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https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/
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276f3b6daf
Mahe reported issue with bpf_override_return helper not working when executed from kprobe.multi bpf program on arm. The problem is that on arm we use alternate storage for pt_regs object that is passed to bpf_prog_run and if any register is changed (which is the case of bpf_override_return) it's not propagated back to actual pt_regs object. Fixing this by introducing and calling ftrace_partial_regs_update function to propagate the values of changed registers (ip and stack). Reported-by: Mahe Tardy <mahe.tardy@gmail.com> Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> Acked-by: Will Deacon <will@kernel.org> Link: https://lore.kernel.org/bpf/20260112121157.854473-1-jolsa@kernel.org
69 lines
2.4 KiB
C
69 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_FTRACE_REGS_H
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#define _LINUX_FTRACE_REGS_H
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/*
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* For archs that just copy pt_regs in ftrace regs, it can use this default.
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* If an architecture does not use pt_regs, it must define all the below
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* accessor functions.
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*/
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#ifndef HAVE_ARCH_FTRACE_REGS
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struct __arch_ftrace_regs {
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struct pt_regs regs;
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};
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#define arch_ftrace_regs(fregs) ((struct __arch_ftrace_regs *)(fregs))
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struct ftrace_regs;
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#define ftrace_regs_get_instruction_pointer(fregs) \
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instruction_pointer(&arch_ftrace_regs(fregs)->regs)
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#define ftrace_regs_get_argument(fregs, n) \
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regs_get_kernel_argument(&arch_ftrace_regs(fregs)->regs, n)
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#define ftrace_regs_get_stack_pointer(fregs) \
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kernel_stack_pointer(&arch_ftrace_regs(fregs)->regs)
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#define ftrace_regs_get_return_value(fregs) \
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regs_return_value(&arch_ftrace_regs(fregs)->regs)
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#define ftrace_regs_set_return_value(fregs, ret) \
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regs_set_return_value(&arch_ftrace_regs(fregs)->regs, ret)
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#define ftrace_override_function_with_return(fregs) \
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override_function_with_return(&arch_ftrace_regs(fregs)->regs)
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#define ftrace_regs_query_register_offset(name) \
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regs_query_register_offset(name)
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#define ftrace_regs_get_frame_pointer(fregs) \
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frame_pointer(&arch_ftrace_regs(fregs)->regs)
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static __always_inline void
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ftrace_partial_regs_update(struct ftrace_regs *fregs, struct pt_regs *regs) { }
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#else
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/*
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* ftrace_partial_regs_update - update the original ftrace_regs from regs
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* @fregs: The ftrace_regs to update from @regs
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* @regs: The partial regs from ftrace_partial_regs() that was updated
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*
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* Some architectures have the partial regs living in the ftrace_regs
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* structure, whereas other architectures need to make a different copy
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* of the @regs. If a partial @regs is retrieved by ftrace_partial_regs() and
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* if the code using @regs updates a field (like the instruction pointer or
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* stack pointer) it may need to propagate that change to the original @fregs
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* it retrieved the partial @regs from. Use this function to guarantee that
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* update happens.
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*/
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static __always_inline void
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ftrace_partial_regs_update(struct ftrace_regs *fregs, struct pt_regs *regs)
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{
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ftrace_regs_set_instruction_pointer(fregs, instruction_pointer(regs));
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ftrace_regs_set_return_value(fregs, regs_return_value(regs));
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}
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#endif /* HAVE_ARCH_FTRACE_REGS */
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/* This can be overridden by the architectures */
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#ifndef FTRACE_REGS_MAX_ARGS
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# define FTRACE_REGS_MAX_ARGS 6
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#endif
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#endif /* _LINUX_FTRACE_REGS_H */
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