Messages in this thread | | | Date | Fri, 24 Jul 2015 10:56:18 +0100 | From | Mark Rutland <> | Subject | Re: [RFC] arm64:use set_fixmap_offset to make it more clear |
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On Fri, Jul 24, 2015 at 04:56:59AM +0100, yalin wang wrote: > > > On Jul 23, 2015, at 21:03, Catalin Marinas <catalin.marinas@arm.com> wrote: > > > > On Thu, Jul 23, 2015 at 07:45:53PM +0800, yalin wang wrote: > >> A little change to patch_map() function, > >> use set_fixmap_offset() to make code more clear. > >> > >> Signed-off-by: yalin wang <yalin.wang2010@gmail.com> > >> --- > >> arch/arm64/kernel/insn.c | 5 ++--- > >> 1 file changed, 2 insertions(+), 3 deletions(-) > >> > >> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c > >> index dd9671c..7dafd5a 100644 > >> --- a/arch/arm64/kernel/insn.c > >> +++ b/arch/arm64/kernel/insn.c > >> @@ -101,9 +101,8 @@ static void __kprobes *patch_map(void *addr, int fixmap) > >> return addr; > >> > >> BUG_ON(!page); > >> - set_fixmap(fixmap, page_to_phys(page)); > >> - > >> - return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK)); > >> + return (void *)set_fixmap_offset(fixmap, page_to_phys(page) + > >> + (addr & ~PAGE_MASK)); > > > > It looks fine. Do you get any compiler warning for the automatic pointer > > to long conversion? You may want to add some explicit casts, otherwise: > > > > Acked-by: Catalin Marinas <catalin.marinas@arm.com> > i have build it, there is no warning about this change. :)
I see no warnings with defconfig, but there's an (unrelated) set of warnings if CONFIG_DEBUG_SET_MODULE_RONX or CONFIG_DEBUG_RODATA are enabled:
---- In file included from ./arch/arm64/include/asm/fixmap.h:85:0, from arch/arm64/kernel/insn.c:32: arch/arm64/kernel/insn.c: In function ‘__aarch64_insn_write’: include/asm-generic/fixmap.h:73:2: warning: ‘addr’ may be used uninitialized in this function [-Wmaybe-uninitialized] __set_fixmap(idx, phys, flags); \ ^ include/asm-generic/fixmap.h:72:16: note: ‘addr’ was declared here unsigned long addr; \ ^ include/asm-generic/fixmap.h:79:2: note: in expansion of macro ‘__set_fixmap_offset’ __set_fixmap_offset(idx, phys, FIXMAP_PAGE_NORMAL) ^ arch/arm64/kernel/insn.c:104:17: note: in expansion of macro ‘set_fixmap_offset’ return (void *)set_fixmap_offset(fixmap, page_to_phys(page) + ^ ----
That seems to be due to the definition of __set_fixmap_offset in asm-generic/fixmap.h:
/* Return a pointer with offset calculated */ #define __set_fixmap_offset(idx, phys, flags) \ ({ \ unsigned long addr; \ __set_fixmap(idx, phys, flags); \ addr = fix_to_virt(idx) + ((phys) & (PAGE_SIZE - 1)); \ addr; \ })
Where that new addr variable shadows patch_map's addr argument when the call to __set_fixmap is expanded.
Which means that this patch currently breaks CONFIG_DEBUG_SET_MODULE_RONX and CONFIG_DEBUG_RODATA.
Thanks, Mark.
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