[RFC][PATCH 11/22] x86,xen: Remove .fixup usage

Peter Zijlstra
2021-11-04T16:56:59Z

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;