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tile: avoid undefined behavior with regs[TREG_TP] etc

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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>
This commit is contained in:
Chris Metcalf 2014-11-12 15:00:06 -05:00
parent a5c1cb63dd
commit ce433f8090
2 changed files with 20 additions and 10 deletions
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16
arch/tile/include/uapi/asm/ptrace.h
View File

@ -52,12 +52,16 @@ typedef uint_reg_t pt_reg_t;
* system call or exception. "struct sigcontext" has the same shape.
*/
struct pt_regs {
/* Saved main processor registers; 56..63 are special. */
/* tp, sp, and lr must immediately follow regs[] for aliasing. */
pt_reg_t regs[53];
pt_reg_t tp; /* aliases regs[TREG_TP] */
pt_reg_t sp; /* aliases regs[TREG_SP] */
pt_reg_t lr; /* aliases regs[TREG_LR] */
union {
/* Saved main processor registers; 56..63 are special. */
pt_reg_t regs[56];
struct {
pt_reg_t __regs[53];
pt_reg_t tp; /* aliases regs[TREG_TP] */
pt_reg_t sp; /* aliases regs[TREG_SP] */
pt_reg_t lr; /* aliases regs[TREG_LR] */
};
};
/* Saved special registers. */
pt_reg_t pc; /* stored in EX_CONTEXT_K_0 */

14
arch/tile/include/uapi/asm/sigcontext.h
View File

@ -24,10 +24,16 @@
* but is simplified since we know the fault is from userspace.
*/
struct sigcontext {
__uint_reg_t gregs[53]; /* General-purpose registers. */
__uint_reg_t tp; /* Aliases gregs[TREG_TP]. */
__uint_reg_t sp; /* Aliases gregs[TREG_SP]. */
__uint_reg_t lr; /* Aliases gregs[TREG_LR]. */
__extension__ union {
/* General-purpose registers. */
__uint_reg_t gregs[56];
__extension__ struct {
__uint_reg_t __gregs[53];
__uint_reg_t tp; /* Aliases gregs[TREG_TP]. */
__uint_reg_t sp; /* Aliases gregs[TREG_SP]. */
__uint_reg_t lr; /* Aliases gregs[TREG_LR]. */
};
};
__uint_reg_t pc; /* Program counter. */
__uint_reg_t ics; /* In Interrupt Critical Section? */
__uint_reg_t faultnum; /* Fault number. */