linux-stable.git/tools/include/nolibc/stdlib.h, branch v6.0

tools/nolibc/stdlib: Support overflow checking for older compiler versions

2022-06-20T16:43:19+00:00

Previously, we used __builtin_mul_overflow() to check for overflow in
the multiplication operation in the calloc() function. However, older
compiler versions don't support this built-in. This patch changes the
overflow checking mechanism to make it work on any compiler version
by using a division method to check for overflow. No functional change
intended. While in there, remove the unused variable `void *orig`.

Link: https://lore.kernel.org/lkml/20220330024114.GA18892@1wt.eu
Suggested-by: Willy Tarreau 
Cc: Alviro Iskandar Setiawan 
Signed-off-by: Ammar Faizi 
Acked-by: Willy Tarreau 
Reviewed-by: Alviro Iskandar Setiawan 
Signed-off-by: Paul E. McKenney

tools/nolibc/stdlib: Implement `malloc()`, `calloc()`, `realloc()` and `free()`

2022-04-21T00:05:46+00:00

Implement basic dynamic allocator functions. These functions are
currently only available on architectures that have nolibc mmap()
syscall implemented. These are not a super-fast memory allocator,
but at least they can satisfy basic needs for having heap without
libc.

Cc: David Laight 
Acked-by: Willy Tarreau 
Signed-off-by: Ammar Faizi 
Signed-off-by: Paul E. McKenney

tools/nolibc/stdlib: only reference the external environ when inlined

2022-04-21T00:05:46+00:00

When building with gcc at -O0 we're seeing link errors due to the
"environ" variable being referenced by getenv(). The problem is that
at -O0 gcc will not inline getenv() and will not drop the external
reference. One solution would be to locally declare the variable as
weak, but then it would appear in all programs even those not using
it, and would be confusing to users of getenv() who would forget to
set environ to envp.

An alternate approach used in this patch consists in always inlining
the outer part of getenv() that references this extern so that it's
always dropped when not used. The biggest part of the function was
now moved to a new function called _getenv() that's still not inlined
by default.

Reported-by: Ammar Faizi 
Signed-off-by: Willy Tarreau 
Tested-by: Ammar Faizi 
Signed-off-by: Paul E. McKenney

tools/nolibc/stdlib: add a simple getenv() implementation

2022-04-21T00:05:45+00:00

This implementation relies on an extern definition of the environ
variable, that the caller must declare and initialize from envp.

Signed-off-by: Willy Tarreau 
Signed-off-by: Paul E. McKenney

tools/nolibc/stdlib: implement abort()

2022-04-21T00:05:45+00:00

libgcc uses it for certain divide functions, so it must be exported. Like
for memset() we do that in its own section so that the linker can strip
it when not needed.

Signed-off-by: Willy Tarreau 
Signed-off-by: Paul E. McKenney

tools/nolibc/signal: move raise() to signal.h

2022-04-21T00:05:45+00:00

This function is normally found in signal.h, and providing the file
eases porting of existing programs. Let's move it there.

Signed-off-by: Willy Tarreau 
Signed-off-by: Paul E. McKenney

tools/nolibc/unistd: extract msleep(), sleep(), tcsetpgrp() to unistd.h

2022-04-21T00:05:45+00:00

These functions are normally provided by unistd.h. For ease of porting,
let's create the file and move them there.

Signed-off-by: Willy Tarreau 
Signed-off-by: Paul E. McKenney

tools/nolibc: move exported functions to their own section

2022-04-21T00:05:45+00:00

Some functions like raise() and memcpy() are permanently exported because
they're needed by libgcc on certain platforms. However most of the time
they are not needed and needlessly take space.

Let's move them to their own sub-section, called .text.nolibc_.
This allows ld to get rid of them if unused when passed --gc-sections.

Signed-off-by: Willy Tarreau 
Signed-off-by: Paul E. McKenney

tools/nolibc/stdlib: make raise() use the lower level syscalls only

2022-04-21T00:05:44+00:00

raise() doesn't set errno, so there's no point calling kill(), better
call sys_kill(), which also reduces the function's size.

Signed-off-by: Willy Tarreau 
Signed-off-by: Paul E. McKenney

tools/nolibc/stdlib: avoid a 64-bit shift in u64toh_r()

2022-04-21T00:05:44+00:00

The build of printf() on mips requires libgcc for functions __ashldi3 and
__lshrdi3 due to 64-bit shifts when scanning the input number. These are
not really needed in fact since we scan the number 4 bits at a time. Let's
arrange the loop to perform two 32-bit shifts instead on 32-bit platforms.

Signed-off-by: Willy Tarreau 
Signed-off-by: Paul E. McKenney