powerpc/misc: get rid of add_reloc_offset()

Message ID 20180417075624.962AB6C038@po15720vm.idsi0.si.c-s.fr
State Rejected
Headers show
Series
  • powerpc/misc: get rid of add_reloc_offset()
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Commit Message

Christophe Leroy April 17, 2018, 7:56 a.m.
add_reloc_offset() is almost redundant with reloc_offset()

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/include/asm/setup.h       |  3 +--
 arch/powerpc/kernel/misc.S             | 16 ----------------
 arch/powerpc/kernel/prom_init_check.sh |  2 +-
 3 files changed, 2 insertions(+), 19 deletions(-)

Comments

Paul Mackerras April 17, 2018, 9:30 a.m. | #1
On Tue, Apr 17, 2018 at 09:56:24AM +0200, Christophe Leroy wrote:
> add_reloc_offset() is almost redundant with reloc_offset()
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
>  arch/powerpc/include/asm/setup.h       |  3 +--
>  arch/powerpc/kernel/misc.S             | 16 ----------------
>  arch/powerpc/kernel/prom_init_check.sh |  2 +-
>  3 files changed, 2 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
> index 27fa52ed6d00..115e0896ffa7 100644
> --- a/arch/powerpc/include/asm/setup.h
> +++ b/arch/powerpc/include/asm/setup.h
> @@ -17,10 +17,9 @@ extern void note_scsi_host(struct device_node *, void *);
>  
>  /* Used in very early kernel initialization. */
>  extern unsigned long reloc_offset(void);
> -extern unsigned long add_reloc_offset(unsigned long);
>  extern void reloc_got2(unsigned long);
>  
> -#define PTRRELOC(x)	((typeof(x)) add_reloc_offset((unsigned long)(x)))
> +#define PTRRELOC(x)	((typeof(x)) ((unsigned long)(x) + reloc_offset()))

NAK.  This is how it used to be, and we changed it in order to prevent
gcc from making incorrect assumptions.  If you use the form with the
explicit addition, and x is the address of an array, gcc will assume
that the result is within the bounds of the array (apparently the C
standard says it can do that) and potentially generate incorrect
code.  I recall that we had an actual case where gcc was generating
incorrect code, though I don't recall the details, as this was some
time before 2002.

Paul.

Patch

diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
index 27fa52ed6d00..115e0896ffa7 100644
--- a/arch/powerpc/include/asm/setup.h
+++ b/arch/powerpc/include/asm/setup.h
@@ -17,10 +17,9 @@  extern void note_scsi_host(struct device_node *, void *);
 
 /* Used in very early kernel initialization. */
 extern unsigned long reloc_offset(void);
-extern unsigned long add_reloc_offset(unsigned long);
 extern void reloc_got2(unsigned long);
 
-#define PTRRELOC(x)	((typeof(x)) add_reloc_offset((unsigned long)(x)))
+#define PTRRELOC(x)	((typeof(x)) ((unsigned long)(x) + reloc_offset()))
 
 void check_for_initrd(void);
 void mem_topology_setup(void);
diff --git a/arch/powerpc/kernel/misc.S b/arch/powerpc/kernel/misc.S
index 384357cb8bc0..2711b10ebdb3 100644
--- a/arch/powerpc/kernel/misc.S
+++ b/arch/powerpc/kernel/misc.S
@@ -39,22 +39,6 @@  _GLOBAL(reloc_offset)
 	.align	3
 2:	PPC_LONG 1b
 
-/*
- * add_reloc_offset(x) returns x + reloc_offset().
- */
-_GLOBAL(add_reloc_offset)
-	mflr	r0
-	bl	1f
-1:	mflr	r5
-	PPC_LL	r4,(2f-1b)(r5)
-	subf	r5,r4,r5
-	add	r3,r3,r5
-	mtlr	r0
-	blr
-
-	.align	3
-2:	PPC_LONG 1b
-
 _GLOBAL(setjmp)
 	mflr	r0
 	PPC_STL	r0,0(r3)
diff --git a/arch/powerpc/kernel/prom_init_check.sh b/arch/powerpc/kernel/prom_init_check.sh
index acb6b9226352..ee9f63186b72 100644
--- a/arch/powerpc/kernel/prom_init_check.sh
+++ b/arch/powerpc/kernel/prom_init_check.sh
@@ -16,7 +16,7 @@ 
 # If you really need to reference something from prom_init.o add
 # it to the list below:
 
-WHITELIST="add_reloc_offset __bss_start __bss_stop copy_and_flush
+WHITELIST="__bss_start __bss_stop copy_and_flush
 _end enter_prom memcpy memset reloc_offset __secondary_hold
 __secondary_hold_acknowledge __secondary_hold_spinloop __start
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