[tip:x86/asm] x86/entry/64/compat: Set up full pt_regs for all compat syscalls

From: tip-bot for Andy Lutomirski
Date: Fri Oct 09 2015 - 09:10:57 EST

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Commit-ID: 8169aff611956ed360e3313e8c718f530f58f6cb
Gitweb: http://git.kernel.org/tip/8169aff611956ed360e3313e8c718f530f58f6cb
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Mon, 5 Oct 2015 17:48:05 -0700
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 9 Oct 2015 09:41:07 +0200

x86/entry/64/compat: Set up full pt_regs for all compat syscalls

This is conceptually simpler. More importantly, it eliminates
the PTREGSCALL and execve stubs, which were not compatible with
the C ABI. This means that C code can call through the compat
syscall table.

The execve stubs are a bit subtle. They did two things: they
cleared some registers and they forced slow-path return.
Neither is necessary any more: elf_common_init clears the extra
registers and start_thread calls force_iret().

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: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/f95b7f7dfaacf88a8cae85bb06226cae53769287.1444091584.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/entry/entry_64.S | 6 +----
arch/x86/entry/entry_64_compat.S | 42 +++++++++++-----------------------
arch/x86/entry/syscalls/syscall_32.tbl | 12 +++++-----
3 files changed, 20 insertions(+), 40 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 7dc2850..83ad958 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -391,20 +391,16 @@ GLOBAL(stub_execveat)
jmp return_from_execve
END(stub_execveat)

-#if defined(CONFIG_X86_X32_ABI) || defined(CONFIG_IA32_EMULATION)
+#if defined(CONFIG_X86_X32_ABI)
.align 8
GLOBAL(stub_x32_execve)
-GLOBAL(stub32_execve)
call compat_sys_execve
jmp return_from_execve
-END(stub32_execve)
END(stub_x32_execve)
.align 8
GLOBAL(stub_x32_execveat)
-GLOBAL(stub32_execveat)
call compat_sys_execveat
jmp return_from_execve
-END(stub32_execveat)
END(stub_x32_execveat)
#endif

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
index 3216e60..2c2aac5 100644
--- a/arch/x86/entry/entry_64_compat.S
+++ b/arch/x86/entry/entry_64_compat.S
@@ -219,12 +219,18 @@ ENTRY(entry_INT80_compat)
pushq %rdx /* pt_regs->dx */
pushq %rcx /* pt_regs->cx */
pushq $-ENOSYS /* pt_regs->ax */
- pushq $0 /* pt_regs->r8 */
- pushq $0 /* pt_regs->r9 */
- pushq $0 /* pt_regs->r10 */
- pushq $0 /* pt_regs->r11 */
+ xorq %r8,%r8
+ pushq %r8 /* pt_regs->r8 = 0 */
+ pushq %r8 /* pt_regs->r9 = 0 */
+ pushq %r8 /* pt_regs->r10 = 0 */
+ pushq %r8 /* pt_regs->r11 = 0 */
+ pushq %rbx /* pt_regs->rbx */
+ pushq %rbp /* pt_regs->rbp */
+ pushq %r12 /* pt_regs->r12 */
+ pushq %r13 /* pt_regs->r13 */
+ pushq %r14 /* pt_regs->r14 */
+ pushq %r15 /* pt_regs->r15 */
cld
- sub $(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */

orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
@@ -243,10 +249,10 @@ ia32_do_call:
call *ia32_sys_call_table(, %rax, 8)
movq %rax, RAX(%rsp)
1:
+ RESTORE_EXTRA_REGS
jmp int_ret_from_sys_call

ia32_tracesys:
- SAVE_EXTRA_REGS
movq %rsp, %rdi /* &pt_regs -> arg1 */
call syscall_trace_enter
/*
@@ -261,25 +267,11 @@ ia32_tracesys:
movl RSI(%rsp), %esi
movl RDI(%rsp), %edi
movl %eax, %eax /* zero extension */
- RESTORE_EXTRA_REGS
jmp ia32_do_call
END(entry_INT80_compat)

- .macro PTREGSCALL label, func
- ALIGN
-GLOBAL(\label)
- leaq \func(%rip), %rax
- jmp ia32_ptregs_common
- .endm
-
- PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn
- PTREGSCALL stub32_sigreturn, sys32_sigreturn
- PTREGSCALL stub32_fork, sys_fork
- PTREGSCALL stub32_vfork, sys_vfork
-
ALIGN
GLOBAL(stub32_clone)
- leaq sys_clone(%rip), %rax
/*
* The 32-bit clone ABI is: clone(..., int tls_val, int *child_tidptr).
* The 64-bit clone ABI is: clone(..., int *child_tidptr, int tls_val).
@@ -288,12 +280,4 @@ GLOBAL(stub32_clone)
* so we need to swap arguments here before calling it:
*/
xchg %r8, %rcx
- jmp ia32_ptregs_common
-
- ALIGN
-ia32_ptregs_common:
- SAVE_EXTRA_REGS 8
- call *%rax
- RESTORE_EXTRA_REGS 8
- ret
-END(ia32_ptregs_common)
+ jmp sys_clone
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 7663c45..caa2c71 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -8,7 +8,7 @@
#
0 i386 restart_syscall sys_restart_syscall
1 i386 exit sys_exit
-2 i386 fork sys_fork stub32_fork
+2 i386 fork sys_fork sys_fork
3 i386 read sys_read
4 i386 write sys_write
5 i386 open sys_open compat_sys_open
@@ -17,7 +17,7 @@
8 i386 creat sys_creat
9 i386 link sys_link
10 i386 unlink sys_unlink
-11 i386 execve sys_execve stub32_execve
+11 i386 execve sys_execve compat_sys_execve
12 i386 chdir sys_chdir
13 i386 time sys_time compat_sys_time
14 i386 mknod sys_mknod
@@ -125,7 +125,7 @@
116 i386 sysinfo sys_sysinfo compat_sys_sysinfo
117 i386 ipc sys_ipc compat_sys_ipc
118 i386 fsync sys_fsync
-119 i386 sigreturn sys_sigreturn stub32_sigreturn
+119 i386 sigreturn sys_sigreturn sys32_sigreturn
120 i386 clone sys_clone stub32_clone
121 i386 setdomainname sys_setdomainname
122 i386 uname sys_newuname
@@ -179,7 +179,7 @@
170 i386 setresgid sys_setresgid16
171 i386 getresgid sys_getresgid16
172 i386 prctl sys_prctl
-173 i386 rt_sigreturn sys_rt_sigreturn stub32_rt_sigreturn
+173 i386 rt_sigreturn sys_rt_sigreturn sys32_rt_sigreturn
174 i386 rt_sigaction sys_rt_sigaction compat_sys_rt_sigaction
175 i386 rt_sigprocmask sys_rt_sigprocmask
176 i386 rt_sigpending sys_rt_sigpending compat_sys_rt_sigpending
@@ -196,7 +196,7 @@
187 i386 sendfile sys_sendfile compat_sys_sendfile
188 i386 getpmsg
189 i386 putpmsg
-190 i386 vfork sys_vfork stub32_vfork
+190 i386 vfork sys_vfork sys_vfork
191 i386 ugetrlimit sys_getrlimit compat_sys_getrlimit
192 i386 mmap2 sys_mmap_pgoff
193 i386 truncate64 sys_truncate64 sys32_truncate64
@@ -364,7 +364,7 @@
355 i386 getrandom sys_getrandom
356 i386 memfd_create sys_memfd_create
357 i386 bpf sys_bpf
-358 i386 execveat sys_execveat stub32_execveat
+358 i386 execveat sys_execveat compat_sys_execveat
359 i386 socket sys_socket
360 i386 socketpair sys_socketpair
361 i386 bind sys_bind
--
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Next message: tip-bot for Andy Lutomirski: "[tip:x86/asm] x86/entry/syscalls: Move syscall table declarations into asm/syscalls.h"
Previous message: tip-bot for Andy Lutomirski: "[tip:x86/asm] x86/entry/64/compat: Remove most of the fast system call machinery"
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