diff options
Diffstat (limited to 'arch/alpha/kernel/entry.S')
| -rw-r--r-- | arch/alpha/kernel/entry.S | 111 |
1 files changed, 95 insertions, 16 deletions
diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S index f4d41b4538c2..fcfd06529b12 100644 --- a/arch/alpha/kernel/entry.S +++ b/arch/alpha/kernel/entry.S @@ -10,6 +10,7 @@ #include <asm/pal.h> #include <asm/errno.h> #include <asm/unistd.h> +#include <linux/errno.h> .text .set noat @@ -36,6 +37,64 @@ .endm /* + * SYSCALL_SKIP_RETURN_RESTART_GATE + * + * Used when syscall dispatch is skipped (seccomp/ptrace injected nr=-1). + * - Ensure we never return r0==-1 with a3==0 (success); convert to ENOSYS. + * - Gate whether syscall restart is allowed by preserving restart context + * only for ERESTART* returns. Result: + * $26 = 0 => restart allowed + * $26 = 1 => restart NOT allowed + * $18 = preserved syscall nr (regs->r2) if restart allowed, else 0 + */ +.macro SYSCALL_SKIP_RETURN_RESTART_GATE + /* Fix up invalid "-1 success" return state. */ + ldq $19, 72($sp) /* a3 */ + bne $19, 1f /* already error => skip fixup */ + + ldq $20, 0($sp) /* r0 */ + lda $21, -1($31) + cmpeq $20, $21, $22 + beq $22, 1f /* r0 != -1 => skip fixup */ + + + lda $20, ENOSYS($31) + stq $20, 0($sp) /* r0 = ENOSYS */ + lda $19, 1($31) + stq $19, 72($sp) /* a3 = 1 */ +1: + /* Restart gating: success is never restartable here. */ + ldq $19, 72($sp) /* a3 */ + beq $19, 3f /* success => not restartable */ + + ldq $20, 0($sp) /* r0 (positive errno if a3==1) */ + lda $21, ERESTARTSYS($31) + cmpeq $20, $21, $22 + bne $22, 2f + lda $21, ERESTARTNOINTR($31) + cmpeq $20, $21, $22 + bne $22, 2f + lda $21, ERESTARTNOHAND($31) + cmpeq $20, $21, $22 + bne $22, 2f + lda $21, ERESTART_RESTARTBLOCK($31) + cmpeq $20, $21, $22 + bne $22, 2f + +3: /* Not a restart code (or success) => restart NOT allowed. */ + addq $31, 1, $26 /* $26=1 => restart NOT allowed */ + mov 0, $18 + br 4f + +2: /* Restart allowed. */ + ldq $18, 16($sp) /* preserved syscall nr (regs->r2) */ + mov $31, $26 /* $26=0 => restart allowed */ + br 4f +4: +.endm + + +/* * This defines the normal kernel pt-regs layout. * * regs 9-15 preserved by C code @@ -425,7 +484,7 @@ CFI_START_OSF_FRAME entDbg mov $sp, $16 jsr $31, do_entDbg CFI_END_OSF_FRAME entDbg - + /* * The system call entry point is special. Most importantly, it looks * like a function call to userspace as far as clobbered registers. We @@ -435,6 +494,17 @@ CFI_END_OSF_FRAME entDbg * So much for theory. We don't take advantage of this yet. * * Note that a0-a2 are not saved by PALcode as with the other entry points. + * + * Alpha syscall ABI uses: + * - r0 for return value + * - r19 ("a3") as error indicator (0=success, 1=error; r0 holds errno) + * + * For seccomp/ptrace/generic syscall helpers we track the syscall + * number separately: + * - regs->r1: current (mutable) syscall number (may be changed or set to -1) + * - regs->r2: original syscall number for restart/rollback + * + * On entry PAL provides the syscall number in r0; copy it into r1/r2. */ .align 4 @@ -447,6 +517,10 @@ CFI_END_OSF_FRAME entDbg .cfi_rel_offset $gp, 16 entSys: SAVE_ALL + ldq $1, 0($sp) /* syscall nr from saved r0 */ + stq $1, 8($sp) /* regs->r1 = shadow syscall nr */ + stq $1, 16($sp) /* regs->r2 = restart syscall nr */ + lda $8, 0x3fff bic $sp, $8, $8 lda $4, NR_syscalls($31) @@ -462,15 +536,19 @@ entSys: .cfi_rel_offset $17, SP_OFF+32 .cfi_rel_offset $18, SP_OFF+40 #ifdef CONFIG_AUDITSYSCALL - lda $6, _TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT + lda $6, _TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP and $3, $6, $3 bne $3, strace #else - blbs $3, strace /* check for SYSCALL_TRACE in disguise */ + lda $6, _TIF_SYSCALL_TRACE | _TIF_SECCOMP + and $3, $6, $3 + bne $3, strace #endif beq $4, 1f ldq $27, 0($5) -1: jsr $26, ($27), sys_ni_syscall +1: ldq $0, 8($sp) /* syscall nr shadow (regs->r1) */ + + jsr $26, ($27), sys_ni_syscall ldgp $gp, 0($26) blt $0, $syscall_error /* the call failed */ $ret_success: @@ -509,15 +587,8 @@ ret_to_kernel: .align 3 $syscall_error: - /* - * Some system calls (e.g., ptrace) can return arbitrary - * values which might normally be mistaken as error numbers. - * Those functions must zero $0 (v0) directly in the stack - * frame to indicate that a negative return value wasn't an - * error number.. - */ - ldq $18, 0($sp) /* old syscall nr (zero if success) */ - beq $18, $ret_success + /* Restart syscall nr comes from saved r2 (preserved even if r0 overwritten). */ + ldq $18, 16($sp) /* old syscall nr for restart */ ldq $19, 72($sp) /* .. and this a3 */ subq $31, $0, $0 /* with error in v0 */ @@ -581,6 +652,8 @@ strace: jsr $26, syscall_trace_enter /* returns the syscall number */ UNDO_SWITCH_STACK + stq $0, 8($sp) /* regs->r1 = shadow syscall nr */ + /* get the arguments back.. */ ldq $16, SP_OFF+24($sp) ldq $17, SP_OFF+32($sp) @@ -589,6 +662,11 @@ strace: ldq $20, 80($sp) ldq $21, 88($sp) + /* nr == -1: internal skip-dispatch or userspace syscall(-1)? */ + lda $6, -1($31) + cmpeq $0, $6, $6 + bne $6, $strace_skip_call /* nr == -1 => dispatch */ + /* get the system call pointer.. */ lda $1, NR_syscalls($31) lda $2, sys_call_table @@ -607,6 +685,8 @@ $strace_success: stq $31, 72($sp) /* a3=0 => no error */ stq $0, 0($sp) /* save return value */ +$strace_skip_call: + SYSCALL_SKIP_RETURN_RESTART_GATE DO_SWITCH_STACK jsr $26, syscall_trace_leave UNDO_SWITCH_STACK @@ -614,8 +694,7 @@ $strace_success: .align 3 $strace_error: - ldq $18, 0($sp) /* old syscall nr (zero if success) */ - beq $18, $strace_success + ldq $18, 16($sp) /* restart syscall nr */ ldq $19, 72($sp) /* .. and this a3 */ subq $31, $0, $0 /* with error in v0 */ @@ -634,7 +713,7 @@ $strace_error: mov $31, $26 /* tell "ret_from_sys_call" we can restart */ br ret_from_sys_call CFI_END_OSF_FRAME entSys - + /* * Save and restore the switch stack -- aka the balance of the user context. */ |