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| Started by | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| First post | 2015-07-28 00:40 +0200 |
| Last post | 2015-07-28 13:20 +0200 |
| Articles | 2 — 2 participants |
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Re: [PATCH 3/5] x86/asm/entry/32: Jump from SYSENTER32 to SYSCALL32 code path Andy Lutomirski <luto@amacapital.net> - 2015-07-28 00:40 +0200
Re: [PATCH 3/5] x86/asm/entry/32: Jump from SYSENTER32 to SYSCALL32 code path Denys Vlasenko <dvlasenk@redhat.com> - 2015-07-28 13:20 +0200
| From | Andy Lutomirski <luto@amacapital.net> |
|---|---|
| Date | 2015-07-28 00:40 +0200 |
| Subject | Re: [PATCH 3/5] x86/asm/entry/32: Jump from SYSENTER32 to SYSCALL32 code path |
| Message-ID | <pQZdT-7ag-3@gated-at.bofh.it> |
> Subject: [PATCH 3/5] x86/asm/entry/32: Jump from SYSENTER32 to SYSCALL32 code path
Shouldn't that be /64, not /32, or maybe /64/compat?
On Mon, Jul 27, 2015 at 1:33 PM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
> In 32-bit SYSENTER code, load arg6 into R9 instead of EBP.
> Jump to SYSCALL code path after we finish setting up pt_regs
> and clearing FLAGS_NT.
>
> This leaves most of SYSENTER32 code path inaccessible.
>
> Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
> CC: Ingo Molnar <mingo@kernel.org>
> CC: Linus Torvalds <torvalds@linux-foundation.org>
> CC: Krzysztof A. Sobiecki <sobkas@gmail.com>
> CC: Steven Rostedt <rostedt@goodmis.org>
> CC: Borislav Petkov <bp@alien8.de>
> CC: "H. Peter Anvin" <hpa@zytor.com>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Oleg Nesterov <oleg@redhat.com>
> CC: Frederic Weisbecker <fweisbec@gmail.com>
> CC: Alexei Starovoitov <ast@plumgrid.com>
> CC: Will Drewry <wad@chromium.org>
> CC: Kees Cook <keescook@chromium.org>
> CC: x86@kernel.org
> CC: linux-kernel@vger.kernel.org
> ---
> arch/x86/entry/entry_64_compat.S | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
> index df102e8..d74745a 100644
> --- a/arch/x86/entry/entry_64_compat.S
> +++ b/arch/x86/entry/entry_64_compat.S
> @@ -93,7 +93,7 @@ ENTRY(entry_SYSENTER_compat)
> * 32-bit zero extended
> */
> ASM_STAC
> -1: movl (%rbp), %ebp
> +1: movl (%rbp), %r9d
You're sticking arg6 into r9d here, I think, and then:
>
> orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
> testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
> @@ -343,6 +344,7 @@ ENTRY(entry_SYSCALL_compat)
> _ASM_EXTABLE(1b, ia32_badarg)
> ASM_CLAC
>
> +sysenter_jumps_here:
> orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
> testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
> jnz cstar_tracesys
you land here, which eventually does:
movl %ebp, %r9d /* arg6 */
What am I missing?
--Andy
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| From | Denys Vlasenko <dvlasenk@redhat.com> |
|---|---|
| Date | 2015-07-28 13:20 +0200 |
| Message-ID | <pRb5p-7Bt-49@gated-at.bofh.it> |
| In reply to | #1193538 |
On 07/28/2015 12:37 AM, Andy Lutomirski wrote:
>> Subject: [PATCH 3/5] x86/asm/entry/32: Jump from SYSENTER32 to SYSCALL32 code path
>
> Shouldn't that be /64, not /32, or maybe /64/compat?
>
> On Mon, Jul 27, 2015 at 1:33 PM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
>> In 32-bit SYSENTER code, load arg6 into R9 instead of EBP.
>> Jump to SYSCALL code path after we finish setting up pt_regs
>> and clearing FLAGS_NT.
>>
>> This leaves most of SYSENTER32 code path inaccessible.
>>
>> Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
>> CC: Ingo Molnar <mingo@kernel.org>
>> CC: Linus Torvalds <torvalds@linux-foundation.org>
>> CC: Krzysztof A. Sobiecki <sobkas@gmail.com>
>> CC: Steven Rostedt <rostedt@goodmis.org>
>> CC: Borislav Petkov <bp@alien8.de>
>> CC: "H. Peter Anvin" <hpa@zytor.com>
>> CC: Andy Lutomirski <luto@amacapital.net>
>> CC: Oleg Nesterov <oleg@redhat.com>
>> CC: Frederic Weisbecker <fweisbec@gmail.com>
>> CC: Alexei Starovoitov <ast@plumgrid.com>
>> CC: Will Drewry <wad@chromium.org>
>> CC: Kees Cook <keescook@chromium.org>
>> CC: x86@kernel.org
>> CC: linux-kernel@vger.kernel.org
>> ---
>> arch/x86/entry/entry_64_compat.S | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
>> index df102e8..d74745a 100644
>> --- a/arch/x86/entry/entry_64_compat.S
>> +++ b/arch/x86/entry/entry_64_compat.S
>> @@ -93,7 +93,7 @@ ENTRY(entry_SYSENTER_compat)
>> * 32-bit zero extended
>> */
>> ASM_STAC
>> -1: movl (%rbp), %ebp
>> +1: movl (%rbp), %r9d
>
> You're sticking arg6 into r9d here, I think, and then:
>
>
>>
>> orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
>> testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
>> @@ -343,6 +344,7 @@ ENTRY(entry_SYSCALL_compat)
>> _ASM_EXTABLE(1b, ia32_badarg)
>> ASM_CLAC
>>
>> +sysenter_jumps_here:
>> orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
>> testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
>> jnz cstar_tracesys
>
> you land here, which eventually does:
>
> movl %ebp, %r9d /* arg6 */
>
> What am I missing?
Please "git pull" from Ingo's tree. There was a revert,
arg6 is no longer held in EBP in SYSCALL code:
cstar_do_call:
/* 32-bit syscall -> 64-bit C ABI argument conversion */
movl %edi, %r8d /* arg5 */
/* r9 already loaded */ /* arg6 */
xchg %ecx, %esi /* rsi:arg2, rcx:arg4 */
movl %ebx, %edi /* arg1 */
movl %edx, %edx /* arg3 (zero extension) */
--
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