Messages in this thread | | | Date | Fri, 5 Nov 2021 08:56:46 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH 11/22] x86,xen: Remove .fixup usage |
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On Thu, Nov 04, 2021 at 03:31:51PM -0700, Josh Poimboeuf wrote: > On Thu, Nov 04, 2021 at 05:47:40PM +0100, Peter Zijlstra wrote: > > Employ the fancy new EX_TYPE_IMM_REG to create EX_TYPE_NEG_REG to > > store '-1' into the designated register and use this to remove some > > Xen .fixup usage. > > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > --- > > arch/x86/include/asm/extable_fixup_types.h | 1 + > > arch/x86/include/asm/xen/page.h | 12 ++---------- > > 2 files changed, 3 insertions(+), 10 deletions(-) > > > > --- a/arch/x86/include/asm/extable_fixup_types.h > > +++ b/arch/x86/include/asm/extable_fixup_types.h > > @@ -35,5 +35,6 @@ > > > > #define EX_TYPE_IMM_REG 17 /* reg := (long)imm */ > > #define EX_TYPE_EFAULT_REG (EX_TYPE_IMM_REG | EX_TYPE_IMM(-EFAULT)) > > +#define EX_TYPE_NEG_REG (EX_TYPE_IMM_REG | EX_TYPE_IMM(-1)) > > > > #endif > > --- a/arch/x86/include/asm/xen/page.h > > +++ b/arch/x86/include/asm/xen/page.h > > @@ -96,11 +96,7 @@ static inline int xen_safe_write_ulong(u > > > > asm volatile("1: mov %[val], %[ptr]\n" > > "2:\n" > > - ".section .fixup, \"ax\"\n" > > - "3: sub $1, %[ret]\n" > > - " jmp 2b\n" > > - ".previous\n" > > - _ASM_EXTABLE(1b, 3b) > > + _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_NEG_REG, %[ret]) > > : [ret] "+r" (ret), [ptr] "=m" (*addr) > > : [val] "r" (val)); > > > > @@ -115,11 +111,7 @@ static inline int xen_safe_read_ulong(co > > > > asm volatile("1: mov %[ptr], %[rval]\n" > > "2:\n" > > - ".section .fixup, \"ax\"\n" > > - "3: sub $1, %[ret]\n" > > - " jmp 2b\n" > > - ".previous\n" > > - _ASM_EXTABLE(1b, 3b) > > + _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_NEG_REG, %[ret]) > > : [ret] "+r" (ret), [rval] "+r" (rval) > > : [ptr] "m" (*addr)); > > *val = rval; > > -EFAULT is also negative, and presumably more appropriate than -1.
Possibly, means I'll have to go audit all it's users. I'll put it on the todo list.
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