powerpc/64/asm: Do not reassign labels

The LLVM integrated assembler really does not like us reassigning things
to the same label:

<instantiation>:7:9: error: invalid reassignment of non-absolute variable 'fs_label'

This happens across a bunch of platforms:
https://github.com/ClangBuiltLinux/linux/issues/1043
https://github.com/ClangBuiltLinux/linux/issues/1008
https://github.com/ClangBuiltLinux/linux/issues/920
https://github.com/ClangBuiltLinux/linux/issues/1050

There is no hope of getting this fixed in LLVM (see
https://github.com/ClangBuiltLinux/linux/issues/1043#issuecomment-641571200
and https://bugs.llvm.org/show_bug.cgi?id=47798#c1 )
so if we want to build with LLVM_IAS, we need to hack
around it ourselves.

For us the big problem comes from this:

\#define USE_FIXED_SECTION(sname)				\
	fs_label = start_##sname;				\
	fs_start = sname##_start;				\
	use_ftsec sname;

\#define USE_TEXT_SECTION()
	fs_label = start_text;					\
	fs_start = text_start;					\
	.text

and in particular fs_label.

This works around it by not setting those 'variables' and requiring
that users of the variables instead track for themselves what section
they are in. This isn't amazing, by any stretch, but it gets us further
in the compilation.

Note that even though users have to keep track of the section, using
a wrong one produces an error with both binutils and llvm which prevents
from using wrong section at the compile time:

llvm error example:

AS      arch/powerpc/kernel/head_64.o
<unknown>:0: error: Cannot represent a difference across sections
make[3]: *** [/home/aik/p/kernels-llvm/llvm/scripts/Makefile.build:388: arch/powerpc/kernel/head_64.o] Error 1

binutils error example:

/home/aik/p/kernels-llvm/llvm/arch/powerpc/kernel/exceptions-64s.S: Assembler messages:
/home/aik/p/kernels-llvm/llvm/arch/powerpc/kernel/exceptions-64s.S:1974: Error: can't resolve `system_call_common' {.text section} - `start_r
eal_vectors' {.head.text.real_vectors section}
make[3]: *** [/home/aik/p/kernels-llvm/llvm/scripts/Makefile.build:388: arch/powerpc/kernel/head_64.o] Error 1

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211221055904.555763-5-aik@ozlabs.ru

1 files changed, 16 insertions, 16 deletions

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 6f29fb789c9a..55caeee37c08 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -48,7 +48,7 @@
 	.balign IFETCH_ALIGN_BYTES;				\
 	.global name;						\
 	_ASM_NOKPROBE_SYMBOL(name);				\
-	DEFINE_FIXED_SYMBOL(name);				\
+	DEFINE_FIXED_SYMBOL(name, text);			\
 name:
 
 #define TRAMP_REAL_BEGIN(name)					\
@@ -76,18 +76,18 @@ name:
 	ld	reg,PACAKBASE(r13);	/* get high part of &label */	\
 	ori	reg,reg,FIXED_SYMBOL_ABS_ADDR(label)
 
-#define __LOAD_HANDLER(reg, label)					\
+#define __LOAD_HANDLER(reg, label, section)					\
 	ld	reg,PACAKBASE(r13);					\
-	ori	reg,reg,(ABS_ADDR(label))@l
+	ori	reg,reg,(ABS_ADDR(label, section))@l
 
 /*
  * Branches from unrelocated code (e.g., interrupts) to labels outside
  * head-y require >64K offsets.
  */
-#define __LOAD_FAR_HANDLER(reg, label)					\
+#define __LOAD_FAR_HANDLER(reg, label, section)					\
 	ld	reg,PACAKBASE(r13);					\
-	ori	reg,reg,(ABS_ADDR(label))@l;				\
-	addis	reg,reg,(ABS_ADDR(label))@h
+	ori	reg,reg,(ABS_ADDR(label, section))@l;				\
+	addis	reg,reg,(ABS_ADDR(label, section))@h
 
 /*
  * Interrupt code generation macros
@@ -381,7 +381,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
  * This switches to virtual mode and sets MSR[RI].
  */
 .macro __GEN_COMMON_ENTRY name
-DEFINE_FIXED_SYMBOL(\name\()_common_real)
+DEFINE_FIXED_SYMBOL(\name\()_common_real, text)
 \name\()_common_real:
 	.if IKVM_REAL
 		KVMTEST \name kvm_interrupt
@@ -404,7 +404,7 @@ DEFINE_FIXED_SYMBOL(\name\()_common_real)
 	.endif
 
 	.balign IFETCH_ALIGN_BYTES
-DEFINE_FIXED_SYMBOL(\name\()_common_virt)
+DEFINE_FIXED_SYMBOL(\name\()_common_virt, text)
 \name\()_common_virt:
 	.if IKVM_VIRT
 		KVMTEST \name kvm_interrupt
@@ -418,7 +418,7 @@ DEFINE_FIXED_SYMBOL(\name\()_common_virt)
  * want to run in real mode.
  */
 .macro __GEN_REALMODE_COMMON_ENTRY name
-DEFINE_FIXED_SYMBOL(\name\()_common_real)
+DEFINE_FIXED_SYMBOL(\name\()_common_real, text)
 \name\()_common_real:
 	.if IKVM_REAL
 		KVMTEST \name kvm_interrupt
@@ -852,12 +852,12 @@ SOFT_MASK_TABLE(0xc000000000003000, 0xc000000000004000)
 
 #ifdef CONFIG_RELOCATABLE
 TRAMP_VIRT_BEGIN(system_call_vectored_tramp)
-	__LOAD_HANDLER(r10, system_call_vectored_common)
+	__LOAD_HANDLER(r10, system_call_vectored_common, virt_trampolines)
 	mtctr	r10
 	bctr
 
 TRAMP_VIRT_BEGIN(system_call_vectored_sigill_tramp)
-	__LOAD_HANDLER(r10, system_call_vectored_sigill)
+	__LOAD_HANDLER(r10, system_call_vectored_sigill, virt_trampolines)
 	mtctr	r10
 	bctr
 #endif
@@ -961,7 +961,7 @@ TRAMP_REAL_BEGIN(system_reset_idle_wake)
 	/* We are waking up from idle, so may clobber any volatile register */
 	cmpwi	cr1,r5,2
 	bltlr	cr1	/* no state loss, return to idle caller with r3=SRR1 */
-	__LOAD_FAR_HANDLER(r12, DOTSYM(idle_return_gpr_loss))
+	__LOAD_FAR_HANDLER(r12, DOTSYM(idle_return_gpr_loss), real_trampolines)
 	mtctr	r12
 	bctr
 #endif
@@ -1960,12 +1960,12 @@ END_FTR_SECTION_IFSET(CPU_FTR_REAL_LE)
 	HMT_MEDIUM
 
 	.if ! \virt
-	__LOAD_HANDLER(r10, system_call_common_real)
+	__LOAD_HANDLER(r10, system_call_common_real, real_vectors)
 	mtctr	r10
 	bctr
 	.else
 #ifdef CONFIG_RELOCATABLE
-	__LOAD_HANDLER(r10, system_call_common)
+	__LOAD_HANDLER(r10, system_call_common, virt_vectors)
 	mtctr	r10
 	bctr
 #else
@@ -2019,7 +2019,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	 * Requires __LOAD_FAR_HANDLER beause kvmppc_hcall lives
 	 * outside the head section.
 	 */
-	__LOAD_FAR_HANDLER(r10, kvmppc_hcall)
+	__LOAD_FAR_HANDLER(r10, kvmppc_hcall, real_trampolines)
 	mtctr   r10
 	bctr
 #else
@@ -3061,7 +3061,7 @@ USE_FIXED_SECTION(virt_trampolines)
 	.align	7
 	.globl	__end_interrupts
 __end_interrupts:
-DEFINE_FIXED_SYMBOL(__end_interrupts)
+DEFINE_FIXED_SYMBOL(__end_interrupts, virt_trampolines)
 
 CLOSE_FIXED_SECTION(real_vectors);
 CLOSE_FIXED_SECTION(real_trampolines);