powerpc: Fixup lwsync at runtime

To allow for a single kernel image on e500 v1/v2/mc we need to fixup lwsync
at runtime.  On e500v1/v2 lwsync causes an illop so we need to patch up
the code.  We default to 'sync' since that is always safe and if the cpu
is capable we will replace 'sync' with 'lwsync'.

We introduce CPU_FTR_LWSYNC as a way to determine at runtime if this is
needed.  This flag could be moved elsewhere since we dont really use it
for the normal CPU_FTR purpose.

Finally we only store the relative offset in the fixup section to keep it
as small as possible rather than using a full fixup_entry.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

9 files changed, 85 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index 40dd52d81c18..af07003573c4 100644
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c
@@ -86,6 +86,12 @@ int module_finalize(const Elf_Ehdr *hdr,
 				  (void *)sect->sh_addr + sect->sh_size);
 #endif
 
+	sect = find_section(hdr, sechdrs, "__lwsync_fixup");
+	if (sect != NULL)
+		do_lwsync_fixups(cur_cpu_spec->cpu_features,
+				 (void *)sect->sh_addr,
+				 (void *)sect->sh_addr + sect->sh_size);
+
 	return 0;
 }
 
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index 9e83add54290..0109e7f0ccf9 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -101,6 +101,10 @@ unsigned long __init early_init(unsigned long dt_ptr)
 			  PTRRELOC(&__start___ftr_fixup),
 			  PTRRELOC(&__stop___ftr_fixup));
 
+	do_lwsync_fixups(spec->cpu_features,
+			 PTRRELOC(&__start___lwsync_fixup),
+			 PTRRELOC(&__stop___lwsync_fixup));
+
 	return KERNELBASE + offset;
 }
 
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 098fd96a394a..04d8de9f0fc6 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -363,6 +363,8 @@ void __init setup_system(void)
 			  &__start___ftr_fixup, &__stop___ftr_fixup);
 	do_feature_fixups(powerpc_firmware_features,
 			  &__start___fw_ftr_fixup, &__stop___fw_ftr_fixup);
+	do_lwsync_fixups(cur_cpu_spec->cpu_features,
+			 &__start___lwsync_fixup, &__stop___lwsync_fixup);
 
 	/*
 	 * Unflatten the device-tree passed by prom_init or kexec
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index ce245a850db2..f177c60ea766 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -571,6 +571,11 @@ static __init int vdso_fixup_features(struct lib32_elfinfo *v32,
 	if (start64)
 		do_feature_fixups(powerpc_firmware_features,
 				  start64, start64 + size64);
+
+	start64 = find_section64(v64->hdr, "__lwsync_fixup", &size64);
+	if (start64)
+		do_lwsync_fixups(cur_cpu_spec->cpu_features,
+				 start64, start64 + size64);
 #endif /* CONFIG_PPC64 */
 
 	start32 = find_section32(v32->hdr, "__ftr_fixup", &size32);
@@ -585,6 +590,11 @@ static __init int vdso_fixup_features(struct lib32_elfinfo *v32,
 				  start32, start32 + size32);
 #endif /* CONFIG_PPC64 */
 
+	start32 = find_section32(v32->hdr, "__lwsync_fixup", &size32);
+	if (start32)
+		do_lwsync_fixups(cur_cpu_spec->cpu_features,
+				 start32, start32 + size32);
+
 	return 0;
 }
 
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 271793577cdc..be3b6a41dc09 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -33,6 +33,9 @@ SECTIONS
 	. = ALIGN(8);
 	__ftr_fixup	: { *(__ftr_fixup) }
 
+	. = ALIGN(8);
+	__lwsync_fixup	: { *(__lwsync_fixup) }
+
 #ifdef CONFIG_PPC64
 	. = ALIGN(8);
 	__fw_ftr_fixup	: { *(__fw_ftr_fixup) }
diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S
index e608d1bd3bff..d0b2526dd38d 100644
--- a/arch/powerpc/kernel/vdso64/vdso64.lds.S
+++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S
@@ -35,6 +35,9 @@ SECTIONS
 	__ftr_fixup	: { *(__ftr_fixup) }
 
 	. = ALIGN(8);
+	__lwsync_fixup	: { *(__lwsync_fixup) }
+
+	. = ALIGN(8);
 	__fw_ftr_fixup	: { *(__fw_ftr_fixup) }
 
 	/*
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 3c07811989fc..6856f6c15727 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -127,6 +127,12 @@ SECTIONS
 		*(__ftr_fixup)
 		__stop___ftr_fixup = .;
 	}
+	. = ALIGN(8);
+	__lwsync_fixup : AT(ADDR(__lwsync_fixup) - LOAD_OFFSET) {
+		__start___lwsync_fixup = .;
+		*(__lwsync_fixup)
+		__stop___lwsync_fixup = .;
+	}
 #ifdef CONFIG_PPC64
 	. = ALIGN(8);
 	__fw_ftr_fixup : AT(ADDR(__fw_ftr_fixup) - LOAD_OFFSET) {
diff --git a/arch/powerpc/lib/feature-fixups-test.S b/arch/powerpc/lib/feature-fixups-test.S
index 0549be04399c..cb737484c5aa 100644
--- a/arch/powerpc/lib/feature-fixups-test.S
+++ b/arch/powerpc/lib/feature-fixups-test.S
@@ -10,6 +10,7 @@
 
 #include <asm/feature-fixups.h>
 #include <asm/ppc_asm.h>
+#include <asm/synch.h>
 
 	.text
 
@@ -725,3 +726,17 @@ MAKE_MACRO_TEST_EXPECTED(FTR);
 MAKE_MACRO_TEST(FW_FTR);
 MAKE_MACRO_TEST_EXPECTED(FW_FTR);
 #endif
+
+globl(lwsync_fixup_test)
+1:	or	1,1,1
+	LWSYNC
+globl(end_lwsync_fixup_test)
+
+globl(lwsync_fixup_test_expected_LWSYNC)
+1:	or	1,1,1
+	lwsync
+
+globl(lwsync_fixup_test_expected_SYNC)
+1:	or	1,1,1
+	sync
+
diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c
index 48e1ed89052d..4e43702b9813 100644
--- a/arch/powerpc/lib/feature-fixups.c
+++ b/arch/powerpc/lib/feature-fixups.c
@@ -110,6 +110,22 @@ void do_feature_fixups(unsigned long value, void *fixup_start, void *fixup_end)
 	}
 }
 
+void do_lwsync_fixups(unsigned long value, void *fixup_start, void *fixup_end)
+{
+	unsigned int *start, *end, *dest;
+
+	if (!(value & CPU_FTR_LWSYNC))
+		return ;
+
+	start = fixup_start;
+	end = fixup_end;
+
+	for (; start < end; start++) {
+		dest = (void *)start + *start;
+		patch_instruction(dest, PPC_LWSYNC_INSTR);
+	}
+}
+
 #ifdef CONFIG_FTR_FIXUP_SELFTEST
 
 #define check(x)	\
@@ -295,6 +311,25 @@ static void test_fw_macros(void)
 #endif
 }
 
+static void test_lwsync_macros(void)
+{
+	extern void lwsync_fixup_test;
+	extern void end_lwsync_fixup_test;
+	extern void lwsync_fixup_test_expected_LWSYNC;
+	extern void lwsync_fixup_test_expected_SYNC;
+	unsigned long size = &end_lwsync_fixup_test -
+			     &lwsync_fixup_test;
+
+	/* The fixups have already been done for us during boot */
+	if (cur_cpu_spec->cpu_features & CPU_FTR_LWSYNC) {
+		check(memcmp(&lwsync_fixup_test,
+			     &lwsync_fixup_test_expected_LWSYNC, size) == 0);
+	} else {
+		check(memcmp(&lwsync_fixup_test,
+			     &lwsync_fixup_test_expected_SYNC, size) == 0);
+	}
+}
+
 static int __init test_feature_fixups(void)
 {
 	printk(KERN_DEBUG "Running feature fixup self-tests ...\n");
@@ -307,6 +342,7 @@ static int __init test_feature_fixups(void)
 	test_alternative_case_with_external_branch();
 	test_cpu_macros();
 	test_fw_macros();
+	test_lwsync_macros();
 
 	return 0;
 }