ARC: [Review] Preparing to fix incorrect syscall restarts due to signals
To avoid multiple syscall restarts (multiple signals) or no restart at
all (sigreturn), we need just an extra bit of state "literally 1 bit" in
struct pt_regs. orig_r8 is the best place to do this, however given the
way it is encoded currently, we can't add anything simplistically.
Current orig_r8:
* syscalls -> 1 to NR_SYSCALLS
* Exceptions -> NR_SYSCALLS + 1
* Break-point-> NR_SYSCALLS + 2
In new scheme it is a bit-field
* lower short word contains the exact event type (and a new bit to represent
restart semantics : if syscall was already / can't be restarted)
* upper short word optionally containing the syscall num - needed by
likes of tracehooks etc
This patch only changes how orig_r8 is organised and nothing should
change behaviourily.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
diff --git a/arch/arc/include/asm/entry.h b/arch/arc/include/asm/entry.h
index 6b42bf5..9eada5b 100644
--- a/arch/arc/include/asm/entry.h
+++ b/arch/arc/include/asm/entry.h
@@ -343,18 +343,12 @@
*-------------------------------------------------------------*/
.macro SAVE_ALL_EXCEPTION marker
+ st \marker, [sp, 8]
+ st r0, [sp, 4] /* orig_r0, needed only for sys calls */
+
/* Restore r9 used to code the early prologue */
EXCPN_PROLOG_RESTORE_REG r9
- /* Save the complete regfile now */
-
- /* orig_r8 marker:
- * syscalls -> 1 to NR_SYSCALLS
- * Exceptions -> NR_SYSCALLS + 1
- * Break-point-> NR_SYSCALLS + 2
- */
- st \marker, [sp, 8]
- st r0, [sp, 4] /* orig_r0, needed only for sys calls */
SAVE_CALLER_SAVED
st.a r26, [sp, -4] /* gp */
st.a fp, [sp, -4]
@@ -384,14 +378,25 @@
* Save scratch regs for exceptions
*-------------------------------------------------------------*/
.macro SAVE_ALL_SYS
- SAVE_ALL_EXCEPTION (NR_syscalls + 1)
+ SAVE_ALL_EXCEPTION orig_r8_IS_EXCPN
.endm
/*--------------------------------------------------------------
* Save scratch regs for sys calls
*-------------------------------------------------------------*/
.macro SAVE_ALL_TRAP
- SAVE_ALL_EXCEPTION r8
+ /*
+ * Setup pt_regs->orig_r8.
+ * Encode syscall number (r8) in upper short word of event type (r9)
+ * N.B. #1: This is already endian safe (see ptrace.h)
+ * #2: Only r9 can be used as scratch as it is already clobbered
+ * and it's contents are no longer needed by the latter part
+ * of exception prologue
+ */
+ lsl r9, r8, 16
+ or r9, r9, orig_r8_IS_SCALL
+
+ SAVE_ALL_EXCEPTION r9
.endm
/*--------------------------------------------------------------
@@ -442,7 +447,7 @@
ld r9, [@int1_saved_reg]
/* now we are ready to save the remaining context :) */
- st -1, [sp, 8] /* orig_r8, -1 for interuppt level one */
+ st orig_r8_IS_IRQ1, [sp, 8] /* Event Type */
st 0, [sp, 4] /* orig_r0 , N/A for IRQ */
SAVE_CALLER_SAVED
st.a r26, [sp, -4] /* gp */