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kernel
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linux
tile: avoid undefined behavior with regs[TREG_TP] etc
Recent compilers warn about accesses to arrays past the end,
which is supported for pt_regs and sigcontext with the
intended alias past the end of regs[] to sp, tp, and lr
using TREG_SP, TREG_TP, and TREG_LR.
Make the intended usage explict by providing an anonymous
union of regs[56] on the one hand, and a short __regs[53]
on the other followed by the sp, tp, and lr fields, so the
aliasing is done explicitly and is visible to the compiler.
Reviewed-by: Jeff Epler <jepler@unpythonic.net>
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
+20
-10
+10
-6
arch/tile/include/uapi/asm/ptrace.h
+10
-6
arch/tile/include/uapi/asm/ptrace.h
···
52
52
* system call or exception. "struct sigcontext" has the same shape.
53
53
*/
54
54
struct pt_regs {
55
-
/* Saved main processor registers; 56..63 are special. */
56
-
/* tp, sp, and lr must immediately follow regs[] for aliasing. */
57
-
pt_reg_t regs[53];
58
-
pt_reg_t tp; /* aliases regs[TREG_TP] */
59
-
pt_reg_t sp; /* aliases regs[TREG_SP] */
60
-
pt_reg_t lr; /* aliases regs[TREG_LR] */
55
+
union {
56
+
/* Saved main processor registers; 56..63 are special. */
57
+
pt_reg_t regs[56];
58
+
struct {
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+
pt_reg_t __regs[53];
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+
pt_reg_t tp; /* aliases regs[TREG_TP] */
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+
pt_reg_t sp; /* aliases regs[TREG_SP] */
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+
pt_reg_t lr; /* aliases regs[TREG_LR] */
63
+
};
64
+
};
61
65
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/* Saved special registers. */
63
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pt_reg_t pc; /* stored in EX_CONTEXT_K_0 */
+10
-4
arch/tile/include/uapi/asm/sigcontext.h
+10
-4
arch/tile/include/uapi/asm/sigcontext.h
···
24
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* but is simplified since we know the fault is from userspace.
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*/
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struct sigcontext {
27
-
__uint_reg_t gregs[53]; /* General-purpose registers. */
28
-
__uint_reg_t tp; /* Aliases gregs[TREG_TP]. */
29
-
__uint_reg_t sp; /* Aliases gregs[TREG_SP]. */
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-
__uint_reg_t lr; /* Aliases gregs[TREG_LR]. */
27
+
__extension__ union {
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+
/* General-purpose registers. */
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+
__uint_reg_t gregs[56];
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+
__extension__ struct {
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+
__uint_reg_t __gregs[53];
32
+
__uint_reg_t tp; /* Aliases gregs[TREG_TP]. */
33
+
__uint_reg_t sp; /* Aliases gregs[TREG_SP]. */
34
+
__uint_reg_t lr; /* Aliases gregs[TREG_LR]. */
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+
};
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+
};
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__uint_reg_t pc; /* Program counter. */
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__uint_reg_t ics; /* In Interrupt Critical Section? */
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__uint_reg_t faultnum; /* Fault number. */