Stephen,
-----Original Message-----
From: Stephen Warren [mailto:swar...@wwwdotorg.org]
Sent: Tuesday, January 9, 2018 12:52 PM
To: u-boot@lists.denx.de; Simon Glass <s...@chromium.org>; Tom Warren
<twar...@nvidia.com>; Stephen Warren <swar...@nvidia.com>
Cc: Tom Rini <tr...@konsulko.com>
Subject: [PATCH] Makefile: ensure DTB doesn't overflow into initial stack
From: Stephen Warren <swar...@nvidia.com>
With CONFIG_SYS_INIT_SP_BSS_OFFSET enabled, the initial (pre-relocation) stack
is placed some distance after bss_start. The control DTB is appended to the
U-Boot binary at bss_start. If the DTB is too large, or the SP BSS offset too
small, then the initial stack could corrupt the DTB. Enhance the Makefile to
check whether this is likely to occur.
Signed-off-by: Stephen Warren <swar...@nvidia.com>
---
This builds on top of my previous patch "ARMv8: Allow dynamic early stack
pointer". However, since all the logic is conditional and only activated if
CONFIG_SYS_INIT_SP_BSS_OFFSET is defined, it can be applied with or without
that other patch. It'd make sense to apply it afterwards and in the same branch
though, or the change won't make a lot of sense to someone reading history in
order.
I've got this in my TOT u-boot-tegra/master, ready to send a PR to TomR. But
it's delegated to him in Patchwork. Do you want me to remove it from my PR, or
leave it in?
Tom
Makefile | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/Makefile b/Makefile
index d8f419bcd900..52cd6ea72161 100644
--- a/Makefile
+++ b/Makefile
@@ -811,6 +811,10 @@ ifneq ($(CONFIG_BUILD_TARGET),) ALL-y +=
$(CONFIG_BUILD_TARGET:"%"=%) endif
+ifneq ($(CONFIG_SYS_INIT_SP_BSS_OFFSET),)
+ALL-y += init_sp_bss_offset_check
+endif
+
LDFLAGS_u-boot += $(LDFLAGS_FINAL)
# Avoid 'Not enough room for program headers' error on binutils 2.28 onwards.
@@ -939,6 +943,33 @@ binary_size_check: u-boot-nodtb.bin FORCE
fi \
fi
+ifneq ($(CONFIG_SYS_INIT_SP_BSS_OFFSET),)
+ifneq ($(CONFIG_SYS_MALLOC_F_LEN),)
+subtract_sys_malloc_f_len = space=$$(($${space} -
+$(CONFIG_SYS_MALLOC_F_LEN))) else subtract_sys_malloc_f_len = true
+endif # The 1/4 margin below is somewhat arbitrary. The likely initial
+SP usage is # so low that the DTB could probably use 90%+ of the
+available space, for # current values of CONFIG_SYS_INIT_SP_BSS_OFFSET
+at least. However, let's be # safe for now and tweak this later if
+space becomes tight.
+# A rejected alternative would be to check that some absolute minimum
+stack # space was available. However, since
+CONFIG_SYS_INIT_SP_BSS_OFFSET is # deliberately build-specific, to take
+account of build-to-build stack usage # differences due to different
+feature sets, there is no common absolute value # to check against.
+init_sp_bss_offset_check: u-boot.dtb FORCE
+ @dtb_size=$(shell wc -c u-boot.dtb | awk '{print $$1}') ; \
+ space=$(CONFIG_SYS_INIT_SP_BSS_OFFSET) ; \
+ $(subtract_sys_malloc_f_len) ; \
+ quarter_space=$$(($${space} / 4)) ; \
+ if [ $${dtb_size} -gt $${quarter_space} ]; then \
+ echo "u-boot.dtb is larger than 1 quarter of " >&2 ; \
+ echo "(CONFIG_SYS_INIT_SP_BSS_OFFSET -
CONFIG_SYS_MALLOC_F_LEN)" >&2 ; \
+ exit 1 ; \
+ fi
+endif
+
u-boot-nodtb.bin: u-boot FORCE
$(call if_changed,objcopy)
$(call DO_STATIC_RELA,$<,$@,$(CONFIG_SYS_TEXT_BASE))
--
2.15.1
--
nvpublic
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