I broke this recently when I changed pt_regs->r8..r11 clearing logic
in INT 80 code path.
There is a branch from SYSENTER/SYSCALL code to INT 80 code:
if we fail to retrieve arg6, we return EFAULT. Before this patch,
in this case we don't clear pt_regs->r8..r11.
This patch fixes this. The resulting code is smaller and simpler.
While at it, remove incorrect comment about syscall dispatching CALL insn:
it does not use RIP-relative addressing form (the comment was meant to be
"TODO: make this rip-relative", and morphed since then, dropping "TODO").
Signed-off-by: Denys Vlasenko <dvlas...@redhat.com>
CC: Linus Torvalds <torva...@linux-foundation.org>
CC: Steven Rostedt <rost...@goodmis.org>
CC: Ingo Molnar <mi...@kernel.org>
CC: Borislav Petkov <b...@alien8.de>
CC: "H. Peter Anvin" <h...@zytor.com>
CC: Andy Lutomirski <l...@amacapital.net>
CC: Oleg Nesterov <o...@redhat.com>
CC: Frederic Weisbecker <fweis...@gmail.com>
CC: Alexei Starovoitov <a...@plumgrid.com>
CC: Will Drewry <w...@chromium.org>
CC: Kees Cook <keesc...@chromium.org>
CC: x...@kernel.org
CC: linux-kernel@vger.kernel.org
---
arch/x86/entry/entry_64_compat.S | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 9558dac..b80f8d4 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -413,9 +413,7 @@ END(ia32_cstar_target)
ia32_badarg:
ASM_CLAC
- movq $-EFAULT, %rax
- jmp ia32_sysret
-
+ movq $-EFAULT, RAX(%rsp)
ia32_ret_from_sys_call:
xorl %eax, %eax /* Do not leak kernel information */
movq %rax, R11(%rsp)
@@ -486,9 +484,7 @@ ia32_do_call:
cmpq $(IA32_NR_syscalls-1), %rax
ja 1f
- call *ia32_sys_call_table(, %rax, 8) /* RIP relative */
-
-ia32_sysret:
+ call *ia32_sys_call_table(, %rax, 8)
movq %rax, RAX(%rsp)
1:
jmp int_ret_from_sys_call
--
1.8.1.4
--
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