riscv: Do not use fortify in early code

Early code designates the code executed when the MMU is not yet enabled,
and this comes with some limitations (see
Documentation/arch/riscv/boot.rst, section "Pre-MMU execution").

FORTIFY_SOURCE must be disabled then since it can trigger kernel panics
as reported in [1].

Reported-by: Jason Montleon <[email protected]>
Closes: https://lore.kernel.org/linux-riscv/CAJD_bPJes4QhmXY5f63GHV9B9HFkSCoaZjk-qCT2NGS7Q9HODg@mail.gmail.com/ [1]
Fixes: a35707c ("riscv: add memory-type errata for T-Head")
Fixes: 26e7aac ("riscv: Allow to downgrade paging mode from the command line")
Cc: [email protected]
Signed-off-by: Alexandre Ghiti <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

Author: Alexandre Ghiti

arch/riscv/errata/Makefile

@@ -2,6 +2,12 @@ ifdef CONFIG_RELOCATABLE
 KBUILD_CFLAGS += -fno-pie
 endif
 
+ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
+ifdef CONFIG_FORTIFY_SOURCE
+KBUILD_CFLAGS += -D__NO_FORTIFY
+endif
+endif
+
 obj-$(CONFIG_ERRATA_ANDES) += andes/
 obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
 obj-$(CONFIG_ERRATA_THEAD) += thead/

arch/riscv/kernel/Makefile

@@ -36,6 +36,11 @@ KASAN_SANITIZE_alternative.o := n
 KASAN_SANITIZE_cpufeature.o := n
 KASAN_SANITIZE_sbi_ecall.o := n
 endif
+ifdef CONFIG_FORTIFY_SOURCE
+CFLAGS_alternative.o += -D__NO_FORTIFY
+CFLAGS_cpufeature.o += -D__NO_FORTIFY
+CFLAGS_sbi_ecall.o += -D__NO_FORTIFY
+endif
 endif
 
 extra-y += vmlinux.lds

arch/riscv/kernel/pi/Makefile

@@ -16,8 +16,12 @@ KBUILD_CFLAGS	:= $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
 KBUILD_CFLAGS	+= -mcmodel=medany
 
 CFLAGS_cmdline_early.o += -D__NO_FORTIFY
-CFLAGS_lib-fdt_ro.o += -D__NO_FORTIFY
 CFLAGS_fdt_early.o += -D__NO_FORTIFY
+# lib/string.c already defines __NO_FORTIFY
+CFLAGS_ctype.o += -D__NO_FORTIFY
+CFLAGS_lib-fdt.o += -D__NO_FORTIFY
+CFLAGS_lib-fdt_ro.o += -D__NO_FORTIFY
+CFLAGS_archrandom_early.o += -D__NO_FORTIFY
 
 $(obj)/%.pi.o: OBJCOPYFLAGS := --prefix-symbols=__pi_ \
 			       --remove-section=.note.gnu.property \