powerpc: Add support for relative exception tables

This halves the exception table size on 64-bit builds, and it allows
build-time sorting of exception tables to work on relocated kernels.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Minor asm fixups and bits to keep the selftests working]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

9 files changed, 34 insertions, 23 deletions

diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index 6af8852d1f7f..bf9de5575ca9 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -785,9 +785,9 @@ END_FTR_SECTION_IFCLR(CPU_FTR_601)
  */
 #define EX_TABLE(_fault, _target)               \
         stringify_in_c(.section __ex_table,"a";)\
-        PPC_LONG_ALIGN stringify_in_c(;)        \
-        PPC_LONG stringify_in_c(_fault;)        \
-        PPC_LONG stringify_in_c(_target;)       \
+        stringify_in_c(.balign 4;)              \
+        stringify_in_c(.long (_fault) - . ;)    \
+        stringify_in_c(.long (_target) - . ;)   \
         stringify_in_c(.previous)
 
 #endif /* _ASM_POWERPC_PPC_ASM_H */
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index e0b724619c4a..a15d84d59356 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -64,23 +64,30 @@
          __access_ok((__force unsigned long)(addr), (size), get_fs()))
 
 /*
- * The exception table consists of pairs of addresses: the first is the
- * address of an instruction that is allowed to fault, and the second is
+ * The exception table consists of pairs of relative addresses: the first is
+ * the address of an instruction that is allowed to fault, and the second is
  * the address at which the program should continue.  No registers are
- * modified, so it is entirely up to the continuation code to figure out
- * what to do.
+ * modified, so it is entirely up to the continuation code to figure out what
+ * to do.
  *
- * All the routines below use bits of fixup code that are out of line
- * with the main instruction path.  This means when everything is well,
- * we don't even have to jump over them.  Further, they do not intrude
- * on our cache or tlb entries.
+ * All the routines below use bits of fixup code that are out of line with the
+ * main instruction path.  This means when everything is well, we don't even
+ * have to jump over them.  Further, they do not intrude on our cache or tlb
+ * entries.
  */
 
+#define ARCH_HAS_RELATIVE_EXTABLE
+
 struct exception_table_entry {
-        unsigned long insn;
-        unsigned long fixup;
+        int insn;
+        int fixup;
 };
 
+static inline unsigned long extable_fixup(const struct exception_table_entry *x)
+{
+        return (unsigned long)&x->fixup + x->fixup;
+}
+
 /*
  * These are the main single-value transfer routines.  They automatically
  * use the right size if we just have the right pointer type.
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index e785cc9e1ecd..9479d8e360cf 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -449,7 +449,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
                  * zero, try to fix up.
                  */
                 if ((entry = search_exception_tables(regs->nip)) != NULL) {
-                        regs->nip = entry->fixup;
+                        regs->nip = extable_fixup(entry);
                         return 1;
                 }
 
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 023a462725b5..32c468b8b548 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -365,7 +365,7 @@ static inline int check_io_access(struct pt_regs *regs)
                                (*nip & 0x100)? "OUT to": "IN from",
                                regs->gpr[rb] - _IO_BASE, nip);
                         regs->msr |= MSR_RI;
-                        regs->nip = entry->fixup;
+                        regs->nip = extable_fixup(entry);
                         return 1;
                 }
         }
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index d0b137d96df1..73932f4a386e 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -512,7 +512,7 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 
         /* Are we prepared to handle this fault?  */
         if ((entry = search_exception_tables(regs->nip)) != NULL) {
-                regs->nip = entry->fixup;
+                regs->nip = extable_fixup(entry);
                 return;
         }
 
diff --git a/arch/powerpc/platforms/embedded6xx/holly.c b/arch/powerpc/platforms/embedded6xx/holly.c
index dfd310031549..0409714e8070 100644
--- a/arch/powerpc/platforms/embedded6xx/holly.c
+++ b/arch/powerpc/platforms/embedded6xx/holly.c
@@ -263,7 +263,7 @@ static int ppc750_machine_check_exception(struct pt_regs *regs)
         if ((entry = search_exception_tables(regs->nip)) != NULL) {
                 tsi108_clear_pci_cfg_error();
                 regs->msr |= MSR_RI;
-                regs->nip = entry->fixup;
+                regs->nip = extable_fixup(entry);
                 return 1;
         }
         return 0;
diff --git a/arch/powerpc/platforms/embedded6xx/mpc7448_hpc2.c b/arch/powerpc/platforms/embedded6xx/mpc7448_hpc2.c
index f97bab8e37a2..9de100e22bf3 100644
--- a/arch/powerpc/platforms/embedded6xx/mpc7448_hpc2.c
+++ b/arch/powerpc/platforms/embedded6xx/mpc7448_hpc2.c
@@ -174,7 +174,7 @@ static int mpc7448_machine_check_exception(struct pt_regs *regs)
         if ((entry = search_exception_tables(regs->nip)) != NULL) {
                 tsi108_clear_pci_cfg_error();
                 regs->msr |= MSR_RI;
-                regs->nip = entry->fixup;
+                regs->nip = extable_fixup(entry);
                 return 1;
         }
         return 0;
diff --git a/arch/powerpc/sysdev/fsl_rio.c b/arch/powerpc/sysdev/fsl_rio.c
index 87fee0c8eb21..1c41c51f22cb 100644
--- a/arch/powerpc/sysdev/fsl_rio.c
+++ b/arch/powerpc/sysdev/fsl_rio.c
@@ -111,7 +111,7 @@ int fsl_rio_mcheck_exception(struct pt_regs *regs)
                         out_be32((u32 *)(rio_regs_win + RIO_LTLEDCSR),
                                  0);
                         regs->msr |= MSR_RI;
-                        regs->nip = entry->fixup;
+                        regs->nip = extable_fixup(entry);
                         return 1;
                 }
         }
diff --git a/tools/testing/selftests/powerpc/primitives/load_unaligned_zeropad.c b/tools/testing/selftests/powerpc/primitives/load_unaligned_zeropad.c
index cd7af4e1b65a..ed3239bbfae2 100644
--- a/tools/testing/selftests/powerpc/primitives/load_unaligned_zeropad.c
+++ b/tools/testing/selftests/powerpc/primitives/load_unaligned_zeropad.c
@@ -73,19 +73,23 @@ extern char __stop___ex_table[];
 #error implement UCONTEXT_NIA
 #endif
 
+struct extbl_entry {
+        int insn;
+        int fixup;
+};
 
 static void segv_handler(int signr, siginfo_t *info, void *ptr)
 {
         ucontext_t *uc = (ucontext_t *)ptr;
         unsigned long addr = (unsigned long)info->si_addr;
         unsigned long *ip = &UCONTEXT_NIA(uc);
-        unsigned long *ex_p = (unsigned long *)__start___ex_table;
+        struct extbl_entry *entry = (struct extbl_entry *)__start___ex_table;
 
-        while (ex_p < (unsigned long *)__stop___ex_table) {
+        while (entry < (struct extbl_entry *)__stop___ex_table) {
                 unsigned long insn, fixup;
 
-                insn = *ex_p++;
-                fixup = *ex_p++;
+                insn  = (unsigned long)&entry->insn + entry->insn;
+                fixup = (unsigned long)&entry->fixup + entry->fixup;
 
                 if (insn == *ip) {
                         *ip = fixup;