Merge branch 'bpf-x86-allow-function-arguments-up-to-12-for-tracing'
Menglong Dong says: ==================== bpf, x86: allow function arguments up to 12 for TRACING From: Menglong Dong <imagedong@tencent.com> For now, the BPF program of type BPF_PROG_TYPE_TRACING can only be used on the kernel functions whose arguments count less than or equal to 6, if not considering '> 8 bytes' struct argument. This is not friendly at all, as too many functions have arguments count more than 6. According to the current kernel version, below is a statistics of the function arguments count: argument count | function count 7 | 704 8 | 270 9 | 84 10 | 47 11 | 47 12 | 27 13 | 22 14 | 5 15 | 0 16 | 1 Therefore, let's enhance it by increasing the function arguments count allowed in arch_prepare_bpf_trampoline(), for now, only x86_64. In the 1st patch, we save/restore regs with BPF_DW size to make the code in save_regs()/restore_regs() simpler. In the 2nd patch, we make arch_prepare_bpf_trampoline() support to copy function arguments in stack for x86 arch. Therefore, the maximum arguments can be up to MAX_BPF_FUNC_ARGS for FENTRY, FEXIT and MODIFY_RETURN. Meanwhile, we clean the potential garbage value when we copy the arguments on-stack. And the 3rd patch is for the testcases of the this series. Changes since v9: - fix the failed test cases of trampoline_count and get_func_args_test in the 3rd patch Changes since v8: - change the way to test fmod_ret in the 3rd patch Changes since v7: - split the testcases, and add fentry_many_args/fexit_many_args to DENYLIST.aarch64 in 3rd patch Changes since v6: - somit nits from commit message and comment in the 1st patch - remove the inline in get_nr_regs() in the 1st patch - rename some function and various in the 1st patch Changes since v5: - adjust the commit log of the 1st patch, avoiding confusing people that bugs exist in current code - introduce get_nr_regs() to get the space that used to pass args on stack correct in the 2nd patch - add testcases to tracing_struct.c instead of fentry_test.c and fexit_test.c Changes since v4: - consider the case of the struct in arguments can't be hold by regs - add comment for some code - add testcases for MODIFY_RETURN - rebase to the latest Changes since v3: - try make the stack pointer 16-byte aligned. Not sure if I'm right :) - introduce clean_garbage() to clean the grabage when argument count is 7 - use different data type in bpf_testmod_fentry_test{7,12} - add testcase for grabage values in ctx Changes since v2: - keep MAX_BPF_FUNC_ARGS still - clean garbage value in upper bytes in the 2nd patch - move bpf_fentry_test{7,12} to bpf_testmod.c and rename them to bpf_testmod_fentry_test{7,12} meanwhile in the 3rd patch Changes since v1: - change the maximun function arguments to 14 from 12 - add testcases (Jiri Olsa) - instead EMIT4 with EMIT3_off32 for "lea" to prevent overflow ==================== Link: https://lore.kernel.org/r/20230713040738.1789742-1-imagedong@tencent.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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