Messages in this thread | | | Date | Thu, 4 Nov 2021 15:31:51 -0700 | From | Josh Poimboeuf <> | Subject | Re: [RFC][PATCH 11/22] x86,xen: Remove .fixup usage |
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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.
Could we just use EX_TYPE_EFAULT_REG?
-- Josh
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