diff options
Diffstat (limited to 'man2/syscall.2')
| -rw-r--r-- | man2/syscall.2 | 38 |
1 files changed, 19 insertions, 19 deletions
diff --git a/man2/syscall.2 b/man2/syscall.2 index 43f054a..01229e8 100644 --- a/man2/syscall.2 +++ b/man2/syscall.2 @@ -12,7 +12,7 @@ .\" 2015-01-17, Kees Cook <keescook@chromium.org> .\" Added mips and arm64. .\" -.TH syscall 2 2023-05-03 "Linux man-pages 6.05.01" +.TH syscall 2 2023-10-31 "Linux man-pages 6.7" .SH NAME syscall \- indirect system call .SH LIBRARY @@ -22,15 +22,15 @@ Standard C library .nf .BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */" .B #include <unistd.h> -.PP +.P .BI "long syscall(long " number ", ...);" .fi -.PP +.P .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE -.PP +.P .BR syscall (): .nf Since glibc 2.19: @@ -49,13 +49,13 @@ Employing .BR syscall () is useful, for example, when invoking a system call that has no wrapper function in the C library. -.PP +.P .BR syscall () saves CPU registers before making the system call, restores the registers upon return from the system call, and stores any error returned by the system call in .BR errno (3). -.PP +.P Symbolic constants for system call numbers can be found in the header file .IR <sys/syscall.h> . .SH RETURN VALUE @@ -68,7 +68,7 @@ and an error number is stored in .TP .B ENOSYS The requested system call number is not implemented. -.PP +.P Other errors are specific to the invoked system call. .SH NOTES .BR syscall () @@ -85,7 +85,7 @@ However, when using to make a system call, the caller might need to handle architecture-dependent details; this requirement is most commonly encountered on certain 32-bit architectures. -.PP +.P For example, on the ARM architecture Embedded ABI (EABI), a 64-bit value (e.g., .IR "long long" ) @@ -97,7 +97,7 @@ the .BR readahead (2) system call would be invoked as follows on the ARM architecture with the EABI in little endian mode: -.PP +.P .in +4n .EX syscall(SYS_readahead, fd, 0, @@ -106,7 +106,7 @@ syscall(SYS_readahead, fd, 0, count); .EE .in -.PP +.P Since the offset argument is 64 bits, and the first argument .RI ( fd ) is passed in @@ -120,16 +120,16 @@ That means inserting a dummy value into (the second argument of 0). Care also must be taken so that the split follows endian conventions (according to the C ABI for the platform). -.PP +.P Similar issues can occur on MIPS with the O32 ABI, on PowerPC and parisc with the 32-bit ABI, and on Xtensa. .\" Mike Frysinger: this issue ends up forcing MIPS .\" O32 to take 7 arguments to syscall() -.PP +.P .\" See arch/parisc/kernel/sys_parisc.c. Note that while the parisc C ABI also uses aligned register pairs, it uses a shim layer to hide the issue from user space. -.PP +.P The affected system calls are .BR fadvise64_64 (2), .BR ftruncate64 (2), @@ -140,7 +140,7 @@ The affected system calls are .BR sync_file_range (2), and .BR truncate64 (2). -.PP +.P .\" You need to look up the syscalls directly in the kernel source to see if .\" they should be in this list. For example, look at fs/read_write.c and .\" the function signatures that do: @@ -159,7 +159,7 @@ Welcome to the wonderful world of historical baggage. Every architecture has its own way of invoking and passing arguments to the kernel. The details for various architectures are listed in the two tables below. -.PP +.P The first table lists the instruction used to transition to kernel mode (which might not be the fastest or best way to transition to the kernel, so you might have to refer to @@ -202,7 +202,7 @@ x86-64 syscall rax rax rdx - 5 x32 syscall rax rax rdx - 5 xtensa syscall a2 a2 - - .TE -.PP +.P Notes: .IP \[bu] 3 On a few architectures, @@ -292,7 +292,7 @@ in the system call interface, even if it is defined in the System V ABI. .in .ft P \} -.PP +.P The second table shows the registers used to pass the system call arguments. .if t \{\ .ft CW @@ -329,7 +329,7 @@ x86-64 rdi rsi rdx r10 r8 r9 - x32 rdi rsi rdx r10 r8 r9 - xtensa a6 a3 a4 a5 a8 a9 - .TE -.PP +.P Notes: .IP \[bu] 3 The mips/o32 system call convention passes @@ -338,7 +338,7 @@ arguments 5 through 8 on the user stack. .in .ft P \} -.PP +.P Note that these tables don't cover the entire calling convention\[em]some architectures may indiscriminately clobber other registers not listed here. .SH EXAMPLES |