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* [newlib-cygwin] Only pass the minimum number of syscall arguments
@ 2020-02-11 8:42 Corinna Vinschen
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From: Corinna Vinschen @ 2020-02-11 8:42 UTC (permalink / raw)
To: newlib-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=9b51beeb2af79d2d492e59c853ebabd4560c225a
commit 9b51beeb2af79d2d492e59c853ebabd4560c225a
Author: Georg Sauthoff <mail@gms.tf>
Date: Mon Feb 10 21:19:58 2020 +0100
Only pass the minimum number of syscall arguments
Previously, __internal_syscall() compiled into asm-code that unconditionally
sets the syscall argument registers a0 to a5.
For example, the instruction sequence for a exit syscall looked like
this:
li a0, 1 # in ther caller of exit()
# ... # in newlib:
li a1, 0 # unused arguments
li a2, 0
li a3, 0
li a4, 0
li a5, 0
li a7, 93 # exit syscall number
(i.e. the binary contains then 5 superfluous instructions for this
one argument syscall)
This commit changes the RISC-V syscall code such that only the required
syscall argument registers are set.
GCC detects that argc is known at compile time and thus evaluates all the
if-statements where argc is used at compile time (tested with -O2 and -Os).
Diff:
---
libgloss/riscv/internal_syscall.h | 41 ++++++++++++++++++++++++++++-----------
libgloss/riscv/sys_access.c | 2 +-
libgloss/riscv/sys_close.c | 2 +-
libgloss/riscv/sys_exit.c | 2 +-
libgloss/riscv/sys_faccessat.c | 2 +-
libgloss/riscv/sys_fstat.c | 2 +-
libgloss/riscv/sys_fstatat.c | 2 +-
libgloss/riscv/sys_gettimeofday.c | 2 +-
libgloss/riscv/sys_link.c | 2 +-
libgloss/riscv/sys_lseek.c | 2 +-
libgloss/riscv/sys_lstat.c | 2 +-
libgloss/riscv/sys_open.c | 2 +-
libgloss/riscv/sys_openat.c | 2 +-
libgloss/riscv/sys_read.c | 2 +-
libgloss/riscv/sys_sbrk.c | 4 ++--
libgloss/riscv/sys_stat.c | 2 +-
libgloss/riscv/sys_unlink.c | 2 +-
libgloss/riscv/sys_write.c | 2 +-
18 files changed, 48 insertions(+), 29 deletions(-)
diff --git a/libgloss/riscv/internal_syscall.h b/libgloss/riscv/internal_syscall.h
index e5d5594..1f1f42f 100644
--- a/libgloss/riscv/internal_syscall.h
+++ b/libgloss/riscv/internal_syscall.h
@@ -22,31 +22,50 @@ __syscall_error(long a0)
}
static inline long
-__internal_syscall(long n, long _a0, long _a1, long _a2, long _a3, long _a4, long _a5)
+__internal_syscall(long n, int argc, long _a0, long _a1, long _a2, long _a3, long _a4, long _a5)
{
+#ifdef __riscv_32e
+ register long syscall_id asm("t0") = n;
+#else
+ register long syscall_id asm("a7") = n;
+#endif
+
register long a0 asm("a0") = _a0;
+ if (argc < 2) {
+ asm volatile ("ecall" : "+r"(a0) : "r"(syscall_id));
+ return a0;
+ }
register long a1 asm("a1") = _a1;
+ if (argc == 2) {
+ asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(syscall_id));
+ return a0;
+ }
register long a2 asm("a2") = _a2;
+ if (argc == 3) {
+ asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(a2), "r"(syscall_id));
+ return a0;
+ }
register long a3 asm("a3") = _a3;
+ if (argc == 4) {
+ asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(a2), "r"(a3), "r"(syscall_id));
+ return a0;
+ }
register long a4 asm("a4") = _a4;
+ if (argc == 5) {
+ asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(a2), "r"(a3), "r"(a4), "r"(syscall_id));
+ return a0;
+ }
register long a5 asm("a5") = _a5;
-#ifdef __riscv_32e
- register long syscall_id asm("t0") = n;
-#else
- register long syscall_id asm("a7") = n;
-#endif
-
- asm volatile ("scall"
- : "+r"(a0) : "r"(a1), "r"(a2), "r"(a3), "r"(a4), "r"(a5), "r"(syscall_id));
+ asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(a2), "r"(a3), "r"(a4), "r"(a5), "r"(syscall_id));
return a0;
}
static inline long
-syscall_errno(long n, long _a0, long _a1, long _a2, long _a3, long _a4, long _a5)
+syscall_errno(long n, int argc, long _a0, long _a1, long _a2, long _a3, long _a4, long _a5)
{
- long a0 = __internal_syscall (n, _a0, _a1, _a2, _a3, _a4, _a5);
+ long a0 = __internal_syscall (n, argc, _a0, _a1, _a2, _a3, _a4, _a5);
if (a0 < 0)
return __syscall_error (a0);
diff --git a/libgloss/riscv/sys_access.c b/libgloss/riscv/sys_access.c
index ef446d2..45bedb3 100644
--- a/libgloss/riscv/sys_access.c
+++ b/libgloss/riscv/sys_access.c
@@ -5,5 +5,5 @@
int
_access(const char *file, int mode)
{
- return syscall_errno (SYS_access, file, mode, 0, 0, 0, 0);
+ return syscall_errno (SYS_access, 2, file, mode, 0, 0, 0, 0);
}
diff --git a/libgloss/riscv/sys_close.c b/libgloss/riscv/sys_close.c
index 80b10c6..c1691d8 100644
--- a/libgloss/riscv/sys_close.c
+++ b/libgloss/riscv/sys_close.c
@@ -5,5 +5,5 @@
int
_close(int file)
{
- return syscall_errno (SYS_close, file, 0, 0, 0, 0, 0);
+ return syscall_errno (SYS_close, 1, file, 0, 0, 0, 0, 0);
}
diff --git a/libgloss/riscv/sys_exit.c b/libgloss/riscv/sys_exit.c
index 03e1c34..995dd65 100644
--- a/libgloss/riscv/sys_exit.c
+++ b/libgloss/riscv/sys_exit.c
@@ -5,6 +5,6 @@
void
_exit(int exit_status)
{
- syscall_errno (SYS_exit, exit_status, 0, 0, 0, 0, 0);
+ syscall_errno (SYS_exit, 1, exit_status, 0, 0, 0, 0, 0);
while (1);
}
diff --git a/libgloss/riscv/sys_faccessat.c b/libgloss/riscv/sys_faccessat.c
index e966a4a..6418ef4 100644
--- a/libgloss/riscv/sys_faccessat.c
+++ b/libgloss/riscv/sys_faccessat.c
@@ -4,5 +4,5 @@
/* Permissions of a file (by name) in a given directory. */
int _faccessat(int dirfd, const char *file, int mode, int flags)
{
- return syscall_errno (SYS_faccessat, dirfd, file, mode, flags, 0, 0);
+ return syscall_errno (SYS_faccessat, 4, dirfd, file, mode, flags, 0, 0);
}
diff --git a/libgloss/riscv/sys_fstat.c b/libgloss/riscv/sys_fstat.c
index 13a0bca..d97ba44 100644
--- a/libgloss/riscv/sys_fstat.c
+++ b/libgloss/riscv/sys_fstat.c
@@ -9,7 +9,7 @@ int
_fstat(int file, struct stat *st)
{
struct kernel_stat kst;
- int rv = syscall_errno (SYS_fstat, file, &kst, 0, 0, 0, 0);
+ int rv = syscall_errno (SYS_fstat, 2, file, &kst, 0, 0, 0, 0);
_conv_stat (st, &kst);
return rv;
}
diff --git a/libgloss/riscv/sys_fstatat.c b/libgloss/riscv/sys_fstatat.c
index 0e4ea42..bf03355 100644
--- a/libgloss/riscv/sys_fstatat.c
+++ b/libgloss/riscv/sys_fstatat.c
@@ -8,7 +8,7 @@ int
_fstatat(int dirfd, const char *file, struct stat *st, int flags)
{
struct kernel_stat kst;
- int rv = syscall_errno (SYS_fstatat, dirfd, file, &kst, flags, 0, 0);
+ int rv = syscall_errno (SYS_fstatat, 4, dirfd, file, &kst, flags, 0, 0);
_conv_stat (st, &kst);
return rv;
}
diff --git a/libgloss/riscv/sys_gettimeofday.c b/libgloss/riscv/sys_gettimeofday.c
index 457dcbc..daa14e4 100644
--- a/libgloss/riscv/sys_gettimeofday.c
+++ b/libgloss/riscv/sys_gettimeofday.c
@@ -6,5 +6,5 @@
int
_gettimeofday(struct timeval *tp, void *tzp)
{
- return syscall_errno (SYS_gettimeofday, tp, 0, 0, 0, 0, 0);
+ return syscall_errno (SYS_gettimeofday, 1, tp, 0, 0, 0, 0, 0);
}
diff --git a/libgloss/riscv/sys_link.c b/libgloss/riscv/sys_link.c
index eaeb22b..83cd1b2 100644
--- a/libgloss/riscv/sys_link.c
+++ b/libgloss/riscv/sys_link.c
@@ -4,5 +4,5 @@
/* Establish a new name for an existing file. */
int _link(const char *old_name, const char *new_name)
{
- return syscall_errno (SYS_link, old_name, new_name, 0, 0, 0, 0);
+ return syscall_errno (SYS_link, 2, old_name, new_name, 0, 0, 0, 0);
}
diff --git a/libgloss/riscv/sys_lseek.c b/libgloss/riscv/sys_lseek.c
index 7486a3a..8eb8b81 100644
--- a/libgloss/riscv/sys_lseek.c
+++ b/libgloss/riscv/sys_lseek.c
@@ -6,5 +6,5 @@
off_t
_lseek(int file, off_t ptr, int dir)
{
- return syscall_errno (SYS_lseek, file, ptr, dir, 0, 0, 0);
+ return syscall_errno (SYS_lseek, 3, file, ptr, dir, 0, 0, 0);
}
diff --git a/libgloss/riscv/sys_lstat.c b/libgloss/riscv/sys_lstat.c
index 2eeabcc..dd5dc52 100644
--- a/libgloss/riscv/sys_lstat.c
+++ b/libgloss/riscv/sys_lstat.c
@@ -7,7 +7,7 @@
int _lstat(const char *file, struct stat *st)
{
struct kernel_stat kst;
- int rv = syscall_errno (SYS_lstat, file, &kst, 0, 0, 0, 0);
+ int rv = syscall_errno (SYS_lstat, 2, file, &kst, 0, 0, 0, 0);
_conv_stat (st, &kst);
return rv;
}
diff --git a/libgloss/riscv/sys_open.c b/libgloss/riscv/sys_open.c
index 4fd5d67..eb1a99b 100644
--- a/libgloss/riscv/sys_open.c
+++ b/libgloss/riscv/sys_open.c
@@ -5,5 +5,5 @@
int
_open(const char *name, int flags, int mode)
{
- return syscall_errno (SYS_open, name, flags, mode, 0, 0, 0);
+ return syscall_errno (SYS_open, 3, name, flags, mode, 0, 0, 0);
}
diff --git a/libgloss/riscv/sys_openat.c b/libgloss/riscv/sys_openat.c
index cf429b7..652ab2e 100644
--- a/libgloss/riscv/sys_openat.c
+++ b/libgloss/riscv/sys_openat.c
@@ -4,5 +4,5 @@
/* Open file relative to given directory. */
int _openat(int dirfd, const char *name, int flags, int mode)
{
- return syscall_errno (SYS_openat, dirfd, name, flags, mode, 0, 0);
+ return syscall_errno (SYS_openat, 4, dirfd, name, flags, mode, 0, 0);
}
diff --git a/libgloss/riscv/sys_read.c b/libgloss/riscv/sys_read.c
index 7367e26..dd3bc33 100644
--- a/libgloss/riscv/sys_read.c
+++ b/libgloss/riscv/sys_read.c
@@ -5,5 +5,5 @@
/* Read from a file. */
ssize_t _read(int file, void *ptr, size_t len)
{
- return syscall_errno (SYS_read, file, ptr, len, 0, 0, 0);
+ return syscall_errno (SYS_read, 3, file, ptr, len, 0, 0, 0);
}
diff --git a/libgloss/riscv/sys_sbrk.c b/libgloss/riscv/sys_sbrk.c
index f91c2c5..086509e 100644
--- a/libgloss/riscv/sys_sbrk.c
+++ b/libgloss/riscv/sys_sbrk.c
@@ -41,13 +41,13 @@ _sbrk(ptrdiff_t incr)
if (heap_end == 0)
{
- long brk = __internal_syscall (SYS_brk, 0, 0, 0, 0, 0, 0);
+ long brk = __internal_syscall (SYS_brk, 1, 0, 0, 0, 0, 0, 0);
if (brk == -1)
return (void *)__syscall_error (-ENOMEM);
heap_end = brk;
}
- if (__internal_syscall (SYS_brk, heap_end + incr, 0, 0, 0, 0, 0) != heap_end + incr)
+ if (__internal_syscall (SYS_brk, 1, heap_end + incr, 0, 0, 0, 0, 0) != heap_end + incr)
return (void *)__syscall_error (-ENOMEM);
heap_end += incr;
diff --git a/libgloss/riscv/sys_stat.c b/libgloss/riscv/sys_stat.c
index a193b10..1e03700 100644
--- a/libgloss/riscv/sys_stat.c
+++ b/libgloss/riscv/sys_stat.c
@@ -8,7 +8,7 @@ int
_stat(const char *file, struct stat *st)
{
struct kernel_stat kst;
- int rv = syscall_errno (SYS_stat, file, &kst, 0, 0, 0, 0);
+ int rv = syscall_errno (SYS_stat, 2, file, &kst, 0, 0, 0, 0);
_conv_stat (st, &kst);
return rv;
}
diff --git a/libgloss/riscv/sys_unlink.c b/libgloss/riscv/sys_unlink.c
index b55fe1e..1cf6bbe 100644
--- a/libgloss/riscv/sys_unlink.c
+++ b/libgloss/riscv/sys_unlink.c
@@ -5,5 +5,5 @@
int
_unlink(const char *name)
{
- return syscall_errno (SYS_unlink, name, 0, 0, 0, 0, 0);
+ return syscall_errno (SYS_unlink, 1, name, 0, 0, 0, 0, 0);
}
diff --git a/libgloss/riscv/sys_write.c b/libgloss/riscv/sys_write.c
index b972734..ce2edd3 100644
--- a/libgloss/riscv/sys_write.c
+++ b/libgloss/riscv/sys_write.c
@@ -6,5 +6,5 @@
ssize_t
_write(int file, const void *ptr, size_t len)
{
- return syscall_errno (SYS_write, file, ptr, len, 0, 0, 0);
+ return syscall_errno (SYS_write, 3, file, ptr, len, 0, 0, 0);
}
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