kernel: Activate FORTIFY_SOURCE for MIPS kernel 5.4

CONFIG_FORTIFY_SOURCE=y is already set in the generic kernel
configuration, but it is not working for MIPS on kernel 5.4, support for
MIPS was only added with kernel 5.5, other architectures like aarch64
support FORTIFY_SOURCE already since some time.

This patch adds support for FORTIFY_SOURCE to MIPS with kernel 5.4,
kernel 5.10 already supports this and needs no changes.

This backports one patch from kernel 5.5 and one fix from 5.8 to make
fortify source also work on our kernel 5.4.

The changes are not compatible with the
306-mips_mem_functions_performance.patch patch which was also removed
with kernel 5.10, probably because of the same problems. I think it is
not needed anyway as the compiler should automatically optimize the
calls to memset(), memcpy() and memmove() even when not explicitly
telling the compiler to use the build in variant.

This increases the size of an uncompressed kernel by less than 1 KB.

Acked-by: Rosen Penev <rosenp@gmail.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

1 files changed, 107 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.4/311-MIPS-Fix-exception-handler-memcpy.patch b/target/linux/generic/backport-5.4/311-MIPS-Fix-exception-handler-memcpy.patch
new file mode 100644
index 0000000000..5a6725c7a0
--- /dev/null
+++ b/target/linux/generic/backport-5.4/311-MIPS-Fix-exception-handler-memcpy.patch
@@ -0,0 +1,107 @@
+From e01c91a360793298c9e1656a61faceff01487a43 Mon Sep 17 00:00:00 2001
+From: Ben Hutchings <ben@decadent.org.uk>
+Date: Sat, 23 May 2020 23:50:34 +0800
+Subject: [PATCH] MIPS: Fix exception handler memcpy()
+
+The exception handler subroutines are declared as a single char, but
+when copied to the required addresses the copy length is 0x80.
+
+When range checks are enabled for memcpy() this results in a build
+failure, with error messages such as:
+
+In file included from arch/mips/mti-malta/malta-init.c:15:
+In function 'memcpy',
+    inlined from 'mips_nmi_setup' at arch/mips/mti-malta/malta-init.c:98:2:
+include/linux/string.h:376:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
+  376 |    __read_overflow2();
+      |    ^~~~~~~~~~~~~~~~~~
+
+Change the declarations to use type char[].
+
+Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
+Signed-off-by: YunQiang Su <syq@debian.org>
+Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
+---
+ arch/mips/loongson64/common/init.c | 4 ++--
+ arch/mips/mti-malta/malta-init.c   | 8 ++++----
+ arch/mips/pistachio/init.c         | 8 ++++----
+ 3 files changed, 10 insertions(+), 10 deletions(-)
+
+--- a/arch/mips/loongson64/common/init.c
++++ b/arch/mips/loongson64/common/init.c
+@@ -18,10 +18,10 @@ unsigned long __maybe_unused _loongson_a
+ static void __init mips_nmi_setup(void)
+ {
+ 	void *base;
+-	extern char except_vec_nmi;
++	extern char except_vec_nmi[];
+ 
+ 	base = (void *)(CAC_BASE + 0x380);
+-	memcpy(base, &except_vec_nmi, 0x80);
++	memcpy(base, except_vec_nmi, 0x80);
+ 	flush_icache_range((unsigned long)base, (unsigned long)base + 0x80);
+ }
+ 
+--- a/arch/mips/mti-malta/malta-init.c
++++ b/arch/mips/mti-malta/malta-init.c
+@@ -90,24 +90,24 @@ static void __init console_config(void)
+ static void __init mips_nmi_setup(void)
+ {
+ 	void *base;
+-	extern char except_vec_nmi;
++	extern char except_vec_nmi[];
+ 
+ 	base = cpu_has_veic ?
+ 		(void *)(CAC_BASE + 0xa80) :
+ 		(void *)(CAC_BASE + 0x380);
+-	memcpy(base, &except_vec_nmi, 0x80);
++	memcpy(base, except_vec_nmi, 0x80);
+ 	flush_icache_range((unsigned long)base, (unsigned long)base + 0x80);
+ }
+ 
+ static void __init mips_ejtag_setup(void)
+ {
+ 	void *base;
+-	extern char except_vec_ejtag_debug;
++	extern char except_vec_ejtag_debug[];
+ 
+ 	base = cpu_has_veic ?
+ 		(void *)(CAC_BASE + 0xa00) :
+ 		(void *)(CAC_BASE + 0x300);
+-	memcpy(base, &except_vec_ejtag_debug, 0x80);
++	memcpy(base, except_vec_ejtag_debug, 0x80);
+ 	flush_icache_range((unsigned long)base, (unsigned long)base + 0x80);
+ }
+ 
+--- a/arch/mips/pistachio/init.c
++++ b/arch/mips/pistachio/init.c
+@@ -83,12 +83,12 @@ phys_addr_t mips_cdmm_phys_base(void)
+ static void __init mips_nmi_setup(void)
+ {
+ 	void *base;
+-	extern char except_vec_nmi;
++	extern char except_vec_nmi[];
+ 
+ 	base = cpu_has_veic ?
+ 		(void *)(CAC_BASE + 0xa80) :
+ 		(void *)(CAC_BASE + 0x380);
+-	memcpy(base, &except_vec_nmi, 0x80);
++	memcpy(base, except_vec_nmi, 0x80);
+ 	flush_icache_range((unsigned long)base,
+ 			   (unsigned long)base + 0x80);
+ }
+@@ -96,12 +96,12 @@ static void __init mips_nmi_setup(void)
+ static void __init mips_ejtag_setup(void)
+ {
+ 	void *base;
+-	extern char except_vec_ejtag_debug;
++	extern char except_vec_ejtag_debug[];
+ 
+ 	base = cpu_has_veic ?
+ 		(void *)(CAC_BASE + 0xa00) :
+ 		(void *)(CAC_BASE + 0x300);
+-	memcpy(base, &except_vec_ejtag_debug, 0x80);
++	memcpy(base, except_vec_ejtag_debug, 0x80);
+ 	flush_icache_range((unsigned long)base,
+ 			   (unsigned long)base + 0x80);
+ }