powerpc/vdso: Retrieve sigtramp offsets at buildtime

This is copied from arm64.

Instead of using runtime generated signal trampoline offsets,
get offsets at buildtime.

If the said trampoline doesn't exist, build will fail. So no
need to check whether the trampoline exists or not in the VDSO.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/f8bfd6812c3e3678b1cdb4d55a52f9eb022b40d3.1601197618.git.christophe.leroy@csgroup.eu

12 files changed, 98 insertions, 12 deletions

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 86c925bfbb76..fde3dbe57bda 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -409,6 +409,21 @@ install:
 archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)
 
+ifeq ($(KBUILD_EXTMOD),)
+# We need to generate vdso-offsets.h before compiling certain files in kernel/.
+# In order to do that, we should use the archprepare target, but we can't since
+# asm-offsets.h is included in some files used to generate vdso-offsets.h, and
+# asm-offsets.h is built in prepare0, for which archprepare is a dependency.
+# Therefore we need to generate the header after prepare0 has been made, hence
+# this hack.
+prepare: vdso_prepare
+vdso_prepare: prepare0
+	$(if $(CONFIG_VDSO32),$(Q)$(MAKE) \
+		$(build)=arch/powerpc/kernel/vdso32 include/generated/vdso32-offsets.h)
+	$(if $(CONFIG_PPC64),$(Q)$(MAKE) \
+		$(build)=arch/powerpc/kernel/vdso64 include/generated/vdso64-offsets.h)
+endif
+
 archprepare: checkbin
 
 archheaders:
diff --git a/arch/powerpc/include/asm/vdso.h b/arch/powerpc/include/asm/vdso.h
index 2ff884853f97..f5257b7f17d0 100644
--- a/arch/powerpc/include/asm/vdso.h
+++ b/arch/powerpc/include/asm/vdso.h
@@ -15,6 +15,18 @@
 
 #ifndef __ASSEMBLY__
 
+#ifdef CONFIG_PPC64
+#include <generated/vdso64-offsets.h>
+#endif
+
+#ifdef CONFIG_VDSO32
+#include <generated/vdso32-offsets.h>
+#endif
+
+#define VDSO64_SYMBOL(base, name) ((unsigned long)(base) + (vdso64_offset_##name))
+
+#define VDSO32_SYMBOL(base, name) ((unsigned long)(base) + (vdso32_offset_##name))
+
 /* Offsets relative to thread->vdso_base */
 extern unsigned long vdso64_rt_sigtramp;
 extern unsigned long vdso32_sigtramp;
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index e45aafef4c5b..934cbdf6dd10 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -801,8 +801,8 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
 	}
 
 	/* Save user registers on the stack */
-	if (vdso32_rt_sigtramp && tsk->mm->context.vdso) {
-		tramp = (unsigned long)tsk->mm->context.vdso + vdso32_rt_sigtramp;
+	if (tsk->mm->context.vdso) {
+		tramp = VDSO32_SYMBOL(tsk->mm->context.vdso, sigtramp_rt32);
 	} else {
 		tramp = (unsigned long)mctx->mc_pad;
 		/* Set up the sigreturn trampoline: li r0,sigret; sc */
@@ -901,8 +901,8 @@ int handle_signal32(struct ksignal *ksig, sigset_t *oldset,
 	else
 		unsafe_save_user_regs(regs, mctx, tm_mctx, 1, failed);
 
-	if (vdso32_sigtramp && tsk->mm->context.vdso) {
-		tramp = (unsigned long)tsk->mm->context.vdso + vdso32_sigtramp;
+	if (tsk->mm->context.vdso) {
+		tramp = VDSO32_SYMBOL(tsk->mm->context.vdso, sigtramp32);
 	} else {
 		tramp = (unsigned long)mctx->mc_pad;
 		/* Set up the sigreturn trampoline: li r0,sigret; sc */
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 68e850bd5ef7..f9e4a1ac440f 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -854,8 +854,8 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 	tsk->thread.fp_state.fpscr = 0;
 
 	/* Set up to return from userspace. */
-	if (vdso64_rt_sigtramp && tsk->mm->context.vdso) {
-		regs->nip = (unsigned long)tsk->mm->context.vdso + vdso64_rt_sigtramp;
+	if (tsk->mm->context.vdso) {
+		regs->nip = VDSO64_SYMBOL(tsk->mm->context.vdso, sigtramp_rt64);
 	} else {
 		err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
 		if (err)
diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile
index a119d9f84b08..59aa2944ecae 100644
--- a/arch/powerpc/kernel/vdso32/Makefile
+++ b/arch/powerpc/kernel/vdso32/Makefile
@@ -59,6 +59,14 @@ $(obj-vdso32): %.o: %.S FORCE
 $(obj)/vgettimeofday.o: %.o: %.c FORCE
 	$(call if_changed_dep,vdso32cc)
 
+# Generate VDSO offsets using helper script
+gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
+quiet_cmd_vdsosym = VDSOSYM $@
+      cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
+
+include/generated/vdso32-offsets.h: $(obj)/vdso32.so.dbg FORCE
+	$(call if_changed,vdsosym)
+
 # actual build commands
 quiet_cmd_vdso32ld_and_check = VDSO32L $@
       cmd_vdso32ld_and_check = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) ; $(cmd_vdso_check)
diff --git a/arch/powerpc/kernel/vdso32/gen_vdso_offsets.sh b/arch/powerpc/kernel/vdso32/gen_vdso_offsets.sh
new file mode 100755
index 000000000000..c7b54a5dcd3e
--- /dev/null
+++ b/arch/powerpc/kernel/vdso32/gen_vdso_offsets.sh
@@ -0,0 +1,16 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+#
+# Match symbols in the DSO that look like VDSO_*; produce a header file
+# of constant offsets into the shared object.
+#
+# Doing this inside the Makefile will break the $(filter-out) function,
+# causing Kbuild to rebuild the vdso-offsets header file every time.
+#
+# Author: Will Deacon <will.deacon@arm.com
+#
+
+LC_ALL=C
+sed -n -e 's/^00*/0/' -e \
+'s/^\([0-9a-fA-F]*\) . VDSO_\([a-zA-Z0-9_]*\)$/\#define vdso32_offset_\2\t0x\1/p'
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 88a2976e9942..078d75c0cd24 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -164,3 +164,9 @@ VERSION
 	local: *;
 	};
 }
+
+/*
+ * Make the sigreturn code visible to the kernel.
+ */
+VDSO_sigtramp32		= __kernel_sigtramp32;
+VDSO_sigtramp_rt32	= __kernel_sigtramp_rt32;
diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile
index 29004ad1b0fb..d365810a689a 100644
--- a/arch/powerpc/kernel/vdso64/Makefile
+++ b/arch/powerpc/kernel/vdso64/Makefile
@@ -42,6 +42,14 @@ $(obj)/vdso64_wrapper.o : $(obj)/vdso64.so.dbg
 $(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64) $(obj)/vgettimeofday.o FORCE
 	$(call if_changed,vdso64ld_and_check)
 
+# Generate VDSO offsets using helper script
+gen-vdsosym := $(srctree)/$(src)/gen_vdso_offsets.sh
+quiet_cmd_vdsosym = VDSOSYM $@
+      cmd_vdsosym = $(NM) $< | $(gen-vdsosym) | LC_ALL=C sort > $@
+
+include/generated/vdso64-offsets.h: $(obj)/vdso64.so.dbg FORCE
+	$(call if_changed,vdsosym)
+
 # actual build commands
 quiet_cmd_vdso64ld_and_check = VDSO64L $@
       cmd_vdso64ld_and_check = $(CC) $(c_flags) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^); $(cmd_vdso_check)
diff --git a/arch/powerpc/kernel/vdso64/gen_vdso_offsets.sh b/arch/powerpc/kernel/vdso64/gen_vdso_offsets.sh
new file mode 100755
index 000000000000..4bf15ffd5933
--- /dev/null
+++ b/arch/powerpc/kernel/vdso64/gen_vdso_offsets.sh
@@ -0,0 +1,16 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+#
+# Match symbols in the DSO that look like VDSO_*; produce a header file
+# of constant offsets into the shared object.
+#
+# Doing this inside the Makefile will break the $(filter-out) function,
+# causing Kbuild to rebuild the vdso-offsets header file every time.
+#
+# Author: Will Deacon <will.deacon@arm.com
+#
+
+LC_ALL=C
+sed -n -e 's/^00*/0/' -e \
+'s/^\([0-9a-fA-F]*\) . VDSO_\([a-zA-Z0-9_]*\)$/\#define vdso64_offset_\2\t0x\1/p'
diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S
index e43731386469..1f06e4f730a8 100644
--- a/arch/powerpc/kernel/vdso64/vdso64.lds.S
+++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S
@@ -159,3 +159,8 @@ VERSION
 	local: *;
 	};
 }
+
+/*
+ * Make the sigreturn code visible to the kernel.
+ */
+VDSO_sigtramp_rt64	= __kernel_sigtramp_rt64;
diff --git a/arch/powerpc/perf/callchain_32.c b/arch/powerpc/perf/callchain_32.c
index b32e94047fb9..b83c47b7947f 100644
--- a/arch/powerpc/perf/callchain_32.c
+++ b/arch/powerpc/perf/callchain_32.c
@@ -59,8 +59,8 @@ static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
 {
 	if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
 		return 1;
-	if (vdso32_sigtramp && current->mm->context.vdso &&
-	    nip == (unsigned long)current->mm->context.vdso + vdso32_sigtramp)
+	if (current->mm->context.vdso &&
+	    nip == VDSO32_SYMBOL(current->mm->context.vdso, sigtramp32))
 		return 1;
 	return 0;
 }
@@ -70,8 +70,8 @@ static int is_rt_sigreturn_32_address(unsigned int nip, unsigned int fp)
 	if (nip == fp + offsetof(struct rt_signal_frame_32,
 				 uc.uc_mcontext.mc_pad))
 		return 1;
-	if (vdso32_rt_sigtramp && current->mm->context.vdso &&
-	    nip == (unsigned long)current->mm->context.vdso + vdso32_rt_sigtramp)
+	if (current->mm->context.vdso &&
+	    nip == VDSO32_SYMBOL(current->mm->context.vdso, sigtramp_rt32))
 		return 1;
 	return 0;
 }
diff --git a/arch/powerpc/perf/callchain_64.c b/arch/powerpc/perf/callchain_64.c
index 6b9c06058c33..8d0df4226328 100644
--- a/arch/powerpc/perf/callchain_64.c
+++ b/arch/powerpc/perf/callchain_64.c
@@ -68,8 +68,8 @@ static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
 {
 	if (nip == fp + offsetof(struct signal_frame_64, tramp))
 		return 1;
-	if (vdso64_rt_sigtramp && current->mm->context.vdso &&
-	    nip == (unsigned long)current->mm->context.vdso + vdso64_rt_sigtramp)
+	if (current->mm->context.vdso &&
+	    nip == VDSO64_SYMBOL(current->mm->context.vdso, sigtramp_rt64))
 		return 1;
 	return 0;
 }