powerpc/64e: provide an addressing macro for use with TOC in alternate register

The interrupt entry code carefully saves a minimal number of registers,
so in some places the TOC is required, it is loaded into a different
register, so provide a macro that can supply an alternate TOC register.

This continues to use got addressing because TOC-relative results in
"got/toc optimization is not supported" messages by the linker. Having
r2 be one of the saved registers and using that for TOC addressing may
be the best way to avoid that and switch this to TOC addressing.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220926034057.2360083-6-npiggin@gmail.com

3 files changed, 19 insertions, 8 deletions

diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index cf6bec9770d6..753a2757bcd4 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -346,6 +346,17 @@ n:
 	addis	reg,r2,name@toc@ha;		\
 	addi	reg,reg,name@toc@l
 
+#ifdef CONFIG_PPC_BOOK3E_64
+/*
+ * This is used in register-constrained interrupt handlers. Not to be used
+ * by BOOK3S. ld complains with "got/toc optimization is not supported" if r2
+ * is not used for the TOC offset, so use @got(tocreg). If the interrupt
+ * handlers saved r2 instead, LOAD_REG_ADDR could be used.
+ */
+#define LOAD_REG_ADDR_ALTTOC(reg,tocreg,name)	\
+	ld	reg,name@got(tocreg)
+#endif
+
 #define LOAD_REG_ADDRBASE(reg,name)	LOAD_REG_ADDR(reg,name)
 #define ADDROFF(name)			0
 
diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index ece1bd2a4a39..930e36099015 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -688,8 +688,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
 
 #ifdef CONFIG_RELOCATABLE
 	__LOAD_PACA_TOC(r15)
-	ld	r14,interrupt_base_book3e@got(r15)
-	ld	r15,__end_interrupts@got(r15)
+	LOAD_REG_ADDR_ALTTOC(r14, r15, interrupt_base_book3e)
+	LOAD_REG_ADDR_ALTTOC(r15, r15, __end_interrupts)
 	cmpld	cr0,r10,r14
 	cmpld	cr1,r10,r15
 #else
@@ -759,8 +759,8 @@ kernel_dbg_exc:
 
 #ifdef CONFIG_RELOCATABLE
 	__LOAD_PACA_TOC(r15)
-	ld	r14,interrupt_base_book3e@got(r15)
-	ld	r15,__end_interrupts@got(r15)
+	LOAD_REG_ADDR_ALTTOC(r14, r15, interrupt_base_book3e)
+	LOAD_REG_ADDR_ALTTOC(r15, r15, __end_interrupts)
 	cmpld	cr0,r10,r14
 	cmpld	cr1,r10,r15
 #else
@@ -884,8 +884,8 @@ kernel_dbg_exc:
 .macro SEARCH_RESTART_TABLE
 #ifdef CONFIG_RELOCATABLE
 	__LOAD_PACA_TOC(r11)
-	ld	r14,__start___restart_table@got(r11)
-	ld	r15,__stop___restart_table@got(r11)
+	LOAD_REG_ADDR_ALTTOC(r14, r11, __start___restart_table)
+	LOAD_REG_ADDR_ALTTOC(r15, r11, __stop___restart_table)
 #else
 	LOAD_REG_IMMEDIATE_SYM(r14, r11, __start___restart_table)
 	LOAD_REG_IMMEDIATE_SYM(r15, r11, __stop___restart_table)
@@ -1303,7 +1303,7 @@ a2_tlbinit_after_linear_map:
 	/* Now we branch the new virtual address mapped by this entry */
 #ifdef CONFIG_RELOCATABLE
 	__LOAD_PACA_TOC(r5)
-	ld	r3,1f@got(r5)
+	LOAD_REG_ADDR_ALTTOC(r3, r5, 1f)
 #else
 	LOAD_REG_IMMEDIATE_SYM(r3, r5, 1f)
 #endif
diff --git a/arch/powerpc/mm/nohash/tlb_low_64e.S b/arch/powerpc/mm/nohash/tlb_low_64e.S
index b3b3dfeec8f5..76cf456d7976 100644
--- a/arch/powerpc/mm/nohash/tlb_low_64e.S
+++ b/arch/powerpc/mm/nohash/tlb_low_64e.S
@@ -1119,7 +1119,7 @@ tlb_load_linear:
 	 * final implementation, especially when dealing with hypervisors
 	 */
 	__LOAD_PACA_TOC(r11)
-	ld	r11,linear_map_top@got(r11)
+	LOAD_REG_ADDR_ALTTOC(r11, r11, linear_map_top)
 	ld	r10,0(r11)
 	tovirt(10,10)
 	cmpld	cr0,r16,r10