[RFC][PATCH 14/22] x86,ftrace: Remove .fixup usage

Peter Zijlstra
2021-11-04T16:57:09Z

Create and use EX_TYPE_ONE_REG to load 1 into the %[faulted] register
on exception.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/extable_fixup_types.h | 1 +
arch/x86/kernel/ftrace.c | 9 ++-------
2 files changed, 3 insertions(+), 7 deletions(-)

--- a/arch/x86/include/asm/extable_fixup_types.h
+++ b/arch/x86/include/asm/extable_fixup_types.h
@@ -37,5 +37,6 @@
#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))
#define EX_TYPE_ZERO_REG (EX_TYPE_IMM_REG | EX_TYPE_IMM(0))
+#define EX_TYPE_ONE_REG (EX_TYPE_IMM_REG | EX_TYPE_IMM(1))

#endif
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -661,13 +661,8 @@ void prepare_ftrace_return(unsigned long
" movl $0, %[faulted]\n"
"3:\n"

- ".section .fixup, \"ax\"\n"
- "4: movl $1, %[faulted]\n"
- " jmp 3b\n"
- ".previous\n"
-
- _ASM_EXTABLE(1b, 4b)
- _ASM_EXTABLE(2b, 4b)
+ _ASM_EXTABLE_TYPE_REG(1b, 3b, EX_TYPE_ONE_REG, %[faulted])
+ _ASM_EXTABLE_TYPE_REG(2b, 3b, EX_TYPE_ONE_REG, %[faulted])

: [old] "=&r" (old), [faulted] "=r" (faulted)
: [parent] "r" (parent), [return_hooker] "r" (return_hooker)