[PATCH -fixes] riscv: Do not use fortify in early code

From: Alexandre Ghiti
Date: Wed Oct 09 2024 - 03:28:04 EST


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 <jmontleo@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-riscv/CAJD_bPJes4QhmXY5f63GHV9B9HFkSCoaZjk-qCT2NGS7Q9HODg@xxxxxxxxxxxxxx/ [1]
Fixes: a35707c3d850 ("riscv: add memory-type errata for T-Head")
Fixes: 26e7aacb83df ("riscv: Allow to downgrade paging mode from the command line")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
---
arch/riscv/errata/Makefile | 6 ++++++
arch/riscv/kernel/Makefile | 5 +++++
arch/riscv/kernel/pi/Makefile | 6 +++++-
3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
index 8a2739485123..f0da9d7b39c3 100644
--- a/arch/riscv/errata/Makefile
+++ b/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/
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 7f88cc4931f5..69dc8aaab3fb 100644
--- a/arch/riscv/kernel/Makefile
+++ b/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
diff --git a/arch/riscv/kernel/pi/Makefile b/arch/riscv/kernel/pi/Makefile
index d5bf1bc7de62..81d69d45c06c 100644
--- a/arch/riscv/kernel/pi/Makefile
+++ b/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 \
--
2.39.2