From 034058aa04eec66c00d6f7956aa5c7ec638eb750 Mon Sep 17 00:00:00 2001 From: jhb Date: Wed, 11 Nov 2015 01:32:35 +0000 Subject: [PATCH] MFC 284324,290164: Workaround debuggers that try to read the full 32-bit words holding selectors in trapframes. 284324: Ensure that the upper 16 bits of segment registers manually saved in trapframes are cleared by explicitly pushing a zero and then moving the segment register into the low 16 bits. Certain Intel processors treat a push of a segment register as a move of the segment register into the low 16 bits leaving the upper 16 bits of the word in the stack unchanged. 290164: Use movw instead of movl (or plain mov) when moving segment registers into memory. This is a nop on clang's assembler, but some assemblers complain if the size suffix is incorrect. git-svn-id: svn://svn.freebsd.org/base/stable/10@290668 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f --- sys/i386/i386/exception.s | 36 ++++++++++++++++++++++++------------ sys/i386/include/asmacros.h | 9 ++++++--- 2 files changed, 30 insertions(+), 15 deletions(-) diff --git a/sys/i386/i386/exception.s b/sys/i386/i386/exception.s index 58cd3e8c6..9386ada76 100644 --- a/sys/i386/i386/exception.s +++ b/sys/i386/i386/exception.s @@ -158,9 +158,12 @@ IDTVEC(xmm) .type alltraps,@function alltraps: pushal - pushl %ds - pushl %es - pushl %fs + pushl $0 + movw %ds,(%esp) + pushl $0 + movw %es,(%esp) + pushl $0 + movw %fs,(%esp) alltraps_with_regs_pushed: SET_KERNEL_SREGS cld @@ -234,9 +237,12 @@ IDTVEC(lcall_syscall) pushl $7 /* sizeof "lcall 7,0" */ subl $4,%esp /* skip over tf_trapno */ pushal - pushl %ds - pushl %es - pushl %fs + pushl $0 + movw %ds,(%esp) + pushl $0 + movw %es,(%esp) + pushl $0 + movw %fs,(%esp) SET_KERNEL_SREGS cld FAKE_MCOUNT(TF_EIP(%esp)) @@ -260,9 +266,12 @@ IDTVEC(int0x80_syscall) pushl $2 /* sizeof "int 0x80" */ subl $4,%esp /* skip over tf_trapno */ pushal - pushl %ds - pushl %es - pushl %fs + pushl $0 + movw %ds,(%esp) + pushl $0 + movw %es,(%esp) + pushl $0 + movw %fs,(%esp) SET_KERNEL_SREGS cld FAKE_MCOUNT(TF_EIP(%esp)) @@ -417,13 +426,16 @@ doreti_iret: doreti_iret_fault: subl $8,%esp pushal - pushl %ds + pushl $0 + movw %ds,(%esp) .globl doreti_popl_ds_fault doreti_popl_ds_fault: - pushl %es + pushl $0 + movw %es,(%esp) .globl doreti_popl_es_fault doreti_popl_es_fault: - pushl %fs + pushl $0 + movw %fs,(%esp) .globl doreti_popl_fs_fault doreti_popl_fs_fault: sti diff --git a/sys/i386/include/asmacros.h b/sys/i386/include/asmacros.h index c1c3f645c..ef08d0375 100644 --- a/sys/i386/include/asmacros.h +++ b/sys/i386/include/asmacros.h @@ -146,9 +146,12 @@ pushl $0 ; /* dummy error code */ \ pushl $0 ; /* dummy trap type */ \ pushal ; /* 8 ints */ \ - pushl %ds ; /* save data and extra segments ... */ \ - pushl %es ; \ - pushl %fs + pushl $0 ; /* save data and extra segments ... */ \ + movw %ds,(%esp) ; \ + pushl $0 ; \ + movw %es,(%esp) ; \ + pushl $0 ; \ + movw %fs,(%esp) #define POP_FRAME \ popl %fs ; \ -- 2.45.0