[tip:x86/asm] x86/entry/64: Call all native slow-path syscalls with full pt-regs

From: tip-bot for Andy Lutomirski
Date: Fri Jan 29 2016 - 06:37:19 EST

Commit-ID: 46eabf06c04a6847a694a0c1413d4ac57e5b058a
Gitweb: http://git.kernel.org/tip/46eabf06c04a6847a694a0c1413d4ac57e5b058a
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Thu, 28 Jan 2016 15:11:26 -0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 29 Jan 2016 09:46:38 +0100

x86/entry/64: Call all native slow-path syscalls with full pt-regs

This removes all of the remaining asm syscall stubs except for
stub_ptregs_64. Entries in the main syscall table are now all
callable from C.

The resulting asm is every bit as ridiculous as it looks. The
next few patches will clean it up. This patch is here to let
reviewers rest their brains and for bisection.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/a6b3801be0d505d50aefabda02d3b93efbfc9c73.1454022279.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/entry/entry_64.S | 79 +---------------------------------
arch/x86/entry/syscalls/syscall_64.tbl | 18 ++++----
2 files changed, 10 insertions(+), 87 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index f1c8f15..f7050a5 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -253,7 +253,6 @@ tracesys:
* the value it wants us to use in the table lookup.
*/
RESTORE_C_REGS_EXCEPT_RAX
- RESTORE_EXTRA_REGS
#if __SYSCALL_MASK == ~0
cmpq $__NR_syscall_max, %rax
#else
@@ -264,6 +263,7 @@ tracesys:
movq %r10, %rcx /* fixup for C */
call *sys_call_table(, %rax, 8)
movq %rax, RAX(%rsp)
+ RESTORE_EXTRA_REGS
1:
/* Use IRET because user could have changed pt_regs->foo */

@@ -384,83 +384,6 @@ END(ptregs_\func)
#define __SYSCALL_64(nr, sym, qual) __SYSCALL_64_QUAL_##qual(sym)
#include <asm/syscalls_64.h>

- .macro FORK_LIKE func
-ENTRY(stub_\func)
- SAVE_EXTRA_REGS 8
- jmp sys_\func
-END(stub_\func)
- .endm
-
- FORK_LIKE clone
- FORK_LIKE fork
- FORK_LIKE vfork
-
-ENTRY(stub_execve)
- call sys_execve
-return_from_execve:
- testl %eax, %eax
- jz 1f
- /* exec failed, can use fast SYSRET code path in this case */
- ret
-1:
- /* must use IRET code path (pt_regs->cs may have changed) */
- addq $8, %rsp
- ZERO_EXTRA_REGS
- movq %rax, RAX(%rsp)
- jmp int_ret_from_sys_call
-END(stub_execve)
-/*
- * Remaining execve stubs are only 7 bytes long.
- * ENTRY() often aligns to 16 bytes, which in this case has no benefits.
- */
- .align 8
-GLOBAL(stub_execveat)
- call sys_execveat
- jmp return_from_execve
-END(stub_execveat)
-
-#if defined(CONFIG_X86_X32_ABI)
- .align 8
-GLOBAL(stub_x32_execve)
- call compat_sys_execve
- jmp return_from_execve
-END(stub_x32_execve)
- .align 8
-GLOBAL(stub_x32_execveat)
- call compat_sys_execveat
- jmp return_from_execve
-END(stub_x32_execveat)
-#endif
-
-/*
- * sigreturn is special because it needs to restore all registers on return.
- * This cannot be done with SYSRET, so use the IRET return path instead.
- */
-ENTRY(stub_rt_sigreturn)
- /*
- * SAVE_EXTRA_REGS result is not normally needed:
- * sigreturn overwrites all pt_regs->GPREGS.
- * But sigreturn can fail (!), and there is no easy way to detect that.
- * To make sure RESTORE_EXTRA_REGS doesn't restore garbage on error,
- * we SAVE_EXTRA_REGS here.
- */
- SAVE_EXTRA_REGS 8
- call sys_rt_sigreturn
-return_from_stub:
- addq $8, %rsp
- RESTORE_EXTRA_REGS
- movq %rax, RAX(%rsp)
- jmp int_ret_from_sys_call
-END(stub_rt_sigreturn)
-
-#ifdef CONFIG_X86_X32_ABI
-ENTRY(stub_x32_rt_sigreturn)
- SAVE_EXTRA_REGS 8
- call sys32_x32_rt_sigreturn
- jmp return_from_stub
-END(stub_x32_rt_sigreturn)
-#endif
-
/*
* A newly forked process directly context switches into this address.
*
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 5de342a..dcf107c 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -21,7 +21,7 @@
12 common brk sys_brk
13 64 rt_sigaction sys_rt_sigaction
14 common rt_sigprocmask sys_rt_sigprocmask
-15 64 rt_sigreturn stub_rt_sigreturn/ptregs
+15 64 rt_sigreturn sys_rt_sigreturn/ptregs
16 64 ioctl sys_ioctl
17 common pread64 sys_pread64
18 common pwrite64 sys_pwrite64
@@ -62,10 +62,10 @@
53 common socketpair sys_socketpair
54 64 setsockopt sys_setsockopt
55 64 getsockopt sys_getsockopt
-56 common clone stub_clone/ptregs
-57 common fork stub_fork/ptregs
-58 common vfork stub_vfork/ptregs
-59 64 execve stub_execve/ptregs
+56 common clone sys_clone/ptregs
+57 common fork sys_fork/ptregs
+58 common vfork sys_vfork/ptregs
+59 64 execve sys_execve/ptregs
60 common exit sys_exit
61 common wait4 sys_wait4
62 common kill sys_kill
@@ -328,7 +328,7 @@
319 common memfd_create sys_memfd_create
320 common kexec_file_load sys_kexec_file_load
321 common bpf sys_bpf
-322 64 execveat stub_execveat/ptregs
+322 64 execveat sys_execveat/ptregs
323 common userfaultfd sys_userfaultfd
324 common membarrier sys_membarrier
325 common mlock2 sys_mlock2
@@ -339,14 +339,14 @@
# for native 64-bit operation.
#
512 x32 rt_sigaction compat_sys_rt_sigaction
-513 x32 rt_sigreturn stub_x32_rt_sigreturn
+513 x32 rt_sigreturn sys32_x32_rt_sigreturn
514 x32 ioctl compat_sys_ioctl
515 x32 readv compat_sys_readv
516 x32 writev compat_sys_writev
517 x32 recvfrom compat_sys_recvfrom
518 x32 sendmsg compat_sys_sendmsg
519 x32 recvmsg compat_sys_recvmsg
-520 x32 execve stub_x32_execve/ptregs
+520 x32 execve compat_sys_execve/ptregs
521 x32 ptrace compat_sys_ptrace
522 x32 rt_sigpending compat_sys_rt_sigpending
523 x32 rt_sigtimedwait compat_sys_rt_sigtimedwait
@@ -371,4 +371,4 @@
542 x32 getsockopt compat_sys_getsockopt
543 x32 io_setup compat_sys_io_setup
544 x32 io_submit compat_sys_io_submit
-545 x32 execveat stub_x32_execveat/ptregs
+545 x32 execveat compat_sys_execveat/ptregs