KernelCI reports that bcm2835_defconfig is no longer booting since
commit ac7c3e4ff401 ("compiler: enable CONFIG_OPTIMIZE_INLINING
forcibly") (https://lkml.org/lkml/2019/9/26/825).
I also received a regression report from Nicolas Saenz Julienne
(https://lkml.org/lkml/2019/9/27/263).
This problem has cropped up on bcm2835_defconfig because it enables
CONFIG_CC_OPTIMIZE_FOR_SIZE. The compiler tends to prefer not inlining
functions with -Os. I was able to reproduce it with other boards and
defconfig files by manually enabling CONFIG_CC_OPTIMIZE_FOR_SIZE.
The __get_user_check() specifically uses r0, r1, r2 registers.
So, uaccess_save_and_enable() and uaccess_restore() must be inlined.
Otherwise, those register assignments would be entirely dropped,
according to my analysis of the disassembly.
Prior to commit 9012d011660e ("compiler: allow all arches to enable
CONFIG_OPTIMIZE_INLINING"), the 'inline' marker was always enough for
inlining functions, except on x86.
Since that commit, all architectures can enable CONFIG_OPTIMIZE_INLINING.
So, __always_inline is now the only guaranteed way of forcible inlining.
I added __always_inline to 4 functions in the call-graph from the
__get_user_check() macro.
Fixes: 9012d011660e ("compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING")
Reported-by: "kernelci.org bot" <[email protected]>
Reported-by: Nicolas Saenz Julienne <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>
Tested-by: Nicolas Saenz Julienne <[email protected]>
---
KernelVersion: v5.4-rc1
arch/arm/include/asm/domain.h | 8 ++++----
arch/arm/include/asm/uaccess.h | 4 ++--
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/arm/include/asm/domain.h b/arch/arm/include/asm/domain.h
index 567dbede4785..f1d0a7807cd0 100644
--- a/arch/arm/include/asm/domain.h
+++ b/arch/arm/include/asm/domain.h
@@ -82,7 +82,7 @@
#ifndef __ASSEMBLY__
#ifdef CONFIG_CPU_CP15_MMU
-static inline unsigned int get_domain(void)
+static __always_inline unsigned int get_domain(void)
{
unsigned int domain;
@@ -94,7 +94,7 @@ static inline unsigned int get_domain(void)
return domain;
}
-static inline void set_domain(unsigned val)
+static __always_inline void set_domain(unsigned int val)
{
asm volatile(
"mcr p15, 0, %0, c3, c0 @ set domain"
@@ -102,12 +102,12 @@ static inline void set_domain(unsigned val)
isb();
}
#else
-static inline unsigned int get_domain(void)
+static __always_inline unsigned int get_domain(void)
{
return 0;
}
-static inline void set_domain(unsigned val)
+static __always_inline void set_domain(unsigned int val)
{
}
#endif
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 303248e5b990..98c6b91be4a8 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -22,7 +22,7 @@
* perform such accesses (eg, via list poison values) which could then
* be exploited for priviledge escalation.
*/
-static inline unsigned int uaccess_save_and_enable(void)
+static __always_inline unsigned int uaccess_save_and_enable(void)
{
#ifdef CONFIG_CPU_SW_DOMAIN_PAN
unsigned int old_domain = get_domain();
@@ -37,7 +37,7 @@ static inline unsigned int uaccess_save_and_enable(void)
#endif
}
-static inline void uaccess_restore(unsigned int flags)
+static __always_inline void uaccess_restore(unsigned int flags)
{
#ifdef CONFIG_CPU_SW_DOMAIN_PAN
/* Restore the user access mask */
--
2.17.1