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Unified Diff: sandbox/linux/seccomp-bpf/syscall.cc

Issue 330723003: Clean-up the SandboxSyscall interface (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Address comments. Created 6 years, 6 months ago
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Index: sandbox/linux/seccomp-bpf/syscall.cc
diff --git a/sandbox/linux/seccomp-bpf/syscall.cc b/sandbox/linux/seccomp-bpf/syscall.cc
index fd599e893b2b7d3b3fdefe81dfcfeb8dd17717d4..64c0b8eb9b41b708482571febc4d417b3e1110c4 100644
--- a/sandbox/linux/seccomp-bpf/syscall.cc
+++ b/sandbox/linux/seccomp-bpf/syscall.cc
@@ -11,169 +11,177 @@
namespace sandbox {
- asm( // We need to be able to tell the kernel exactly where we made a
- // system call. The C++ compiler likes to sometimes clone or
- // inline code, which would inadvertently end up duplicating
- // the entry point.
- // "gcc" can suppress code duplication with suitable function
- // attributes, but "clang" doesn't have this ability.
- // The "clang" developer mailing list suggested that the correct
- // and portable solution is a file-scope assembly block.
- // N.B. We do mark our code as a proper function so that backtraces
- // work correctly. But we make absolutely no attempt to use the
- // ABI's calling conventions for passing arguments. We will only
- // ever be called from assembly code and thus can pick more
- // suitable calling conventions.
+namespace {
+
+asm(// We need to be able to tell the kernel exactly where we made a
+ // system call. The C++ compiler likes to sometimes clone or
+ // inline code, which would inadvertently end up duplicating
+ // the entry point.
+ // "gcc" can suppress code duplication with suitable function
+ // attributes, but "clang" doesn't have this ability.
+ // The "clang" developer mailing list suggested that the correct
+ // and portable solution is a file-scope assembly block.
+ // N.B. We do mark our code as a proper function so that backtraces
+ // work correctly. But we make absolutely no attempt to use the
+ // ABI's calling conventions for passing arguments. We will only
+ // ever be called from assembly code and thus can pick more
+ // suitable calling conventions.
#if defined(__i386__)
- ".text\n"
- ".align 16, 0x90\n"
- ".type SyscallAsm, @function\n"
- "SyscallAsm:.cfi_startproc\n"
- // Check if "%eax" is negative. If so, do not attempt to make a
- // system call. Instead, compute the return address that is visible
- // to the kernel after we execute "int $0x80". This address can be
- // used as a marker that BPF code inspects.
- "test %eax, %eax\n"
- "jge 1f\n"
- // Always, make sure that our code is position-independent, or
- // address space randomization might not work on i386. This means,
- // we can't use "lea", but instead have to rely on "call/pop".
- "call 0f; .cfi_adjust_cfa_offset 4\n"
- "0:pop %eax; .cfi_adjust_cfa_offset -4\n"
- "addl $2f-0b, %eax\n"
- "ret\n"
- // Save register that we don't want to clobber. On i386, we need to
- // save relatively aggressively, as there are a couple or registers
- // that are used internally (e.g. %ebx for position-independent
- // code, and %ebp for the frame pointer), and as we need to keep at
- // least a few registers available for the register allocator.
- "1:push %esi; .cfi_adjust_cfa_offset 4\n"
- "push %edi; .cfi_adjust_cfa_offset 4\n"
- "push %ebx; .cfi_adjust_cfa_offset 4\n"
- "push %ebp; .cfi_adjust_cfa_offset 4\n"
- // Copy entries from the array holding the arguments into the
- // correct CPU registers.
- "movl 0(%edi), %ebx\n"
- "movl 4(%edi), %ecx\n"
- "movl 8(%edi), %edx\n"
- "movl 12(%edi), %esi\n"
- "movl 20(%edi), %ebp\n"
- "movl 16(%edi), %edi\n"
- // Enter the kernel.
- "int $0x80\n"
- // This is our "magic" return address that the BPF filter sees.
- "2:"
- // Restore any clobbered registers that we didn't declare to the
- // compiler.
- "pop %ebp; .cfi_adjust_cfa_offset -4\n"
- "pop %ebx; .cfi_adjust_cfa_offset -4\n"
- "pop %edi; .cfi_adjust_cfa_offset -4\n"
- "pop %esi; .cfi_adjust_cfa_offset -4\n"
- "ret\n"
- ".cfi_endproc\n"
- "9:.size SyscallAsm, 9b-SyscallAsm\n"
+ ".text\n"
+ ".align 16, 0x90\n"
+ ".type SyscallAsm, @function\n"
+ "SyscallAsm:.cfi_startproc\n"
+ // Check if "%eax" is negative. If so, do not attempt to make a
+ // system call. Instead, compute the return address that is visible
+ // to the kernel after we execute "int $0x80". This address can be
+ // used as a marker that BPF code inspects.
+ "test %eax, %eax\n"
+ "jge 1f\n"
+ // Always, make sure that our code is position-independent, or
+ // address space randomization might not work on i386. This means,
+ // we can't use "lea", but instead have to rely on "call/pop".
+ "call 0f; .cfi_adjust_cfa_offset 4\n"
+ "0:pop %eax; .cfi_adjust_cfa_offset -4\n"
+ "addl $2f-0b, %eax\n"
+ "ret\n"
+ // Save register that we don't want to clobber. On i386, we need to
+ // save relatively aggressively, as there are a couple or registers
+ // that are used internally (e.g. %ebx for position-independent
+ // code, and %ebp for the frame pointer), and as we need to keep at
+ // least a few registers available for the register allocator.
+ "1:push %esi; .cfi_adjust_cfa_offset 4\n"
+ "push %edi; .cfi_adjust_cfa_offset 4\n"
+ "push %ebx; .cfi_adjust_cfa_offset 4\n"
+ "push %ebp; .cfi_adjust_cfa_offset 4\n"
+ // Copy entries from the array holding the arguments into the
+ // correct CPU registers.
+ "movl 0(%edi), %ebx\n"
+ "movl 4(%edi), %ecx\n"
+ "movl 8(%edi), %edx\n"
+ "movl 12(%edi), %esi\n"
+ "movl 20(%edi), %ebp\n"
+ "movl 16(%edi), %edi\n"
+ // Enter the kernel.
+ "int $0x80\n"
+ // This is our "magic" return address that the BPF filter sees.
+ "2:"
+ // Restore any clobbered registers that we didn't declare to the
+ // compiler.
+ "pop %ebp; .cfi_adjust_cfa_offset -4\n"
+ "pop %ebx; .cfi_adjust_cfa_offset -4\n"
+ "pop %edi; .cfi_adjust_cfa_offset -4\n"
+ "pop %esi; .cfi_adjust_cfa_offset -4\n"
+ "ret\n"
+ ".cfi_endproc\n"
+ "9:.size SyscallAsm, 9b-SyscallAsm\n"
#elif defined(__x86_64__)
- ".text\n"
- ".align 16, 0x90\n"
- ".type SyscallAsm, @function\n"
- "SyscallAsm:.cfi_startproc\n"
- // Check if "%rax" is negative. If so, do not attempt to make a
- // system call. Instead, compute the return address that is visible
- // to the kernel after we execute "syscall". This address can be
- // used as a marker that BPF code inspects.
- "test %rax, %rax\n"
- "jge 1f\n"
- // Always make sure that our code is position-independent, or the
- // linker will throw a hissy fit on x86-64.
- "call 0f; .cfi_adjust_cfa_offset 8\n"
- "0:pop %rax; .cfi_adjust_cfa_offset -8\n"
- "addq $2f-0b, %rax\n"
- "ret\n"
- // We declared all clobbered registers to the compiler. On x86-64,
- // there really isn't much of a problem with register pressure. So,
- // we can go ahead and directly copy the entries from the arguments
- // array into the appropriate CPU registers.
- "1:movq 0(%r12), %rdi\n"
- "movq 8(%r12), %rsi\n"
- "movq 16(%r12), %rdx\n"
- "movq 24(%r12), %r10\n"
- "movq 32(%r12), %r8\n"
- "movq 40(%r12), %r9\n"
- // Enter the kernel.
- "syscall\n"
- // This is our "magic" return address that the BPF filter sees.
- "2:ret\n"
- ".cfi_endproc\n"
- "9:.size SyscallAsm, 9b-SyscallAsm\n"
+ ".text\n"
+ ".align 16, 0x90\n"
+ ".type SyscallAsm, @function\n"
+ "SyscallAsm:.cfi_startproc\n"
+ // Check if "%rax" is negative. If so, do not attempt to make a
+ // system call. Instead, compute the return address that is visible
+ // to the kernel after we execute "syscall". This address can be
+ // used as a marker that BPF code inspects.
+ "test %rax, %rax\n"
+ "jge 1f\n"
+ // Always make sure that our code is position-independent, or the
+ // linker will throw a hissy fit on x86-64.
+ "call 0f; .cfi_adjust_cfa_offset 8\n"
+ "0:pop %rax; .cfi_adjust_cfa_offset -8\n"
+ "addq $2f-0b, %rax\n"
+ "ret\n"
+ // We declared all clobbered registers to the compiler. On x86-64,
+ // there really isn't much of a problem with register pressure. So,
+ // we can go ahead and directly copy the entries from the arguments
+ // array into the appropriate CPU registers.
+ "1:movq 0(%r12), %rdi\n"
+ "movq 8(%r12), %rsi\n"
+ "movq 16(%r12), %rdx\n"
+ "movq 24(%r12), %r10\n"
+ "movq 32(%r12), %r8\n"
+ "movq 40(%r12), %r9\n"
+ // Enter the kernel.
+ "syscall\n"
+ // This is our "magic" return address that the BPF filter sees.
+ "2:ret\n"
+ ".cfi_endproc\n"
+ "9:.size SyscallAsm, 9b-SyscallAsm\n"
#elif defined(__arm__)
- // Throughout this file, we use the same mode (ARM vs. thumb)
- // that the C++ compiler uses. This means, when transfering control
- // from C++ to assembly code, we do not need to switch modes (e.g.
- // by using the "bx" instruction). It also means that our assembly
- // code should not be invoked directly from code that lives in
- // other compilation units, as we don't bother implementing thumb
- // interworking. That's OK, as we don't make any of the assembly
- // symbols public. They are all local to this file.
- ".text\n"
- ".align 2\n"
- ".type SyscallAsm, %function\n"
+ // Throughout this file, we use the same mode (ARM vs. thumb)
+ // that the C++ compiler uses. This means, when transfering control
+ // from C++ to assembly code, we do not need to switch modes (e.g.
+ // by using the "bx" instruction). It also means that our assembly
+ // code should not be invoked directly from code that lives in
+ // other compilation units, as we don't bother implementing thumb
+ // interworking. That's OK, as we don't make any of the assembly
+ // symbols public. They are all local to this file.
+ ".text\n"
+ ".align 2\n"
+ ".type SyscallAsm, %function\n"
#if defined(__thumb__)
- ".thumb_func\n"
+ ".thumb_func\n"
#else
- ".arm\n"
+ ".arm\n"
#endif
- "SyscallAsm:.fnstart\n"
- "@ args = 0, pretend = 0, frame = 8\n"
- "@ frame_needed = 1, uses_anonymous_args = 0\n"
+ "SyscallAsm:.fnstart\n"
+ "@ args = 0, pretend = 0, frame = 8\n"
+ "@ frame_needed = 1, uses_anonymous_args = 0\n"
#if defined(__thumb__)
- ".cfi_startproc\n"
- "push {r7, lr}\n"
- ".cfi_offset 14, -4\n"
- ".cfi_offset 7, -8\n"
- "mov r7, sp\n"
- ".cfi_def_cfa_register 7\n"
- ".cfi_def_cfa_offset 8\n"
+ ".cfi_startproc\n"
+ "push {r7, lr}\n"
+ ".cfi_offset 14, -4\n"
+ ".cfi_offset 7, -8\n"
+ "mov r7, sp\n"
+ ".cfi_def_cfa_register 7\n"
+ ".cfi_def_cfa_offset 8\n"
#else
- "stmfd sp!, {fp, lr}\n"
- "add fp, sp, #4\n"
+ "stmfd sp!, {fp, lr}\n"
+ "add fp, sp, #4\n"
#endif
- // Check if "r0" is negative. If so, do not attempt to make a
- // system call. Instead, compute the return address that is visible
- // to the kernel after we execute "swi 0". This address can be
- // used as a marker that BPF code inspects.
- "cmp r0, #0\n"
- "bge 1f\n"
- "adr r0, 2f\n"
- "b 2f\n"
- // We declared (almost) all clobbered registers to the compiler. On
- // ARM there is no particular register pressure. So, we can go
- // ahead and directly copy the entries from the arguments array
- // into the appropriate CPU registers.
- "1:ldr r5, [r6, #20]\n"
- "ldr r4, [r6, #16]\n"
- "ldr r3, [r6, #12]\n"
- "ldr r2, [r6, #8]\n"
- "ldr r1, [r6, #4]\n"
- "mov r7, r0\n"
- "ldr r0, [r6, #0]\n"
- // Enter the kernel
- "swi 0\n"
- // Restore the frame pointer. Also restore the program counter from
- // the link register; this makes us return to the caller.
+ // Check if "r0" is negative. If so, do not attempt to make a
+ // system call. Instead, compute the return address that is visible
+ // to the kernel after we execute "swi 0". This address can be
+ // used as a marker that BPF code inspects.
+ "cmp r0, #0\n"
+ "bge 1f\n"
+ "adr r0, 2f\n"
+ "b 2f\n"
+ // We declared (almost) all clobbered registers to the compiler. On
+ // ARM there is no particular register pressure. So, we can go
+ // ahead and directly copy the entries from the arguments array
+ // into the appropriate CPU registers.
+ "1:ldr r5, [r6, #20]\n"
+ "ldr r4, [r6, #16]\n"
+ "ldr r3, [r6, #12]\n"
+ "ldr r2, [r6, #8]\n"
+ "ldr r1, [r6, #4]\n"
+ "mov r7, r0\n"
+ "ldr r0, [r6, #0]\n"
+ // Enter the kernel
+ "swi 0\n"
+// Restore the frame pointer. Also restore the program counter from
+// the link register; this makes us return to the caller.
#if defined(__thumb__)
- "2:pop {r7, pc}\n"
- ".cfi_endproc\n"
+ "2:pop {r7, pc}\n"
+ ".cfi_endproc\n"
#else
- "2:ldmfd sp!, {fp, pc}\n"
+ "2:ldmfd sp!, {fp, pc}\n"
#endif
- ".fnend\n"
- "9:.size SyscallAsm, 9b-SyscallAsm\n"
+ ".fnend\n"
+ "9:.size SyscallAsm, 9b-SyscallAsm\n"
#endif
- ); // asm
+ ); // asm
+
+} // namespace
-intptr_t SandboxSyscall(int nr,
- intptr_t p0, intptr_t p1, intptr_t p2,
- intptr_t p3, intptr_t p4, intptr_t p5) {
+intptr_t Syscall::Call(int nr,
+ intptr_t p0,
+ intptr_t p1,
+ intptr_t p2,
+ intptr_t p3,
+ intptr_t p4,
+ intptr_t p5) {
// We rely on "intptr_t" to be the exact size as a "void *". This is
// typically true, but just in case, we add a check. The language
// specification allows platforms some leeway in cases, where
@@ -181,61 +189,78 @@ intptr_t SandboxSyscall(int nr,
// that this would only be an issue for IA64, which we are currently not
// planning on supporting. And it is even possible that this would work
// on IA64, but for lack of actual hardware, I cannot test.
- COMPILE_ASSERT(sizeof(void *) == sizeof(intptr_t),
+ COMPILE_ASSERT(sizeof(void*) == sizeof(intptr_t),
pointer_types_and_intptr_must_be_exactly_the_same_size);
- const intptr_t args[6] = { p0, p1, p2, p3, p4, p5 };
+ const intptr_t args[6] = {p0, p1, p2, p3, p4, p5};
- // Invoke our file-scope assembly code. The constraints have been picked
- // carefully to match what the rest of the assembly code expects in input,
- // output, and clobbered registers.
+// Invoke our file-scope assembly code. The constraints have been picked
+// carefully to match what the rest of the assembly code expects in input,
+// output, and clobbered registers.
#if defined(__i386__)
intptr_t ret = nr;
asm volatile(
- "call SyscallAsm\n"
- // N.B. These are not the calling conventions normally used by the ABI.
- : "=a"(ret)
- : "0"(ret), "D"(args)
- : "cc", "esp", "memory", "ecx", "edx");
+ "call SyscallAsm\n"
+ // N.B. These are not the calling conventions normally used by the ABI.
+ : "=a"(ret)
+ : "0"(ret), "D"(args)
+ : "cc", "esp", "memory", "ecx", "edx");
#elif defined(__x86_64__)
intptr_t ret = nr;
{
- register const intptr_t *data __asm__("r12") = args;
+ register const intptr_t* data __asm__("r12") = args;
asm volatile(
- "lea -128(%%rsp), %%rsp\n" // Avoid red zone.
- "call SyscallAsm\n"
- "lea 128(%%rsp), %%rsp\n"
- // N.B. These are not the calling conventions normally used by the ABI.
- : "=a"(ret)
- : "0"(ret), "r"(data)
- : "cc", "rsp", "memory",
- "rcx", "rdi", "rsi", "rdx", "r8", "r9", "r10", "r11");
+ "lea -128(%%rsp), %%rsp\n" // Avoid red zone.
+ "call SyscallAsm\n"
+ "lea 128(%%rsp), %%rsp\n"
+ // N.B. These are not the calling conventions normally used by the ABI.
+ : "=a"(ret)
+ : "0"(ret), "r"(data)
+ : "cc",
+ "rsp",
+ "memory",
+ "rcx",
+ "rdi",
+ "rsi",
+ "rdx",
+ "r8",
+ "r9",
+ "r10",
+ "r11");
}
#elif defined(__arm__)
intptr_t ret;
{
register intptr_t inout __asm__("r0") = nr;
- register const intptr_t *data __asm__("r6") = args;
+ register const intptr_t* data __asm__("r6") = args;
asm volatile(
- "bl SyscallAsm\n"
- // N.B. These are not the calling conventions normally used by the ABI.
- : "=r"(inout)
- : "0"(inout), "r"(data)
- : "cc", "lr", "memory", "r1", "r2", "r3", "r4", "r5"
+ "bl SyscallAsm\n"
+ // N.B. These are not the calling conventions normally used by the ABI.
+ : "=r"(inout)
+ : "0"(inout), "r"(data)
+ : "cc",
+ "lr",
+ "memory",
+ "r1",
+ "r2",
+ "r3",
+ "r4",
+ "r5"
#if !defined(__thumb__)
- // In thumb mode, we cannot use "r7" as a general purpose register, as
- // it is our frame pointer. We have to manually manage and preserve it.
- // In ARM mode, we have a dedicated frame pointer register and "r7" is
- // thus available as a general purpose register. We don't preserve it,
- // but instead mark it as clobbered.
- , "r7"
+ // In thumb mode, we cannot use "r7" as a general purpose register, as
+ // it is our frame pointer. We have to manually manage and preserve
+ // it.
+ // In ARM mode, we have a dedicated frame pointer register and "r7" is
+ // thus available as a general purpose register. We don't preserve it,
+ // but instead mark it as clobbered.
+ ,
+ "r7"
#endif // !defined(__thumb__)
- );
+ );
ret = inout;
}
#else
- errno = ENOSYS;
- intptr_t ret = -1;
+#error "Unimplemented architecture"
#endif
return ret;
}
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