kernel/tools/include/nolibc/stdlib.h, branch linux-6.2.y

tools/nolibc: fix missing includes causing build issues at -O0

2023-01-09T17:36:05Z

After the nolibc includes were split to facilitate portability from standard libcs, programs that include only what they need may miss some symbols which are needed by libgcc. This is the case for raise() which is needed by the divide by zero code in some architectures for example. Regardless, being able to include only the apparently needed files is convenient. Instead of trying to move all exported definitions to a single file, since this can change over time, this patch takes another approach consisting in including the nolibc header at the end of all standard include files. This way their types and functions are already known at the moment of inclusion, and including any single one of them is sufficient to bring all the required ones. Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney

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

2022-06-20T16:43:19Z

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()`

2022-04-21T00:05:46Z

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

2022-04-21T00:05:46Z

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

2022-04-21T00:05:45Z

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()

2022-04-21T00:05:45Z

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

2022-04-21T00:05:45Z

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

2022-04-21T00:05:45Z

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

2022-04-21T00:05:45Z

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

2022-04-21T00:05:44Z

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