2.6.32-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Ed Swierk <[email protected]> commit e967ef022e00bb7c2e5b1a42007abfdd52055050 upstream. When 32-bit MIPS userspace invokes a syscall indirectly via syscall(number, arg1, ..., arg7), the kernel looks up the actual syscall based on the given number, shifts the other arguments to the left, and jumps to the syscall. If the syscall is interrupted by a signal and indicates it needs to be restarted by the kernel (by returning ERESTARTNOINTR for example), the syscall must be called directly, since the number is no longer the first argument, and the other arguments are now staged for a direct call. Before shifting the arguments, store the syscall number in pt_regs->regs[2]. This gets copied temporarily into pt_regs->regs[0] after the syscall returns. If the syscall needs to be restarted, handle_signal()/do_signal() copies the number back to pt_regs->reg[2], which ends up in $v0 once control returns to userspace. Signed-off-by: Ed Swierk <[email protected]> Cc: [email protected] Patchwork: https://patchwork.linux-mips.org/patch/8929/ Signed-off-by: Ralf Baechle <[email protected]> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <[email protected]> (cherry picked from commit 08f865bba9c705aef95268a33393698e5385587e) Signed-off-by: Willy Tarreau <[email protected]> --- arch/mips/kernel/scall32-o32.S | 1 + arch/mips/kernel/scall64-o32.S | 1 + 2 files changed, 2 insertions(+) diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S index b72c554..44194c1 100644 --- a/arch/mips/kernel/scall32-o32.S +++ b/arch/mips/kernel/scall32-o32.S @@ -194,6 +194,7 @@ illegal_syscall: sll t1, t0, 3 beqz v0, einval lw t2, sys_call_table(t1) # syscall routine + sw a0, PT_R2(sp) # call routine directly on restart /* Some syscalls like execve get their arguments from struct pt_regs and claim zero arguments in the syscall table. Thus we have to diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S index 33ed571..1f7c01f 100644 --- a/arch/mips/kernel/scall64-o32.S +++ b/arch/mips/kernel/scall64-o32.S @@ -180,6 +180,7 @@ LEAF(sys32_syscall) dsll t1, t0, 3 beqz v0, einval ld t2, sys_call_table(t1) # syscall routine + sd a0, PT_R2(sp) # call routine directly on restart move a0, a1 # shift argument registers move a1, a2 -- 1.7.12.2.21.g234cd45.dirty
