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powerpc: Relocatable system call no longer uses the LR 

We had some code to restore the LR in the relocatable system call path
back when we used the LR to do an indirect branch.

Commit 6a404806df ("powerpc: Avoid link stack corruption in MMU
on syscall entry path") changed this to use the CTR which is volatile
across system calls so does not need restoring.

Remove the stale comment and the restore of the LR.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Anton Blanchard 2015-05-26 15:46:54 +10:00 committed by Michael Ellerman
parent 72e349f112
commit 05b05f28fb
1 changed files with 4 additions and 12 deletions
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16
arch/powerpc/kernel/exceptions-64s.S
View File

@ -59,14 +59,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_REAL_LE) \
#if defined(CONFIG_RELOCATABLE)
/*
* We can't branch directly; in the direct case we use LR
* and system_call_entry restores LR. (We thus need to move
* LR to r10 in the RFID case too.)
* We can't branch directly so we do it via the CTR which
* is volatile across system calls.
*/
#define SYSCALL_PSERIES_2_DIRECT \
mflr r10 ; \
ld r12,PACAKBASE(r13) ; \
LOAD_HANDLER(r12, system_call_entry_direct) ; \
LOAD_HANDLER(r12, system_call_entry) ; \
mtctr r12 ; \
mfspr r12,SPRN_SRR1 ; \
/* Re-use of r13... No spare regs to do this */ \
@ -80,7 +79,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_REAL_LE) \
mfspr r12,SPRN_SRR1 ; \
li r10,MSR_RI ; \
mtmsrd r10,1 ; /* Set RI (EE=0) */ \
b system_call_entry_direct ;
b system_call_entry ;
#endif
/*
@ -969,13 +968,6 @@ hv_facility_unavailable_relon_trampoline:
__end_interrupts:
.align 7
system_call_entry_direct:
#if defined(CONFIG_RELOCATABLE)
/* The first level prologue may have used LR to get here, saving
* orig in r10. To save hacking/ifdeffing common code, restore here.
*/
mtlr r10
#endif
system_call_entry:
b system_call_common