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Age	Commit message (Collapse)	Author
2022-12-29	samples/bpf: Fix tracex2 by using BPF_KSYSCALL macro	Daniel T. Lee
	Currently, there is a problem with tracex2, as it doesn't print the histogram properly and the results are misleading. (all results report as 0) The problem is caused by a change in arguments of the function to which the kprobe connects. This tracex2 bpf program uses kprobe (attached to __x64_sys_write) to figure out the size of the write system call. In order to achieve this, the third argument 'count' must be intact. The following is a prototype of the sys_write variant. (checked with pfunct) ~/git/linux$ pfunct -P fs/read_write.o \| grep sys_write ssize_t ksys_write(unsigned int fd, const char * buf, size_t count); long int __x64_sys_write(const struct pt_regs * regs); ... cross compile with s390x ... long int __s390_sys_write(struct pt_regs * regs); Since the nature of SYSCALL_WRAPPER function wraps the argument once, additional process of argument extraction is required to properly parse the argument. #define BPF_KSYSCALL(name, args...) ... snip ... struct pt_regs regs = LINUX_HAS_SYSCALL_WRAPPER \ ? (struct pt_regs )PT_REGS_PARM1(ctx) \ : ctx; \ In order to fix this problem, the BPF_SYSCALL macro has been used. This reduces the hassle of parsing arguments from pt_regs. Since the macro uses the CORE version of argument extraction, additional portability comes too. Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20221224071527.2292-5-danieltimlee@gmail.com
2022-12-29	samples/bpf: Change _kern suffix to .bpf with syscall tracing program	Daniel T. Lee
	Currently old compile rule (CLANG-bpf) doesn't contains VMLINUX_H define flag which is essential for the bpf program that includes "vmlinux.h". Also old compile rule doesn't directly specify the compile target as bpf, instead it uses bunch of extra options with clang followed by long chain of commands. (e.g. clang \| opt \| llvm-dis \| llc) In Makefile, there is already new compile rule which is more simple and neat. And it also has -D__VMLINUX_H__ option. By just changing the _kern suffix to .bpf will inherit the benefit of the new CLANG-BPF compile target. Also, this commit adds dummy gnu/stub.h to the samples/bpf directory. As commit 1c2dd16add7e ("selftests/bpf: get rid of -D__x86_64__") noted, compiling with 'clang -target bpf' will raise an error with stubs.h unless workaround (-D__x86_64) is used. This commit solves this problem by adding dummy stub.h to make /usr/include/features.h to follow the expected path as the same way selftests/bpf dealt with. Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20221224071527.2292-4-danieltimlee@gmail.com