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[37.14.164.149]) by smtp.gmail.com with ESMTPSA id n13sm13054883wrt.44.2021.11.23.09.38.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Nov 2021 09:38:07 -0800 (PST) From: Richard Henderson To: qemu-devel@nongnu.org Subject: [PATCH v6 03/16] linux-user: Move syscall error detection into safe_syscall_base Date: Tue, 23 Nov 2021 18:37:46 +0100 Message-Id: <20211123173759.1383510-4-richard.henderson@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211123173759.1383510-1-richard.henderson@linaro.org> References: <20211123173759.1383510-1-richard.henderson@linaro.org> MIME-Version: 1.0 X-Host-Lookup-Failed: Reverse DNS lookup failed for 2a00:1450:4864:20::42a (failed) Received-SPF: pass client-ip=2a00:1450:4864:20::42a; envelope-from=richard.henderson@linaro.org; helo=mail-wr1-x42a.google.com X-Spam_score_int: -12 X-Spam_score: -1.3 X-Spam_bar: - X-Spam_report: (-1.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, PDS_HP_HELO_NORDNS=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: laurent@vivier.eu, imp@bsdimp.com Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" 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. Signed-off-by: Richard Henderson Reviewed-by: Warner Losh --- 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 | 20 ++++++------ 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, 145 insertions(+), 85 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 + * 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 5f19cd193c..b370889480 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 @@ -69,19 +66,20 @@ safe_syscall_start: /* if signal_pending is non-zero, don't do the call */ lwz 12, 0(11) cmpwi 0, 12, 0 - bne- 0f + bne- 2f sc safe_syscall_end: /* code path when we did execute the syscall */ - bnslr+ - - /* syscall failed; return negative errno */ - neg 3, 3 + bso- 1f blr /* code path when we didn't execute the syscall */ -0: addi 3, 0, -TARGET_ERESTARTSYS - blr +2: 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',