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authorSeiichi Ikarashi <s.ikarashi@jp.fujitsu.com>2011-12-06 17:58:14 +0900
committerIngo Molnar <mingo@elte.hu>2011-12-06 10:02:38 +0100
commit1cf8343f55525c09c88da0a494a96e1b034f84e2 (patch)
tree5cb45ead7d10d3021fd2a9424c47d25eefa4201f /arch
parentcc3a1bf52a9d2808c7cd6e8f413b02b650b6b84b (diff)
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x86: Fix rflags in FAKE_STACK_FRAME
The x86_64 kernel pushes the fake kernel stack in arch/x86/kernel/entry_64.S:FAKE_STACK_FRAME, and rflags register in it does not conform to the specification. Although Intel's manual[1] says bit 1 of it shall be set to 1, this bit is cleared to 0 on pushing the fake stack. [1] Intel(R) 64 and IA-32 Architectures Software Developer's Manual Vol.1 3-21 Figure 3-8. EFLAGS Register If it is not on purpose, it is better to be fixed, because it can lead some tools misunderstanding the stack frame. For example, "crash" utility[2] actually detects it and warns you like below: RIP: ffffffff8005dfa2 RSP: ffff8104ce0c7f58 RFLAGS: 00000200 [...] bt: WARNING: possibly bogus exception frame Signed-off-by: Seiichi Ikarashi <s.ikarashi@jp.fujitsu.com> Tested-by: Masayoshi MIZUMA <m.mizuma@jp.fujitsu.com> Cc: Jan Beulich <JBeulich@suse.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/include/asm/processor-flags.h1
-rw-r--r--arch/x86/kernel/entry_64.S2
-rw-r--r--arch/x86/kernel/process.c2
3 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/include/asm/processor-flags.h b/arch/x86/include/asm/processor-flags.h
index 2dddb317bb39..f8ab3eaad128 100644
--- a/arch/x86/include/asm/processor-flags.h
+++ b/arch/x86/include/asm/processor-flags.h
@@ -6,6 +6,7 @@
* EFLAGS bits
*/
#define X86_EFLAGS_CF 0x00000001 /* Carry Flag */
+#define X86_EFLAGS_BIT1 0x00000002 /* Bit 1 - always on */
#define X86_EFLAGS_PF 0x00000004 /* Parity Flag */
#define X86_EFLAGS_AF 0x00000010 /* Auxiliary carry Flag */
#define X86_EFLAGS_ZF 0x00000040 /* Zero Flag */
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index cfad7fce6163..a20e1cb9dc87 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -221,7 +221,7 @@ ENDPROC(native_usergs_sysret64)
/*CFI_REL_OFFSET ss,0*/
pushq_cfi %rax /* rsp */
CFI_REL_OFFSET rsp,0
- pushq_cfi $X86_EFLAGS_IF /* eflags - interrupts on */
+ pushq_cfi $(X86_EFLAGS_IF|X86_EFLAGS_BIT1) /* eflags - interrupts on */
/*CFI_REL_OFFSET rflags,0*/
pushq_cfi $__KERNEL_CS /* cs */
/*CFI_REL_OFFSET cs,0*/
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ee5d4fbd53b4..15763af7bfe3 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -293,7 +293,7 @@ int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
regs.orig_ax = -1;
regs.ip = (unsigned long) kernel_thread_helper;
regs.cs = __KERNEL_CS | get_kernel_rpl();
- regs.flags = X86_EFLAGS_IF | 0x2;
+ regs.flags = X86_EFLAGS_IF | X86_EFLAGS_BIT1;
/* Ok, create the new process.. */
return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);