[glibc] powerpc: Add missing registers to clobbers list for syscalls [BZ #27623]

[glibc] powerpc: Add missing registers to clobbers list for syscalls [BZ #27623]

[Matheus Castanho]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=5d61fc2021922b4f572be218dad5b299e2939346

commit 5d61fc2021922b4f572be218dad5b299e2939346
Author: Matheus Castanho <msc@linux.ibm.com>
Date:   Wed Mar 17 10:14:15 2021 -0300

    powerpc: Add missing registers to clobbers list for syscalls [BZ #27623]
    
    Some registers that can be clobbered by the kernel during a syscall are not
    listed on the clobbers list in sysdeps/unix/sysv/linux/powerpc/sysdep.h.
    
    For syscalls using sc:
        - XER is zeroed by the kernel on exit
    
    For syscalls using scv:
        - XER is zeroed by the kernel on exit
        - Different from the sc case, most CR fields can be clobbered (according to
          the ELF ABI and the Linux kernel's syscall ABI for powerpc
          (linux/Documentation/powerpc/syscall64-abi.rst)
    
    The same should apply to vsyscalls, which effectively execute a function call
    but are not currently adding these registers as clobbers either.
    
    These are likely not causing issues today, but they should be added to the
    clobbers list just in case things change on the kernel side in the future.
    
    Reported-by: Nicholas Piggin <npiggin@gmail.com>
    Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
    Reviewed-by: Raphael M Zinsly <rzinsly@linux.ibm.com>

Diff:
---
 sysdeps/unix/sysv/linux/powerpc/sysdep.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/powerpc/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
index 6b99464e61..2f31f9177b 100644
--- a/sysdeps/unix/sysv/linux/powerpc/sysdep.h
+++ b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
@@ -56,7 +56,9 @@
        "0:"								\
        : "+r" (r0), "+r" (r3), "+r" (r4), "+r" (r5),  "+r" (r6),        \
          "+r" (r7), "+r" (r8)						\
-       : : "r9", "r10", "r11", "r12", "cr0", "ctr", "lr", "memory");	\
+       : : "r9", "r10", "r11", "r12",					\
+           "cr0", "cr1", "cr5", "cr6", "cr7",				\
+           "xer", "lr", "ctr", "memory");				\
     __asm__ __volatile__ ("" : "=r" (rval) : "r" (r3));		        \
     (long int) r0 & (1 << 28) ? -rval : rval;				\
   })
@@ -86,7 +88,8 @@
 	 "=&r" (r6), "=&r" (r7), "=&r" (r8)	\
        : ASM_INPUT_##nr			\
        : "r9", "r10", "r11", "r12",		\
-	 "lr", "ctr", "memory");		\
+	 "cr0", "cr1", "cr5", "cr6", "cr7",	\
+	 "xer", "lr", "ctr", "memory"); 	\
     r3;					\
   })
 
@@ -101,7 +104,7 @@
 	 "=&r" (r6), "=&r" (r7), "=&r" (r8)	\
        : ASM_INPUT_##nr			\
        : "r9", "r10", "r11", "r12",		\
-	 "cr0", "ctr", "memory");		\
+	 "xer", "cr0", "ctr", "memory");	\
     r0 & (1 << 28) ? -r3 : r3;			\
   })