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[PULL 02/15] linux-user: Move syscall error detection into safe_syscall_
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From: |
Richard Henderson |
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Subject: |
[PULL 02/15] linux-user: Move syscall error detection into safe_syscall_base |
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Date: |
Mon, 20 Dec 2021 12:24:47 -0800 |
The current api from safe_syscall_base() is to return -errno, which is
the interface provided by *some* linux kernel abis. The wrapper macro,
safe_syscall(), detects error, stores into errno, and returns -1, to
match the api of the system syscall().
For those kernel abis that do not return -errno natively, this leads
to double syscall error detection. E.g. Linux ppc64, which sets the
SO flag for error.
Simplify the usage from C by moving the error detection into assembly,
and usage from assembly by providing a C helper with which to set errno.
Reviewed-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
linux-user/safe-syscall.h | 16 +++-------
linux-user/safe-syscall-error.c | 28 ++++++++++++++++
linux-user/host/aarch64/safe-syscall.inc.S | 20 ++++++------
linux-user/host/arm/safe-syscall.inc.S | 27 ++++++++++------
linux-user/host/i386/safe-syscall.inc.S | 37 +++++++++++++++-------
linux-user/host/ppc64/safe-syscall.inc.S | 24 +++++++-------
linux-user/host/riscv/safe-syscall.inc.S | 20 ++++++------
linux-user/host/s390x/safe-syscall.inc.S | 32 ++++++++++++-------
linux-user/host/x86_64/safe-syscall.inc.S | 29 +++++++++--------
linux-user/meson.build | 1 +
10 files changed, 147 insertions(+), 87 deletions(-)
create mode 100644 linux-user/safe-syscall-error.c
diff --git a/linux-user/safe-syscall.h b/linux-user/safe-syscall.h
index aaa9ffc0e2..97837faddb 100644
--- a/linux-user/safe-syscall.h
+++ b/linux-user/safe-syscall.h
@@ -127,21 +127,15 @@
#ifdef HAVE_SAFE_SYSCALL
/* The core part of this function is implemented in assembly */
extern long safe_syscall_base(int *pending, long number, ...);
+extern long safe_syscall_set_errno_tail(int value);
+
/* These are defined by the safe-syscall.inc.S file */
extern char safe_syscall_start[];
extern char safe_syscall_end[];
-#define safe_syscall(...) \
- ({ \
- long ret_; \
- int *psp_ = &((TaskState *)thread_cpu->opaque)->signal_pending; \
- ret_ = safe_syscall_base(psp_, __VA_ARGS__); \
- if (is_error(ret_)) { \
- errno = -ret_; \
- ret_ = -1; \
- } \
- ret_; \
- })
+#define safe_syscall(...) \
+ safe_syscall_base(&((TaskState *)thread_cpu->opaque)->signal_pending, \
+ __VA_ARGS__)
#else
diff --git a/linux-user/safe-syscall-error.c b/linux-user/safe-syscall-error.c
new file mode 100644
index 0000000000..d7e2700f81
--- /dev/null
+++ b/linux-user/safe-syscall-error.c
@@ -0,0 +1,28 @@
+/*
+ * 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 "hostdep.h"
+#include "safe-syscall.h"
+
+#ifdef HAVE_SAFE_SYSCALL
+/*
+ * 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;
+}
+#endif
diff --git a/linux-user/host/aarch64/safe-syscall.inc.S
b/linux-user/host/aarch64/safe-syscall.inc.S
index e2e726ef55..76a0a18a6c 100644
--- a/linux-user/host/aarch64/safe-syscall.inc.S
+++ b/linux-user/host/aarch64/safe-syscall.inc.S
@@ -22,15 +22,12 @@
* 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').
- * We return a long which is the syscall's return value, which
- * may be negative-errno on failure. Conversion to the
- * -1-and-errno-set convention is done by the calling wrapper.
*/
safe_syscall_base:
.cfi_startproc
/* The syscall calling convention isn't the same as the
* C one:
- * we enter with x0 == *signal_pending
+ * we enter with x0 == &signal_pending
* x1 == syscall number
* x2 ... x7, (stack) == syscall arguments
* and return the result in x0
@@ -60,16 +57,21 @@ safe_syscall_base:
safe_syscall_start:
/* if signal_pending is non-zero, don't do the call */
ldr w10, [x9]
- cbnz w10, 0f
+ cbnz w10, 2f
svc 0x0
safe_syscall_end:
/* code path for having successfully executed the syscall */
+ cmp x0, #-4096
+ b.hi 0f
ret
-0:
+ /* code path setting errno */
+0: neg w0, w0
+ b safe_syscall_set_errno_tail
+
/* code path when we didn't execute the syscall */
- mov x0, #-TARGET_ERESTARTSYS
- ret
- .cfi_endproc
+2: mov w0, #TARGET_ERESTARTSYS
+ b safe_syscall_set_errno_tail
+ .cfi_endproc
.size safe_syscall_base, .-safe_syscall_base
diff --git a/linux-user/host/arm/safe-syscall.inc.S
b/linux-user/host/arm/safe-syscall.inc.S
index 1f1ee8327b..618112c6bf 100644
--- a/linux-user/host/arm/safe-syscall.inc.S
+++ b/linux-user/host/arm/safe-syscall.inc.S
@@ -27,9 +27,6 @@
* 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').
- * We return a long which is the syscall's return value, which
- * may be negative-errno on failure. Conversion to the
- * -1-and-errno-set convention is done by the calling wrapper.
*/
safe_syscall_base:
.fnstart
@@ -46,7 +43,7 @@ safe_syscall_base:
.cfi_rel_offset lr, 20
/* The syscall calling convention isn't the same as the C one:
- * we enter with r0 == *signal_pending
+ * we enter with r0 == &signal_pending
* r1 == syscall number
* r2, r3, [sp+0] ... [sp+12] == syscall arguments
* and return the result in r0
@@ -74,17 +71,29 @@ safe_syscall_start:
/* if signal_pending is non-zero, don't do the call */
ldr r12, [r8] /* signal_pending */
tst r12, r12
- bne 1f
+ 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 }
-1:
/* code path when we didn't execute the syscall */
- ldr r0, =-TARGET_ERESTARTSYS
- pop { r4, r5, r6, r7, r8, pc }
+2: mov r0, #TARGET_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/linux-user/host/i386/safe-syscall.inc.S
b/linux-user/host/i386/safe-syscall.inc.S
index e425aa54d8..f5883234bb 100644
--- a/linux-user/host/i386/safe-syscall.inc.S
+++ b/linux-user/host/i386/safe-syscall.inc.S
@@ -20,9 +20,6 @@
* 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').
- * We return a long which is the syscall's return value, which
- * may be negative-errno on failure. Conversion to the
- * -1-and-errno-set convention is done by the calling wrapper.
*/
safe_syscall_base:
.cfi_startproc
@@ -41,7 +38,7 @@ safe_syscall_base:
/* The syscall calling convention isn't the same as the C one:
* we enter with 0(%esp) == return address
- * 4(%esp) == *signal_pending
+ * 4(%esp) == &signal_pending
* 8(%esp) == syscall number
* 12(%esp) ... 32(%esp) == syscall arguments
* and return the result in eax
@@ -70,11 +67,13 @@ 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 1f
+ 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
@@ -89,12 +88,28 @@ safe_syscall_end:
.cfi_adjust_cfa_offset -4
.cfi_restore ebp
ret
-
-1:
- /* code path when we didn't execute the syscall */
.cfi_restore_state
- mov $-TARGET_ERESTARTSYS, %eax
- jmp safe_syscall_end
- .cfi_endproc
+0: neg %eax
+ jmp 1f
+
+ /* code path when we didn't execute the syscall */
+2: mov $TARGET_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/linux-user/host/ppc64/safe-syscall.inc.S
b/linux-user/host/ppc64/safe-syscall.inc.S
index 4b57440585..3a640cfc04 100644
--- a/linux-user/host/ppc64/safe-syscall.inc.S
+++ b/linux-user/host/ppc64/safe-syscall.inc.S
@@ -22,9 +22,6 @@
* 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').
- * We return a long which is the syscall's return value, which
- * may be negative-errno on failure. Conversion to the
- * -1-and-errno-set convention is done by the calling wrapper.
*/
#if _CALL_ELF == 2
safe_syscall_base:
@@ -39,7 +36,7 @@ safe_syscall_base:
.L.safe_syscall_base:
.cfi_startproc
#endif
- /* We enter with r3 == *signal_pending
+ /* We enter with r3 == &signal_pending
* r4 == syscall number
* r5 ... r10 == syscall arguments
* and return the result in r3
@@ -71,21 +68,22 @@ safe_syscall_start:
/* if signal_pending is non-zero, don't do the call */
lwz 12, 0(14)
cmpwi 0, 12, 0
- bne- 0f
+ bne- 2f
sc
safe_syscall_end:
/* code path when we did execute the syscall */
- ld 14, 16(1) /* restore r14 to its original value */
- bnslr+
-
- /* syscall failed; return negative errno */
- neg 3, 3
+ ld 14, 16(1) /* restore r14 */
+ bso- 1f
blr
/* code path when we didn't execute the syscall */
-0: addi 3, 0, -TARGET_ERESTARTSYS
- ld 14, 16(1) /* restore r14 to its original value */
- blr
+2: ld 14, 16(1) /* restore r14 */
+ addi 3, 0, TARGET_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
diff --git a/linux-user/host/riscv/safe-syscall.inc.S
b/linux-user/host/riscv/safe-syscall.inc.S
index 95c4832de2..54c2e23f75 100644
--- a/linux-user/host/riscv/safe-syscall.inc.S
+++ b/linux-user/host/riscv/safe-syscall.inc.S
@@ -23,15 +23,12 @@
* 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').
- * We return a long which is the syscall's return value, which
- * may be negative-errno on failure. Conversion to the
- * -1-and-errno-set convention is done by the calling wrapper.
*/
safe_syscall_base:
.cfi_startproc
/*
* The syscall calling convention is nearly the same as C:
- * we enter with a0 == *signal_pending
+ * we enter with a0 == &signal_pending
* a1 == syscall number
* a2 ... a7 == syscall arguments
* and return the result in a0
@@ -62,16 +59,21 @@ safe_syscall_base:
safe_syscall_start:
/* If signal_pending is non-zero, don't do the call */
lw t1, 0(t0)
- bnez t1, 0f
+ bnez t1, 2f
scall
safe_syscall_end:
/* code path for having successfully executed the syscall */
+ li t2, -4096
+ bgtu a0, t2, 0f
ret
-0:
+ /* code path setting errno */
+0: neg a0, a0
+ j safe_syscall_set_errno_tail
+
/* code path when we didn't execute the syscall */
- li a0, -TARGET_ERESTARTSYS
- ret
- .cfi_endproc
+2: li a0, TARGET_ERESTARTSYS
+ j safe_syscall_set_errno_tail
+ .cfi_endproc
.size safe_syscall_base, .-safe_syscall_base
diff --git a/linux-user/host/s390x/safe-syscall.inc.S
b/linux-user/host/s390x/safe-syscall.inc.S
index d97d27458e..899dab39e9 100644
--- a/linux-user/host/s390x/safe-syscall.inc.S
+++ b/linux-user/host/s390x/safe-syscall.inc.S
@@ -20,9 +20,6 @@
* 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').
- * We return a long which is the syscall's return value, which
- * may be negative-errno on failure. Conversion to the
- * -1-and-errno-set convention is done by the calling wrapper.
*/
safe_syscall_base:
.cfi_startproc
@@ -44,9 +41,9 @@ safe_syscall_base:
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
+ /*
+ * 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
@@ -77,14 +74,25 @@ safe_syscall_start:
svc 0
safe_syscall_end:
-1: lg %r15,0(%r15) /* load back chain */
+ /* 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 */
- br %r14
- .cfi_restore_state
-2: lghi %r2, -TARGET_ERESTARTSYS
- j 1b
- .cfi_endproc
+ 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, TARGET_ERESTARTSYS
+ jg safe_syscall_set_errno_tail
+
+ .cfi_endproc
.size safe_syscall_base, .-safe_syscall_base
diff --git a/linux-user/host/x86_64/safe-syscall.inc.S
b/linux-user/host/x86_64/safe-syscall.inc.S
index 158225553e..39b64250c3 100644
--- a/linux-user/host/x86_64/safe-syscall.inc.S
+++ b/linux-user/host/x86_64/safe-syscall.inc.S
@@ -19,9 +19,6 @@
* 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').
- * We return a long which is the syscall's return value, which
- * may be negative-errno on failure. Conversion to the
- * -1-and-errno-set convention is done by the calling wrapper.
*/
safe_syscall_base:
.cfi_startproc
@@ -35,9 +32,9 @@ safe_syscall_base:
.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
+ /*
+ * 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
@@ -68,24 +65,30 @@ safe_syscall_base:
safe_syscall_start:
/* if signal_pending is non-zero, don't do the call */
cmpl $0, (%rbp)
- jnz 1f
+ 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
-
-1:
- /* code path when we didn't execute the syscall */
.cfi_restore_state
- mov $-TARGET_ERESTARTSYS, %rax
- pop %rbp
+
+0: neg %eax
+ jmp 1f
+
+ /* code path when we didn't execute the syscall */
+2: mov $TARGET_ERESTARTSYS, %eax
+
+ /* code path setting errno */
+1: pop %rbp
.cfi_def_cfa_offset 8
.cfi_restore rbp
- ret
+ jmp safe_syscall_set_errno_tail
.cfi_endproc
.size safe_syscall_base, .-safe_syscall_base
diff --git a/linux-user/meson.build b/linux-user/meson.build
index bf62c13e37..94ac3c58ce 100644
--- a/linux-user/meson.build
+++ b/linux-user/meson.build
@@ -10,6 +10,7 @@ linux_user_ss.add(files(
'main.c',
'mmap.c',
'safe-syscall.S',
+ 'safe-syscall-error.c',
'signal.c',
'strace.c',
'syscall.c',
--
2.25.1
- [PULL 00/15] *-user: simplify safe signal handling, Richard Henderson, 2021/12/20
- [PULL 04/15] linux-user/host/sparc64: Add safe-syscall.inc.S, Richard Henderson, 2021/12/20
- [PULL 02/15] linux-user: Move syscall error detection into safe_syscall_base,
Richard Henderson <=
- [PULL 01/15] linux-user: Untabify all safe-syscall.inc.S, Richard Henderson, 2021/12/20
- [PULL 10/15] bsd-user: Create special-errno.h, Richard Henderson, 2021/12/20
- [PULL 14/15] meson: Move linux_user_ss to linux-user/, Richard Henderson, 2021/12/20
- [PULL 07/15] bsd-user: Rename TARGET_ERESTARTSYS to QEMU_ERESTARTSYS, Richard Henderson, 2021/12/20
- [PULL 03/15] linux-user/host/mips: Add safe-syscall.inc.S, Richard Henderson, 2021/12/20
- [PULL 12/15] common-user: Adjust system call return on FreeBSD, Richard Henderson, 2021/12/20
- [PULL 05/15] linux-user: Remove HAVE_SAFE_SYSCALL and hostdep.h, Richard Henderson, 2021/12/20
- [PULL 09/15] linux-user: Create special-errno.h, Richard Henderson, 2021/12/20
- [PULL 15/15] meson: Move bsd_user_ss to bsd-user/, Richard Henderson, 2021/12/20
- [PULL 08/15] linux-user: Rename TARGET_QEMU_ESIGRETURN to QEMU_ESIGRETURN, Richard Henderson, 2021/12/20