The kernel compare and exchange calls will never succeed if they return -EFAULT. This change generates an instruction fault if a call returns -EFAULT. This prevents the code from spinning forever.
Tested on hppa-unknown-linux-gnu. Committed to trunk and gcc-11 branch.
Dave
---
Generate illegal instruction fault if LWS syscall returns -EFAULT.
2022-01-02 John David Anglin <dang...@gcc.gnu.org>
libgcc/ChangeLog:
* config/pa/linux-atomic.c (_ASM_EFAULT): Define.
(__kernel_cmpxchg): Nullify illegal iitlbp instruction if error
return is not equal _ASM_EFAULT.
(__kernel_cmpxchg2): Likewise.
diff --git a/libgcc/config/pa/linux-atomic.c b/libgcc/config/pa/linux-atomic.c
index 500a3652499..e4d74b2d598 100644
--- a/libgcc/config/pa/linux-atomic.c
+++ b/libgcc/config/pa/linux-atomic.c
@@ -28,6 +28,8 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If
not, see
#define EBUSY 16
#define ENOSYS 251
+#define _ASM_EFAULT "-14"
+
typedef unsigned char u8;
typedef short unsigned int u16;
#ifdef __LP64__
@@ -58,6 +60,8 @@ __kernel_cmpxchg (volatile void *mem, int oldval, int newval)
register long lws_errno asm("r21");
asm volatile ( "ble 0xb0(%%sr2, %%r0) \n\t"
"ldi %2, %%r20 \n\t"
+ "cmpiclr,<> " _ASM_EFAULT ", %%r21, %%r0\n\t"
+ "iitlbp %%r0,(%%sr0, %%r0) \n\t"
: "=r" (lws_ret), "=r" (lws_errno)
: "i" (LWS_CAS), "r" (lws_mem), "r" (lws_old), "r" (lws_new)
: "r1", "r20", "r22", "r23", "r29", "r31", "memory"
@@ -84,6 +88,8 @@ __kernel_cmpxchg2 (volatile void *mem, const void *oldval,
const void *newval,
register long lws_errno asm("r21");
asm volatile ( "ble 0xb0(%%sr2, %%r0) \n\t"
"ldi %6, %%r20 \n\t"
+ "cmpiclr,<> " _ASM_EFAULT ", %%r21, %%r0\n\t"
+ "iitlbp %%r0,(%%sr0, %%r0) \n\t"
: "=r" (lws_ret), "=r" (lws_errno), "+r" (lws_mem),
"+r" (lws_old), "+r" (lws_new), "+r" (lws_size)
: "i" (2)
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