diff options
| author | Seiichi Ikarashi <s.ikarashi@jp.fujitsu.com> | 2011-12-06 17:58:14 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-12-06 10:02:38 +0100 |
| commit | 1cf8343f55525c09c88da0a494a96e1b034f84e2 (patch) | |
| tree | 5cb45ead7d10d3021fd2a9424c47d25eefa4201f /arch | |
| parent | cc3a1bf52a9d2808c7cd6e8f413b02b650b6b84b (diff) | |
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.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/process.c | 2 |
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 2dddb317bb3..f8ab3eaad12 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 cfad7fce616..a20e1cb9dc8 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 ee5d4fbd53b..15763af7bfe 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, ®s, 0, NULL, NULL); |