. */ if (!pc || !prev) - pc = (unsigned long)current_text_addr(); + pc = _THIS_IP_; #ifdef CONFIG_FUNCTION_GRAPH_TRACER /*
As part of the effort to reduce the code duplication between _THIS_IP_ and current_text_addr(), let's consolidate callers of current_text_addr() to use _THIS_IP_. Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> --- arch/sh/include/asm/kexec.h | 3 ++- arch/sh/kernel/dwarf.c | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-)