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 arch/arm/config/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 in order to avoid those registers being overwritten in the callees. 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 want to keep as much compiler's freedom as possible about the inlining decision. So, I changed the function call order instead of adding __always_inline around. Call uaccess_save_and_enable() before assigning the __p ("r0"), and uaccess_restore() after evacuating the __e ("r0"). Fixes: 9012d011660e ("compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING") Reported-by: "kernelci.org bot" <b...@kernelci.org> Reported-by: Nicolas Saenz Julienne <nsaenzjulie...@suse.de> Signed-off-by: Masahiro Yamada <yamada.masah...@socionext.com> --- arch/arm/include/asm/uaccess.h | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index 303248e5b990..559f252d7e3c 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -191,11 +191,12 @@ extern int __get_user_64t_4(void *); #define __get_user_check(x, p) \ ({ \ unsigned long __limit = current_thread_info()->addr_limit - 1; \ + unsigned int __ua_flags = uaccess_save_and_enable(); \ register typeof(*(p)) __user *__p asm("r0") = (p); \ register __inttype(x) __r2 asm("r2"); \ register unsigned long __l asm("r1") = __limit; \ register int __e asm("r0"); \ - unsigned int __ua_flags = uaccess_save_and_enable(); \ + unsigned int __err; \ switch (sizeof(*(__p))) { \ case 1: \ if (sizeof((x)) >= 8) \ @@ -223,9 +224,10 @@ extern int __get_user_64t_4(void *); break; \ default: __e = __get_user_bad(); break; \ } \ - uaccess_restore(__ua_flags); \ + __err = __e; \ x = (typeof(*(p))) __r2; \ - __e; \ + uaccess_restore(__ua_flags); \ + __err; \ }) #define get_user(x, p) \ -- 2.17.1
