Re: [RFC PATCH 1/6] powerpc/64s: Fix assembly to support larger values of THREAD_SIZE

When CONFIG_VMAP_STACK is enabled, we set THREAD_SIZE to be at least the
size of a page.

There's a few bits of assembly in the book3s64 code that use THREAD_SIZE in
immediate mode instructions, which can only take an operand of up to 16
bits signed, which isn't quite large enough.

Fix these spots to use a scratch register or use two immediate mode
instructions instead, so we can later enable VMAP_STACK.

Signed-off-by: Andrew Donnellan <redacted>
---
  arch/powerpc/include/asm/asm-compat.h   | 2 ++
  arch/powerpc/kernel/entry_64.S          | 4 +++-
  arch/powerpc/kernel/irq.c               | 8 ++++++--
  arch/powerpc/kernel/misc_64.S           | 4 +++-
  arch/powerpc/kvm/book3s_hv_rmhandlers.S | 3 ++-
  5 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/asm-compat.h b/arch/powerpc/include/asm/asm-compat.h
index 2bc53c646ccd..30dd7813bf3b 100644
--- a/arch/powerpc/include/asm/asm-compat.h
+++ b/arch/powerpc/include/asm/asm-compat.h

@@ -11,6 +11,7 @@
  #define PPC_LL		stringify_in_c(ld)
  #define PPC_STL		stringify_in_c(std)
  #define PPC_STLU	stringify_in_c(stdu)
+#define PPC_STLUX	stringify_in_c(stdux)
  #define PPC_LCMPI	stringify_in_c(cmpdi)
  #define PPC_LCMPLI	stringify_in_c(cmpldi)
  #define PPC_LCMP	stringify_in_c(cmpd)

@@ -45,6 +46,7 @@
  #define PPC_LL		stringify_in_c(lwz)
  #define PPC_STL		stringify_in_c(stw)
  #define PPC_STLU	stringify_in_c(stwu)
+#define PPC_STLUX	stringify_in_c(stwux)
  #define PPC_LCMPI	stringify_in_c(cmpwi)
  #define PPC_LCMPLI	stringify_in_c(cmplwi)
  #define PPC_LCMP	stringify_in_c(cmpw)

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 3e2e37e6ecab..af25db6e0205 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S

@@ -238,7 +238,9 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
  	/* Note: this uses SWITCH_FRAME_SIZE rather than INT_FRAME_SIZE
  	   because we don't need to leave the 288-byte ABI gap at the
  	   top of the kernel stack. */
-	addi	r7,r7,THREAD_SIZE-SWITCH_FRAME_SIZE
+	li	r9,0
+	ori	r9,r9,THREAD_SIZE-SWITCH_FRAME_SIZE
+	add	r7,r7,r9

  
  	/*
  	 * PMU interrupts in radix may come in here. They will use r1, not

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 9ede61a5a469..098cf6adceec 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c

@@ -204,7 +204,9 @@ static __always_inline void call_do_softirq(const void *sp)
  {
  	/* Temporarily switch r1 to sp, call __do_softirq() then restore r1. */
  	asm volatile (
-		 PPC_STLU "	%%r1, %[offset](%[sp])	;"
+		"li		%%r0, 0			;"
+		"ori		%%r0, %%r0, %[offset]	;"

+		 PPC_STLUX "	%%r1, %[sp], %%r0	;"
  		"mr		%%r1, %[sp]		;"
  		"bl		%[callee]		;"
  		 PPC_LL "	%%r1, 0(%%r1)		;"

@@ -256,7 +258,9 @@ static __always_inline void call_do_irq(struct pt_regs *regs, void *sp)
  
  	/* Temporarily switch r1 to sp, call __do_irq() then restore r1. */
  	asm volatile (
-		 PPC_STLU "	%%r1, %[offset](%[sp])	;"
+		"li		%%r0, 0			;"
+		"ori		%%r0, %%r0, %[offset]	;"
+		 PPC_STLUX "	%%r1, %[sp], %%r0	;"

  		"mr		%%r4, %%r1		;"
  		"mr		%%r1, %[sp]		;"
  		"bl		%[callee]		;"

diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S
index 36184cada00b..ff71b98500a3 100644
--- a/arch/powerpc/kernel/misc_64.S
+++ b/arch/powerpc/kernel/misc_64.S

@@ -384,7 +384,9 @@ _GLOBAL(kexec_sequence)
  	std	r0,16(r1)
  
  	/* switch stacks to newstack -- &kexec_stack.stack */
-	stdu	r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)
+	li	r0,0
+	ori	r0,r0,THREAD_SIZE-STACK_FRAME_OVERHEAD
+	stdux	r1,r3,r0

  	mr	r1,r3
  
  	li	r0,0

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 37f50861dd98..d05e3d324f4d 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S

@@ -2686,7 +2686,8 @@ kvmppc_bad_host_intr:
  	mr	r9, r1
  	std	r1, PACAR1(r13)
  	ld	r1, PACAEMERGSP(r13)
-	subi	r1, r1, THREAD_SIZE/2 + INT_FRAME_SIZE
+	subi	r1, r1, THREAD_SIZE/2
+	subi	r1, r1, INT_FRAME_SIZE