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The return type of syscall() is long so __syscall_error, which is jumped
to by syscall handlers to stash an error number into errno, must return
long too otherwhise it returs 4294967295L instead of -1L. For example,
syscall for x86_64 is defined in libc/sysdeps/linux/x86_64/syscall.S as
syscall:
movq %rdi, %rax /* Syscall number -> rax. */
movq %rsi, %rdi /* shift arg1 - arg5. */
movq %rdx, %rsi
movq %rcx, %rdx
movq %r8, %r10
movq %r9, %r8
movq 8(%rsp),%r9 /* arg6 is on the stack. */
syscall /* Do the system call. */
cmpq $-4095, %rax /* Check %rax for error. */
jae __syscall_error /* Branch forward if it failed. */
ret /* Return to caller. */
In libc/sysdeps/linux/x86_64/__syscall_error.c, __syscall_error is
defined as
int __syscall_error(void) attribute_hidden;
int __syscall_error(void)
{
register int err_no __asm__ ("%rcx");
__asm__ ("mov %rax, %rcx\n\t"
"neg %rcx");
__set_errno(err_no);
return -1;
}
So __syscall_error returns -1 as a 32-bit int in a 64-bit register, %rax
(0x00000000ffffffff, whose decimal value is decimal 4294967295) and a
test like this always returns false:
if (syscall(number, ...) == -1)
foo();
Fix the error by making __syscall_error return a long, like syscall().
The problem can be circumvented by the caller by coercing the returned
value to int before comparing it to -1:
if ((int) syscall(number, ...) == -1)
foo();
The same problem probably occurs on other 64-bit systems but so far only
x86_64 was tested, so this change must be considered experimental.
Signed-off-by: Carlos Santos <unixmania@gmail.com>
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This matches a similar change made to glibc.
No functional changes here.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
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Here are a number of minor changes to FR-V-specific bits of the uClibc
port:
- I've adjusted the definition of _dl_mmap to cope with the fact that
there will be a definition for an mmap2-only system.
- We don't have COPY relocs, so optimize the copy reloc-related code
away.
- Change the page size to 16KiB, to match the ABI spec, and not a
stale value I'd copied from a linker config file. Oops.
- Fix error handling in clone and vfork; parts of the changes by David
Howells <dhowells@redhat.com>
- Rearrange includes in crtreloc.c.
- Change the API of __syscall_error, to reduce code size.
- Improve __syscall_return in terms of code size, so as to enable
tail-calling of __syscall_error, at least within libc. Ideally,
__syscall_error should be hidden within libc.so, but this didn't
work because of libdl. I haven't looked into why, and figured I'd
leave it visible for now.
- Rename enumerators and macros in sys/ucontext.h to reduce namespace
pollution.
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This patch adds code to uClibc to support a new ABI designed for the
FR-V architecture, that enables text segments of executables and
shared libraries to be shared by multiple processes on an OS such as
uClinux, that can run on FR-V processors without an MMU.
Patches for binutils and GCC have just been posted in the
corresponding mailing lists. The binutils patch was approved,
but there's one additional patch pending review, that I posted
this week. An updated GCC patch will be posted to
gcc-patches@gcc.gnu.org as soon as I complete testing (I used a
known-good compiler to test the uClibc patch below).
Since the existing dynamic loader code didn't support independent
relocation of segments, it required changes that were somewhat
extensive. I've added a number of new machine-specific macros to try
to keep the platform and ABI-specific details outside the generic
code. I hope this is not a problem.
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