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

tools/nolibc: fix the O_* fcntl/open macro definitions for riscv

2023-01-09T17:36:05Z

When RISCV port was imported in 5.2, the O_* macros were taken with their octal value and written as-is in hex, resulting in the getdents64() to fail in nolibc-test. Fixes: 582e84f7b779 ("tool headers nolibc: add RISCV support") #5.2 Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney

tools/nolibc: prevent gcc from making memset() loop over itself

2023-01-09T17:36:05Z

When building on ARM in thumb mode with gcc-11.3 at -O2 or -O3, nolibc-test segfaults during the select() tests. It turns out that at this level, gcc recognizes an opportunity for using memset() to zero the fd_set, but it miscompiles it because it also recognizes a memset pattern as well, and decides to call memset() from the memset() code: 000122bc : 122bc: b510 push {r4, lr} 122be: 0004 movs r4, r0 122c0: 2a00 cmp r2, #0 122c2: d003 beq.n 122cc 122c4: 23ff movs r3, #255 ; 0xff 122c6: 4019 ands r1, r3 122c8: f7ff fff8 bl 122bc 122cc: 0020 movs r0, r4 122ce: bd10 pop {r4, pc} Simply placing an empty asm() statement inside the loop suffices to avoid this. Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney

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: restore mips branch ordering in the _start block

2023-01-09T17:36:05Z

Depending on the compiler used and the optimization options, the sbrk() test was crashing, both on real hardware (mips-24kc) and in qemu. One such example is kernel.org toolchain in version 11.3 optimizing at -Os. Inspecting the sys_brk() call shows the following code: 0040047c : 40047c: 24020fcd li v0,4045 400480: 27bdffe0 addiu sp,sp,-32 400484: 0000000c syscall 400488: 27bd0020 addiu sp,sp,32 40048c: 10e00001 beqz a3,400494 400490: 00021023 negu v0,v0 400494: 03e00008 jr ra It is obviously wrong, the "negu" instruction is placed in beqz's delayed slot, and worse, there's no nop nor instruction after the return, so the next function's first instruction (addiu sip,sip,-32) will also be executed as part of the delayed slot that follows the return. This is caused by the ".set noreorder" directive in the _start block, that applies to the whole program. The compiler emits code without the delayed slots and relies on the compiler to swap instructions when this option is not set. Removing the option would require to change the startup code in a way that wouldn't make it look like the resulting code, which would not be easy to debug. Instead let's just save the default ordering before changing it, and restore it at the end of the _start block. Now the code is correct: 0040047c : 40047c: 24020fcd li v0,4045 400480: 27bdffe0 addiu sp,sp,-32 400484: 0000000c syscall 400488: 10e00002 beqz a3,400494 40048c: 27bd0020 addiu sp,sp,32 400490: 00021023 negu v0,v0 400494: 03e00008 jr ra 400498: 00000000 nop Fixes: 66b6f755ad45 ("rcutorture: Import a copy of nolibc") #5.0 Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney

tools/nolibc: Fix S_ISxxx macros

2023-01-09T17:36:05Z

The mode field has the type encoded as an value in a field, not as a bit mask. Mask the mode with S_IFMT instead of each type to test. Otherwise, false positives are possible: eg S_ISDIR will return true for block devices because S_IFDIR = 0040000 and S_IFBLK = 0060000 since mode is masked with S_IFDIR instead of S_IFMT. These macros now match the similar definitions in tools/include/uapi/linux/stat.h. Signed-off-by: Warner Losh Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney

nolibc: fix fd_set type

2023-01-09T17:36:05Z

The kernel uses unsigned long for the fd_set bitmap, but nolibc use u32. This works fine on little endian machines, but fails on big endian. Convert to unsigned long to fix this. Signed-off-by: Sven Schnelle Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney

tools/nolibc/string: Fix memcmp() implementation

2022-10-28T22:07:02Z

The C standard says that memcmp() must treat the buffers as consisting of "unsigned chars". If char happens to be unsigned, the casts are ok, but then obviously the c1 variable can never contain a negative value. And when char is signed, the casts are wrong, and there's still a problem with using an 8-bit quantity to hold the difference, because that can range from -255 to +255. For example, assuming char is signed, comparing two 1-byte buffers, one containing 0x00 and another 0x80, the current implementation would return -128 for both memcmp(a, b, 1) and memcmp(b, a, 1), whereas one of those should of course return something positive. Signed-off-by: Rasmus Villemoes Fixes: 66b6f755ad45 ("rcutorture: Import a copy of nolibc") Cc: stable@vger.kernel.org # v5.0+ Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney

tools/nolibc: Fix missing strlen() definition and infinite loop with gcc-12

2022-10-28T22:07:02Z

When built at -Os, gcc-12 recognizes an strlen() pattern in nolibc_strlen() and replaces it with a jump to strlen(), which is not defined as a symbol and breaks compilation. Worse, when the function is called strlen(), the function is simply replaced with a jump to itself, hence becomes an infinite loop. One way to avoid this is to always set -ffreestanding, but the calling code doesn't know this and there's no way (either via attributes or pragmas) to globally enable it from include files, effectively leaving a painful situation for the caller. Alexey suggested to place an empty asm() statement inside the loop to stop gcc from recognizing a well-known pattern, which happens to work pretty fine. At least it allows us to make sure our local definition is not replaced with a self jump. The function only needs to be renamed back to strlen() so that the symbol exists, which implies that nolibc_strlen() which is used on variable strings has to be declared as a macro that points back to it before the strlen() macro is redifined. It was verified to produce valid code with gcc 3.4 to 12.1 at different optimization levels, and both with constant and variable strings. In case this problem surfaces again in the future, an alternate approach consisting in adding an optimize("no-tree-loop-distribute-patterns") function attribute for gcc>=12 worked as well but is less pretty. Reported-by: kernel test robot Link: https://lore.kernel.org/r/202210081618.754a77db-yujie.liu@intel.com Fixes: 66b6f755ad45 ("rcutorture: Import a copy of nolibc") Fixes: 96980b833a21 ("tools/nolibc/string: do not use __builtin_strlen() at -O0") Cc: "Paul E. McKenney" Cc: Alexey Dobriyan Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney

tools/nolibc: make sys_mmap() automatically use the right __NR_mmap definition

2022-08-31T12:17:43Z

__NR_mmap2 was used for i386 but it's also needed for other archs such as RISCV32 or ARM. Let's decide to use it based on the __NR_mmap2 definition as it's not defined on other archs. Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney

tools/nolibc: fix build warning in sys_mmap() when my_syscall6 is not defined

2022-08-31T12:17:43Z

We return -ENOSYS when there's no syscall6() operation, but we must cast it to void* to avoid a warning. Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney