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x86/extable: switch to using FIELD_GET_SIGNED()

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The EX_DATA register is laid out such that EX_DATA_IMM occupied MSB.
It's done to make sure that FIELD_GET() will sign-extend the IMM
field during extraction.

To enforce that, all EX_DATA masks are made signed integers. This
works, but relies on the particular implementation of FIELD_GET(),
i.e. masking then shifting, not vice versa; and the particular
placement of the fields in the register.

Switch to using the dedicated FIELD_GET_SIGNED(), and relax those
limitations.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Yury Norov <ynorov@nvidia.com>
This commit is contained in:
Yury Norov
2026-04-27 17:41:19 -04:00
parent 2c3f0541b9
commit d3d4233c7c
2 changed files with 5 additions and 10 deletions
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13
arch/x86/include/asm/extable_fixup_types.h
View File

@@ -2,15 +2,10 @@
#ifndef _ASM_X86_EXTABLE_FIXUP_TYPES_H
#define _ASM_X86_EXTABLE_FIXUP_TYPES_H
/*
* Our IMM is signed, as such it must live at the top end of the word. Also,
* since C99 hex constants are of ambiguous type, force cast the mask to 'int'
* so that FIELD_GET() will DTRT and sign extend the value when it extracts it.
*/
#define EX_DATA_TYPE_MASK ((int)0x000000FF)
#define EX_DATA_REG_MASK ((int)0x00000F00)
#define EX_DATA_FLAG_MASK ((int)0x0000F000)
#define EX_DATA_IMM_MASK ((int)0xFFFF0000)
#define EX_DATA_TYPE_MASK (0x000000FF)
#define EX_DATA_REG_MASK (0x00000F00)
#define EX_DATA_FLAG_MASK (0x0000F000)
#define EX_DATA_IMM_MASK (0xFFFF0000)
#define EX_DATA_REG_SHIFT 8
#define EX_DATA_FLAG_SHIFT 12

2
arch/x86/mm/extable.c
View File

@@ -322,7 +322,7 @@ int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,
type = FIELD_GET(EX_DATA_TYPE_MASK, e->data);
reg = FIELD_GET(EX_DATA_REG_MASK, e->data);
imm = FIELD_GET(EX_DATA_IMM_MASK, e->data);
imm = FIELD_GET_SIGNED(EX_DATA_IMM_MASK, e->data);
switch (type) {
case EX_TYPE_DEFAULT: