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>
diff --git a/arch/tile/include/uapi/asm/ptrace.h b/arch/tile/include/uapi/asm/ptrace.h
index 7757e19..d03b829 100644
--- a/arch/tile/include/uapi/asm/ptrace.h
+++ b/arch/tile/include/uapi/asm/ptrace.h
@@ -52,12 +52,16 @@
* 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 */
diff --git a/arch/tile/include/uapi/asm/sigcontext.h b/arch/tile/include/uapi/asm/sigcontext.h
index 6348e59..39ff5d1a 100644
--- a/arch/tile/include/uapi/asm/sigcontext.h
+++ b/arch/tile/include/uapi/asm/sigcontext.h
@@ -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. */