| Message ID | 20160913030846.29790-3-npiggin@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Tue, 2016-13-09 at 03:08:40 UTC, Nicholas Piggin wrote: > The syscall trampoline is not required, remove it. > > Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/a24553dd02dc6c7d2912af0b4b I rewrote the change log to be: powerpc/pseries: Remove unnecessary syscall trampoline When we originally added the ability to split the exception vectors from the kernel (commit 1f6a93e4c35e ("powerpc: Make it possible to move the interrupt handlers away from the kernel" 2008-09-15)), the LOAD_HANDLER() macro used an addi instruction to compute the offset of the common handler from the kernel base address. Using addi meant the handler had to be within 32K of the kernel base address, due to the addi instruction taking a signed immediate value. That necessitated creating a trampoline for the system call handler, because system_call_common (in entry64.S) is not linked within 32K of the kernel base address. Later in commit 61e2390ede3c ("powerpc: Make load_hander handle upto 64k offset" 2012-11-15) we changed LOAD_HANDLER to take a 64K offset, by changing it to use ori. Although system_call_common is not in head_64.S or exceptions-64s.S, it is included in head-y, which causes it to be linked early in the kernel text, so in practice it ends up below 64K. Additionally if it can't be placed below 64K the linker will fail to build with a "relocation truncated to fit" error. So remove the trampoline. Newer toolchains are able to work out that the ori in LOAD_HANDLER only takes a 16 bit offset, and so they generate a 16 bit relocation. Older toolchains (binutils 2.22 at least) are not so smart, so we have to add the @l annotation to tell the assembler to generate a 16 bit relocation. cheers
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 4015f71..ea57a2c 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -42,7 +42,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_REAL_LE) \ #define SYSCALL_PSERIES_2_RFID \ mfspr r12,SPRN_SRR1 ; \ ld r10,PACAKBASE(r13) ; \ - LOAD_HANDLER(r10, system_call_entry) ; \ + LOAD_HANDLER(r10, system_call_common) ; \ mtspr SPRN_SRR0,r10 ; \ ld r10,PACAKMSR(r13) ; \ mtspr SPRN_SRR1,r10 ; \ @@ -65,7 +65,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_REAL_LE) \ #define SYSCALL_PSERIES_2_DIRECT \ mflr r10 ; \ ld r12,PACAKBASE(r13) ; \ - LOAD_HANDLER(r12, system_call_entry) ; \ + LOAD_HANDLER(r12, system_call_common) ; \ mtctr r12 ; \ mfspr r12,SPRN_SRR1 ; \ /* Re-use of r13... No spare regs to do this */ \ @@ -910,10 +910,6 @@ hv_facility_unavailable_relon_trampoline: #endif STD_RELON_EXCEPTION_PSERIES(0x5700, 0x1700, altivec_assist) - .align 7 -system_call_entry: - b system_call_common - ppc64_runlatch_on_trampoline: b __ppc64_runlatch_on
The syscall trampoline is not required, remove it. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/kernel/exceptions-64s.S | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)