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

diff --git a/arch/powerpc/include/asm/head-64.h b/arch/powerpc/include/asm/head-64.h
index 242204e..d73153b 100644 (file)
--- a/arch/powerpc/include/asm/head-64.h
+++ b/arch/powerpc/include/asm/head-64.h
@@ -98,13 +98,9 @@ start_text:
        . = 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)                             \
@@ -161,13 +157,15 @@ name:
  * - 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__ */
 

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 6f29fb7..55caeee 100644 (file)
--- 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);

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index a08c050..5c5181e 100644 (file)
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -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
 
@@ -156,7 +156,7 @@ __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
@@ -164,7 +164,7 @@ __secondary_hold:
        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
 
@@ -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
 
@@ -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 */
 

diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index 2ad2235..d318013 100644 (file)
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -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