3.16.80-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Russell King rmk+kernel@armlinux.org.uk
commit 67e15fa5b487adb9b78a92789eeff2d6ec8f5cee upstream.
When the system has high memory pressure, the page containing the instruction may be paged out. Using probe_kernel_address() means that if the page is swapped out, the resulting page fault will not be handled because page faults are disabled by this function.
Use get_user() to read the instruction instead.
Reported-by: Jing Xiangfeng jingxiangfeng@huawei.com Fixes: b255188f90e2 ("ARM: fix scheduling while atomic warning in alignment handling code") Signed-off-by: Russell King rmk+kernel@armlinux.org.uk [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/arm/mm/alignment.c | 44 +++++++++++++++++++++++++++++++++-------- 1 file changed, 36 insertions(+), 8 deletions(-)
--- a/arch/arm/mm/alignment.c +++ b/arch/arm/mm/alignment.c @@ -746,6 +746,36 @@ do_alignment_t32_to_handler(unsigned lon return NULL; }
+static int alignment_get_arm(struct pt_regs *regs, u32 *ip, unsigned long *inst) +{ + u32 instr = 0; + int fault; + + if (user_mode(regs)) + fault = get_user(instr, ip); + else + fault = probe_kernel_address(ip, instr); + + *inst = __mem_to_opcode_arm(instr); + + return fault; +} + +static int alignment_get_thumb(struct pt_regs *regs, u16 *ip, u16 *inst) +{ + u16 instr = 0; + int fault; + + if (user_mode(regs)) + fault = get_user(instr, ip); + else + fault = probe_kernel_address(ip, instr); + + *inst = __mem_to_opcode_thumb16(instr); + + return fault; +} + static int do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs) { @@ -753,10 +783,10 @@ do_alignment(unsigned long addr, unsigne unsigned long instr = 0, instrptr; int (*handler)(unsigned long addr, unsigned long instr, struct pt_regs *regs); unsigned int type; - unsigned int fault; u16 tinstr = 0; int isize = 4; int thumb2_32b = 0; + int fault;
if (interrupts_enabled(regs)) local_irq_enable(); @@ -765,15 +795,14 @@ do_alignment(unsigned long addr, unsigne
if (thumb_mode(regs)) { u16 *ptr = (u16 *)(instrptr & ~1); - fault = probe_kernel_address(ptr, tinstr); - tinstr = __mem_to_opcode_thumb16(tinstr); + + fault = alignment_get_thumb(regs, ptr, &tinstr); if (!fault) { if (cpu_architecture() >= CPU_ARCH_ARMv7 && IS_T32(tinstr)) { /* Thumb-2 32-bit */ - u16 tinst2 = 0; - fault = probe_kernel_address(ptr + 1, tinst2); - tinst2 = __mem_to_opcode_thumb16(tinst2); + u16 tinst2; + fault = alignment_get_thumb(regs, ptr + 1, &tinst2); instr = __opcode_thumb32_compose(tinstr, tinst2); thumb2_32b = 1; } else { @@ -782,8 +811,7 @@ do_alignment(unsigned long addr, unsigne } } } else { - fault = probe_kernel_address(instrptr, instr); - instr = __mem_to_opcode_arm(instr); + fault = alignment_get_arm(regs, (void *)instrptr, &instr); }
if (fault) {