diff options
Diffstat (limited to 'common-user')
| -rw-r--r-- | common-user/host/aarch64/safe-syscall.inc.S | 76 | ||||
| -rw-r--r-- | common-user/host/arm/safe-syscall.inc.S | 99 | ||||
| -rw-r--r-- | common-user/host/i386/safe-syscall.inc.S | 115 | ||||
| -rw-r--r-- | common-user/host/mips/safe-syscall.inc.S | 148 | ||||
| -rw-r--r-- | common-user/host/ppc64/safe-syscall.inc.S | 94 | ||||
| -rw-r--r-- | common-user/host/riscv/safe-syscall.inc.S | 79 | ||||
| -rw-r--r-- | common-user/host/s390x/safe-syscall.inc.S | 98 | ||||
| -rw-r--r-- | common-user/host/sparc64/safe-syscall.inc.S | 89 | ||||
| -rw-r--r-- | common-user/host/x86_64/safe-syscall.inc.S | 94 | ||||
| -rw-r--r-- | common-user/meson.build | 6 | ||||
| -rw-r--r-- | common-user/safe-syscall-error.c | 25 | ||||
| -rw-r--r-- | common-user/safe-syscall.S | 27 |
12 files changed, 950 insertions, 0 deletions
diff --git a/common-user/host/aarch64/safe-syscall.inc.S b/common-user/host/aarch64/safe-syscall.inc.S new file mode 100644 index 0000000000..73a04b73b3 --- /dev/null +++ b/common-user/host/aarch64/safe-syscall.inc.S @@ -0,0 +1,76 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Written by Richard Henderson <rth@twiddle.net> + * Copyright (C) 2016 Red Hat, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, #function + .type safe_syscall_start, #function + .type safe_syscall_end, #function + + /* This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ +safe_syscall_base: + .cfi_startproc + /* The syscall calling convention isn't the same as the + * C one: + * we enter with x0 == &signal_pending + * x1 == syscall number + * x2 ... x7, (stack) == syscall arguments + * and return the result in x0 + * and the syscall instruction needs + * x8 == syscall number + * x0 ... x6 == syscall arguments + * and returns the result in x0 + * Shuffle everything around appropriately. + */ + mov x9, x0 /* signal_pending pointer */ + mov x8, x1 /* syscall number */ + mov x0, x2 /* syscall arguments */ + mov x1, x3 + mov x2, x4 + mov x3, x5 + mov x4, x6 + mov x5, x7 + ldr x6, [sp] + + /* This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* if signal_pending is non-zero, don't do the call */ + ldr w10, [x9] + cbnz w10, 2f + svc 0x0 +safe_syscall_end: + /* code path for having successfully executed the syscall */ + cmp x0, #-4096 + b.hi 0f + ret + + /* code path setting errno */ +0: neg w0, w0 + b safe_syscall_set_errno_tail + + /* code path when we didn't execute the syscall */ +2: mov w0, #QEMU_ERESTARTSYS + b safe_syscall_set_errno_tail + .cfi_endproc + .size safe_syscall_base, .-safe_syscall_base diff --git a/common-user/host/arm/safe-syscall.inc.S b/common-user/host/arm/safe-syscall.inc.S new file mode 100644 index 0000000000..66176a902c --- /dev/null +++ b/common-user/host/arm/safe-syscall.inc.S @@ -0,0 +1,99 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Written by Richard Henderson <rth@twiddle.net> + * Copyright (C) 2016 Red Hat, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, %function + + .cfi_sections .debug_frame + + .text + .syntax unified + .arm + .align 2 + + /* This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ +safe_syscall_base: + .fnstart + .cfi_startproc + mov r12, sp /* save entry stack */ + push { r4, r5, r6, r7, r8, lr } + .save { r4, r5, r6, r7, r8, lr } + .cfi_adjust_cfa_offset 24 + .cfi_rel_offset r4, 0 + .cfi_rel_offset r5, 4 + .cfi_rel_offset r6, 8 + .cfi_rel_offset r7, 12 + .cfi_rel_offset r8, 16 + .cfi_rel_offset lr, 20 + + /* The syscall calling convention isn't the same as the C one: + * we enter with r0 == &signal_pending + * r1 == syscall number + * r2, r3, [sp+0] ... [sp+12] == syscall arguments + * and return the result in r0 + * and the syscall instruction needs + * r7 == syscall number + * r0 ... r6 == syscall arguments + * and returns the result in r0 + * Shuffle everything around appropriately. + * Note the 16 bytes that we pushed to save registers. + */ + mov r8, r0 /* copy signal_pending */ + mov r7, r1 /* syscall number */ + mov r0, r2 /* syscall args */ + mov r1, r3 + ldm r12, { r2, r3, r4, r5, r6 } + + /* This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* if signal_pending is non-zero, don't do the call */ + ldr r12, [r8] /* signal_pending */ + tst r12, r12 + bne 2f + swi 0 +safe_syscall_end: + /* code path for having successfully executed the syscall */ + cmp r0, #-4096 + neghi r0, r0 + bhi 1f + pop { r4, r5, r6, r7, r8, pc } + + /* code path when we didn't execute the syscall */ +2: mov r0, #QEMU_ERESTARTSYS + + /* code path setting errno */ +1: pop { r4, r5, r6, r7, r8, lr } + .cfi_adjust_cfa_offset -24 + .cfi_restore r4 + .cfi_restore r5 + .cfi_restore r6 + .cfi_restore r7 + .cfi_restore r8 + .cfi_restore lr + b safe_syscall_set_errno_tail + + .fnend + .cfi_endproc + .size safe_syscall_base, .-safe_syscall_base diff --git a/common-user/host/i386/safe-syscall.inc.S b/common-user/host/i386/safe-syscall.inc.S new file mode 100644 index 0000000000..aced8c5141 --- /dev/null +++ b/common-user/host/i386/safe-syscall.inc.S @@ -0,0 +1,115 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Written by Richard Henderson <rth@twiddle.net> + * Copyright (C) 2016 Red Hat, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, @function + + /* This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ +safe_syscall_base: + .cfi_startproc + push %ebp + .cfi_adjust_cfa_offset 4 + .cfi_rel_offset ebp, 0 + push %esi + .cfi_adjust_cfa_offset 4 + .cfi_rel_offset esi, 0 + push %edi + .cfi_adjust_cfa_offset 4 + .cfi_rel_offset edi, 0 + push %ebx + .cfi_adjust_cfa_offset 4 + .cfi_rel_offset ebx, 0 + + /* The syscall calling convention isn't the same as the C one: + * we enter with 0(%esp) == return address + * 4(%esp) == &signal_pending + * 8(%esp) == syscall number + * 12(%esp) ... 32(%esp) == syscall arguments + * and return the result in eax + * and the syscall instruction needs + * eax == syscall number + * ebx, ecx, edx, esi, edi, ebp == syscall arguments + * and returns the result in eax + * Shuffle everything around appropriately. + * Note the 16 bytes that we pushed to save registers. + */ + mov 12+16(%esp), %ebx /* the syscall arguments */ + mov 16+16(%esp), %ecx + mov 20+16(%esp), %edx + mov 24+16(%esp), %esi + mov 28+16(%esp), %edi + mov 32+16(%esp), %ebp + + /* This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* if signal_pending is non-zero, don't do the call */ + mov 4+16(%esp), %eax /* signal_pending */ + cmpl $0, (%eax) + jnz 2f + mov 8+16(%esp), %eax /* syscall number */ + int $0x80 +safe_syscall_end: + /* code path for having successfully executed the syscall */ + cmp $-4095, %eax + jae 0f + pop %ebx + .cfi_remember_state + .cfi_adjust_cfa_offset -4 + .cfi_restore ebx + pop %edi + .cfi_adjust_cfa_offset -4 + .cfi_restore edi + pop %esi + .cfi_adjust_cfa_offset -4 + .cfi_restore esi + pop %ebp + .cfi_adjust_cfa_offset -4 + .cfi_restore ebp + ret + .cfi_restore_state + +0: neg %eax + jmp 1f + + /* code path when we didn't execute the syscall */ +2: mov $QEMU_ERESTARTSYS, %eax + + /* code path setting errno */ +1: pop %ebx + .cfi_adjust_cfa_offset -4 + .cfi_restore ebx + pop %edi + .cfi_adjust_cfa_offset -4 + .cfi_restore edi + pop %esi + .cfi_adjust_cfa_offset -4 + .cfi_restore esi + pop %ebp + .cfi_adjust_cfa_offset -4 + .cfi_restore ebp + jmp safe_syscall_set_errno_tail + + .cfi_endproc + .size safe_syscall_base, .-safe_syscall_base diff --git a/common-user/host/mips/safe-syscall.inc.S b/common-user/host/mips/safe-syscall.inc.S new file mode 100644 index 0000000000..fc75a337d1 --- /dev/null +++ b/common-user/host/mips/safe-syscall.inc.S @@ -0,0 +1,148 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Written by Richard Henderson <richard.henderson@linaro.org> + * Copyright (C) 2021 Linaro, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "sys/regdef.h" +#include "sys/asm.h" + + .text + .set nomips16 + .set reorder + + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_start, @function + .type safe_syscall_end, @function + + /* + * This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ + +#if _MIPS_SIM == _ABIO32 +/* 8 * 4 = 32 for outgoing parameters; 1 * 4 for s0 save; 1 * 4 for align. */ +#define FRAME 40 +#define OFS_S0 32 +#else +/* 1 * 8 for s0 save; 1 * 8 for align. */ +#define FRAME 16 +#define OFS_S0 0 +#endif + + +NESTED(safe_syscall_base, FRAME, ra) + .cfi_startproc + PTR_ADDIU sp, sp, -FRAME + .cfi_adjust_cfa_offset FRAME + REG_S s0, OFS_S0(sp) + .cfi_rel_offset s0, OFS_S0 +#if _MIPS_SIM == _ABIO32 + /* + * The syscall calling convention is nearly the same as C: + * we enter with a0 == &signal_pending + * a1 == syscall number + * a2, a3, stack == syscall arguments + * and return the result in a0 + * and the syscall instruction needs + * v0 == syscall number + * a0 ... a3, stack == syscall arguments + * and returns the result in v0 + * Shuffle everything around appropriately. + */ + move s0, a0 /* signal_pending pointer */ + move v0, a1 /* syscall number */ + move a0, a2 /* syscall arguments */ + move a1, a3 + lw a2, FRAME+16(sp) + lw a3, FRAME+20(sp) + lw t4, FRAME+24(sp) + lw t5, FRAME+28(sp) + lw t6, FRAME+32(sp) + lw t7, FRAME+40(sp) + sw t4, 16(sp) + sw t5, 20(sp) + sw t6, 24(sp) + sw t7, 28(sp) +#else + /* + * The syscall calling convention is nearly the same as C: + * we enter with a0 == &signal_pending + * a1 == syscall number + * a2 ... a7 == syscall arguments + * and return the result in a0 + * and the syscall instruction needs + * v0 == syscall number + * a0 ... a5 == syscall arguments + * and returns the result in v0 + * Shuffle everything around appropriately. + */ + move s0, a0 /* signal_pending pointer */ + move v0, a1 /* syscall number */ + move a0, a2 /* syscall arguments */ + move a1, a3 + move a2, a4 + move a3, a5 + move a4, a6 + move a5, a7 +#endif + + /* + * This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* If signal_pending is non-zero, don't do the call */ + lw t1, 0(s0) + bnez t1, 2f + syscall +safe_syscall_end: + + /* code path for having successfully executed the syscall */ + REG_L s0, OFS_S0(sp) + PTR_ADDIU sp, sp, FRAME + .cfi_remember_state + .cfi_adjust_cfa_offset -FRAME + .cfi_restore s0 + bnez a3, 1f + jr ra + .cfi_restore_state + + /* code path when we didn't execute the syscall */ +2: REG_L s0, OFS_S0(sp) + PTR_ADDIU sp, sp, FRAME + .cfi_adjust_cfa_offset -FRAME + .cfi_restore s0 + li v0, QEMU_ERESTARTSYS + + /* code path setting errno */ + /* + * We didn't setup GP on entry, optimistic of the syscall success. + * We must do so now to load the address of the helper, as required + * by the ABI, into t9. + * + * Note that SETUP_GPX and SETUP_GPX64 are themselves conditional, + * so we can simply let the one that's not empty succeed. + */ +1: USE_ALT_CP(t0) + SETUP_GPX(t1) + SETUP_GPX64(t0, t1) + PTR_LA t9, safe_syscall_set_errno_tail + jr t9 + + .cfi_endproc +END(safe_syscall_base) diff --git a/common-user/host/ppc64/safe-syscall.inc.S b/common-user/host/ppc64/safe-syscall.inc.S new file mode 100644 index 0000000000..947a850dfd --- /dev/null +++ b/common-user/host/ppc64/safe-syscall.inc.S @@ -0,0 +1,94 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Written by Richard Henderson <rth@twiddle.net> + * Copyright (C) 2016 Red Hat, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, @function + + .text + + /* This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ +#if _CALL_ELF == 2 +safe_syscall_base: + .cfi_startproc + .localentry safe_syscall_base,0 +#else + .section ".opd","aw" + .align 3 +safe_syscall_base: + .quad .L.safe_syscall_base,.TOC.@tocbase,0 + .previous +.L.safe_syscall_base: + .cfi_startproc +#endif + /* We enter with r3 == &signal_pending + * r4 == syscall number + * r5 ... r10 == syscall arguments + * and return the result in r3 + * and the syscall instruction needs + * r0 == syscall number + * r3 ... r8 == syscall arguments + * and returns the result in r3 + * Shuffle everything around appropriately. + */ + std 14, 16(1) /* Preserve r14 in SP+16 */ + .cfi_offset 14, 16 + mr 14, 3 /* signal_pending */ + mr 0, 4 /* syscall number */ + mr 3, 5 /* syscall arguments */ + mr 4, 6 + mr 5, 7 + mr 6, 8 + mr 7, 9 + mr 8, 10 + + /* This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* if signal_pending is non-zero, don't do the call */ + lwz 12, 0(14) + cmpwi 0, 12, 0 + bne- 2f + sc +safe_syscall_end: + /* code path when we did execute the syscall */ + ld 14, 16(1) /* restore r14 */ + bso- 1f + blr + + /* code path when we didn't execute the syscall */ +2: ld 14, 16(1) /* restore r14 */ + addi 3, 0, QEMU_ERESTARTSYS + + /* code path setting errno */ +1: b safe_syscall_set_errno_tail + nop /* per abi, for the linker to modify */ + + .cfi_endproc + +#if _CALL_ELF == 2 + .size safe_syscall_base, .-safe_syscall_base +#else + .size safe_syscall_base, .-.L.safe_syscall_base + .size .L.safe_syscall_base, .-.L.safe_syscall_base +#endif diff --git a/common-user/host/riscv/safe-syscall.inc.S b/common-user/host/riscv/safe-syscall.inc.S new file mode 100644 index 0000000000..dfe83c300e --- /dev/null +++ b/common-user/host/riscv/safe-syscall.inc.S @@ -0,0 +1,79 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Written by Richard Henderson <rth@twiddle.net> + * Copyright (C) 2018 Linaro, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, @function + .type safe_syscall_start, @function + .type safe_syscall_end, @function + + /* + * This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ +safe_syscall_base: + .cfi_startproc + /* + * The syscall calling convention is nearly the same as C: + * we enter with a0 == &signal_pending + * a1 == syscall number + * a2 ... a7 == syscall arguments + * and return the result in a0 + * and the syscall instruction needs + * a7 == syscall number + * a0 ... a5 == syscall arguments + * and returns the result in a0 + * Shuffle everything around appropriately. + */ + mv t0, a0 /* signal_pending pointer */ + mv t1, a1 /* syscall number */ + mv a0, a2 /* syscall arguments */ + mv a1, a3 + mv a2, a4 + mv a3, a5 + mv a4, a6 + mv a5, a7 + mv a7, t1 + + /* + * This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* If signal_pending is non-zero, don't do the call */ + lw t1, 0(t0) + bnez t1, 2f + scall +safe_syscall_end: + /* code path for having successfully executed the syscall */ + li t2, -4096 + bgtu a0, t2, 0f + ret + + /* code path setting errno */ +0: neg a0, a0 + j safe_syscall_set_errno_tail + + /* code path when we didn't execute the syscall */ +2: li a0, QEMU_ERESTARTSYS + j safe_syscall_set_errno_tail + + .cfi_endproc + .size safe_syscall_base, .-safe_syscall_base diff --git a/common-user/host/s390x/safe-syscall.inc.S b/common-user/host/s390x/safe-syscall.inc.S new file mode 100644 index 0000000000..2ccbaa2402 --- /dev/null +++ b/common-user/host/s390x/safe-syscall.inc.S @@ -0,0 +1,98 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Written by Richard Henderson <rth@twiddle.net> + * Copyright (C) 2016 Red Hat, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, @function + + /* This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ +safe_syscall_base: + .cfi_startproc + stmg %r6,%r15,48(%r15) /* save all call-saved registers */ + .cfi_offset %r15,-40 + .cfi_offset %r14,-48 + .cfi_offset %r13,-56 + .cfi_offset %r12,-64 + .cfi_offset %r11,-72 + .cfi_offset %r10,-80 + .cfi_offset %r9,-88 + .cfi_offset %r8,-96 + .cfi_offset %r7,-104 + .cfi_offset %r6,-112 + lgr %r1,%r15 + lg %r0,8(%r15) /* load eos */ + aghi %r15,-160 + .cfi_adjust_cfa_offset 160 + stg %r1,0(%r15) /* store back chain */ + stg %r0,8(%r15) /* store eos */ + + /* + * The syscall calling convention isn't the same as the C one: + * we enter with r2 == &signal_pending + * r3 == syscall number + * r4, r5, r6, (stack) == syscall arguments + * and return the result in r2 + * and the syscall instruction needs + * r1 == syscall number + * r2 ... r7 == syscall arguments + * and returns the result in r2 + * Shuffle everything around appropriately. + */ + lgr %r8,%r2 /* signal_pending pointer */ + lgr %r1,%r3 /* syscall number */ + lgr %r2,%r4 /* syscall args */ + lgr %r3,%r5 + lgr %r4,%r6 + lmg %r5,%r7,320(%r15) + + /* This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* if signal_pending is non-zero, don't do the call */ + icm %r0,15,0(%r8) + jne 2f + svc 0 +safe_syscall_end: + + /* code path for having successfully executed the syscall */ + lg %r15,0(%r15) /* load back chain */ + .cfi_remember_state + .cfi_adjust_cfa_offset -160 + lmg %r6,%r15,48(%r15) /* load saved registers */ + + lghi %r0, -4095 /* check for syscall error */ + clgr %r2, %r0 + blr %r14 /* return on success */ + lcr %r2, %r2 /* create positive errno */ + jg safe_syscall_set_errno_tail + .cfi_restore_state + + /* code path when we didn't execute the syscall */ +2: lg %r15,0(%r15) /* load back chain */ + .cfi_adjust_cfa_offset -160 + lmg %r6,%r15,48(%r15) /* load saved registers */ + lghi %r2, QEMU_ERESTARTSYS + jg safe_syscall_set_errno_tail + + .cfi_endproc + .size safe_syscall_base, .-safe_syscall_base diff --git a/common-user/host/sparc64/safe-syscall.inc.S b/common-user/host/sparc64/safe-syscall.inc.S new file mode 100644 index 0000000000..a2f2b9c967 --- /dev/null +++ b/common-user/host/sparc64/safe-syscall.inc.S @@ -0,0 +1,89 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Written by Richard Henderson <richard.henderson@linaro.org> + * Copyright (C) 2021 Linaro, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + + .text + .balign 4 + + .register %g2, #scratch + .register %g3, #scratch + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, @function + .type safe_syscall_start, @function + .type safe_syscall_end, @function + +#define STACK_BIAS 2047 +#define PARAM(N) STACK_BIAS + N*8 + + /* + * This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ +safe_syscall_base: + .cfi_startproc + /* + * The syscall calling convention isn't the same as the C one: + * we enter with o0 == &signal_pending + * o1 == syscall number + * o2 ... o5, (stack) == syscall arguments + * and return the result in x0 + * and the syscall instruction needs + * g1 == syscall number + * o0 ... o5 == syscall arguments + * and returns the result in o0 + * Shuffle everything around appropriately. + */ + mov %o0, %g2 /* signal_pending pointer */ + mov %o1, %g1 /* syscall number */ + mov %o2, %o0 /* syscall arguments */ + mov %o3, %o1 + mov %o4, %o2 + mov %o5, %o3 + ldx [%sp + PARAM(6)], %o4 + ldx [%sp + PARAM(7)], %o5 + + /* + * This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* if signal_pending is non-zero, don't do the call */ + lduw [%g2], %g3 + brnz,pn %g3, 2f + nop + ta 0x6d +safe_syscall_end: + /* code path for having successfully executed the syscall */ + bcs,pn %xcc, 1f + nop + ret + nop + + /* code path when we didn't execute the syscall */ +2: set QEMU_ERESTARTSYS, %o0 + + /* code path setting errno */ +1: mov %o7, %g1 + call safe_syscall_set_errno_tail + mov %g1, %o7 + + .cfi_endproc + .size safe_syscall_base, .-safe_syscall_base diff --git a/common-user/host/x86_64/safe-syscall.inc.S b/common-user/host/x86_64/safe-syscall.inc.S new file mode 100644 index 0000000000..84fed206f9 --- /dev/null +++ b/common-user/host/x86_64/safe-syscall.inc.S @@ -0,0 +1,94 @@ +/* + * safe-syscall.inc.S : host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * This is intended to be included by common-user/safe-syscall.S + * + * Copyright (C) 2015 Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk> + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + + .global safe_syscall_base + .global safe_syscall_start + .global safe_syscall_end + .type safe_syscall_base, @function + + /* This is the entry point for making a system call. The calling + * convention here is that of a C varargs function with the + * first argument an 'int *' to the signal_pending flag, the + * second one the system call number (as a 'long'), and all further + * arguments being syscall arguments (also 'long'). + */ +safe_syscall_base: + .cfi_startproc + /* This saves a frame pointer and aligns the stack for the syscall. + * (It's unclear if the syscall ABI has the same stack alignment + * requirements as the userspace function call ABI, but better safe than + * sorry. Appendix A2 of http://www.x86-64.org/documentation/abi.pdf + * does not list any ABI differences regarding stack alignment.) + */ + push %rbp + .cfi_adjust_cfa_offset 8 + .cfi_rel_offset rbp, 0 + + /* + * The syscall calling convention isn't the same as the C one: + * we enter with rdi == &signal_pending + * rsi == syscall number + * rdx, rcx, r8, r9, (stack), (stack) == syscall arguments + * and return the result in rax + * and the syscall instruction needs + * rax == syscall number + * rdi, rsi, rdx, r10, r8, r9 == syscall arguments + * and returns the result in rax + * Shuffle everything around appropriately. + * Note that syscall will trash rcx and r11. + */ + mov %rsi, %rax /* syscall number */ + mov %rdi, %rbp /* signal_pending pointer */ + /* and the syscall arguments */ + mov %rdx, %rdi + mov %rcx, %rsi + mov %r8, %rdx + mov %r9, %r10 + mov 16(%rsp), %r8 + mov 24(%rsp), %r9 + + /* This next sequence of code works in conjunction with the + * rewind_if_safe_syscall_function(). If a signal is taken + * and the interrupted PC is anywhere between 'safe_syscall_start' + * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. + * The code sequence must therefore be able to cope with this, and + * the syscall instruction must be the final one in the sequence. + */ +safe_syscall_start: + /* if signal_pending is non-zero, don't do the call */ + cmpl $0, (%rbp) + jnz 2f + syscall +safe_syscall_end: + /* code path for having successfully executed the syscall */ + cmp $-4095, %rax + jae 0f + pop %rbp + .cfi_remember_state + .cfi_def_cfa_offset 8 + .cfi_restore rbp + ret + .cfi_restore_state + +0: neg %eax + jmp 1f + + /* code path when we didn't execute the syscall */ +2: mov $QEMU_ERESTARTSYS, %eax + + /* code path setting errno */ +1: pop %rbp + .cfi_def_cfa_offset 8 + .cfi_restore rbp + jmp safe_syscall_set_errno_tail + .cfi_endproc + + .size safe_syscall_base, .-safe_syscall_base diff --git a/common-user/meson.build b/common-user/meson.build new file mode 100644 index 0000000000..5cb42bc664 --- /dev/null +++ b/common-user/meson.build @@ -0,0 +1,6 @@ +common_user_inc += include_directories('host/' / host_arch) + +common_user_ss.add(files( + 'safe-syscall.S', + 'safe-syscall-error.c', +)) diff --git a/common-user/safe-syscall-error.c b/common-user/safe-syscall-error.c new file mode 100644 index 0000000000..cf74b504f8 --- /dev/null +++ b/common-user/safe-syscall-error.c @@ -0,0 +1,25 @@ +/* + * safe-syscall-error.c: errno setting fragment + * This is intended to be invoked by safe-syscall.S + * + * Written by Richard Henderson <rth@twiddle.net> + * Copyright (C) 2021 Red Hat, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "qemu/osdep.h" +#include "user/safe-syscall.h" + +/* + * This is intended to be invoked via tail-call on the error path + * from the assembly in host/arch/safe-syscall.inc.S. This takes + * care of the host specific addressing of errno. + * Return -1 to finalize the return value for safe_syscall_base. + */ +long safe_syscall_set_errno_tail(int value) +{ + errno = value; + return -1; +} diff --git a/common-user/safe-syscall.S b/common-user/safe-syscall.S new file mode 100644 index 0000000000..74f7e35694 --- /dev/null +++ b/common-user/safe-syscall.S @@ -0,0 +1,27 @@ +/* + * safe-syscall.S : include the host-specific assembly fragment + * to handle signals occurring at the same time as system calls. + * + * Written by Peter Maydell <peter.maydell@linaro.org> + * + * Copyright (C) 2016 Linaro Limited + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "special-errno.h" + +/* We have the correct host directory on our include path + * so that this will pull in the right fragment for the architecture. + */ +#include "safe-syscall.inc.S" + +/* We must specifically say that we're happy for the stack to not be + * executable, otherwise the toolchain will default to assuming our + * assembly needs an executable stack and the whole QEMU binary will + * needlessly end up with one. This should be the last thing in this file. + */ +#if defined(__linux__) && defined(__ELF__) +.section .note.GNU-stack, "", %progbits +#endif |