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powerpc/64/asm: Do not reassign labels
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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
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Daniel Axtens authored and Michael Ellerman committed Dec 23, 2021
1 parent fd98395 commit d72c4a3
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Showing 4 changed files with 31 additions and 33 deletions.
12 changes: 5 additions & 7 deletions arch/powerpc/include/asm/head-64.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -98,13 +98,9 @@ linker_stub_catch: \
. = sname##_len;

#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

#define CLOSE_FIXED_SECTION(sname) \
Expand Down Expand Up @@ -161,13 +157,15 @@ end_##sname:
* - ABS_ADDR is used to find the absolute address of any symbol, from within
* a fixed section.
*/
#define DEFINE_FIXED_SYMBOL(label) \
label##_absolute = (label - fs_label + fs_start)
// define label as being _in_ sname
#define DEFINE_FIXED_SYMBOL(label, sname) \
label##_absolute = (label - start_ ## sname + sname ## _start)

#define FIXED_SYMBOL_ABS_ADDR(label) \
(label##_absolute)

#define ABS_ADDR(label) (label - fs_label + fs_start)
// find label from _within_ sname
#define ABS_ADDR(label, sname) (label - start_ ## sname + sname ## _start)

#endif /* __ASSEMBLY__ */

Expand Down
32 changes: 16 additions & 16 deletions arch/powerpc/kernel/exceptions-64s.S
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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) \
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand All @@ -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
Expand All @@ -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
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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);
Expand Down
18 changes: 9 additions & 9 deletions arch/powerpc/kernel/head_64.S
View file
Original file line number Diff line number Diff line change
Expand Up @@ -126,7 +126,7 @@ __secondary_hold_acknowledge:
. = 0x5c
.globl __run_at_load
__run_at_load:
DEFINE_FIXED_SYMBOL(__run_at_load)
DEFINE_FIXED_SYMBOL(__run_at_load, first_256B)
.long RUN_AT_LOAD_DEFAULT
#endif

Expand Down Expand Up @@ -156,15 +156,15 @@ __secondary_hold:
/* Tell the master cpu we're here */
/* Relocation is off & we are located at an address less */
/* than 0x100, so only need to grab low order offset. */
std r24,(ABS_ADDR(__secondary_hold_acknowledge))(0)
std r24,(ABS_ADDR(__secondary_hold_acknowledge, first_256B))(0)
sync

li r26,0
#ifdef CONFIG_PPC_BOOK3E
tovirt(r26,r26)
#endif
/* All secondary cpus wait here until told to start. */
100: ld r12,(ABS_ADDR(__secondary_hold_spinloop))(r26)
100: ld r12,(ABS_ADDR(__secondary_hold_spinloop, first_256B))(r26)
cmpdi 0,r12,0
beq 100b

Expand Down Expand Up @@ -649,15 +649,15 @@ __after_prom_start:
3:
#endif
/* # bytes of memory to copy */
lis r5,(ABS_ADDR(copy_to_here))@ha
addi r5,r5,(ABS_ADDR(copy_to_here))@l
lis r5,(ABS_ADDR(copy_to_here, text))@ha
addi r5,r5,(ABS_ADDR(copy_to_here, text))@l

bl copy_and_flush /* copy the first n bytes */
/* this includes the code being */
/* executed here. */
/* Jump to the copy of this code that we just made */
addis r8,r3,(ABS_ADDR(4f))@ha
addi r12,r8,(ABS_ADDR(4f))@l
addis r8,r3,(ABS_ADDR(4f, text))@ha
addi r12,r8,(ABS_ADDR(4f, text))@l
mtctr r12
bctr

Expand All @@ -669,8 +669,8 @@ p_end: .8byte _end - copy_to_here
* Now copy the rest of the kernel up to _end, add
* _end - copy_to_here to the copy limit and run again.
*/
addis r8,r26,(ABS_ADDR(p_end))@ha
ld r8,(ABS_ADDR(p_end))@l(r8)
addis r8,r26,(ABS_ADDR(p_end, text))@ha
ld r8,(ABS_ADDR(p_end, text))@l(r8)
add r5,r5,r8
5: bl copy_and_flush /* copy the rest */

Expand Down
2 changes: 1 addition & 1 deletion arch/powerpc/kernel/interrupt_64.S
View file
Original file line number Diff line number Diff line change
Expand Up @@ -695,7 +695,7 @@ interrupt_return_macro hsrr

.globl __end_soft_masked
__end_soft_masked:
DEFINE_FIXED_SYMBOL(__end_soft_masked)
DEFINE_FIXED_SYMBOL(__end_soft_masked, text)
#endif /* CONFIG_PPC_BOOK3S */

#ifdef CONFIG_PPC_BOOK3S
Expand Down

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