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tracing: Add ftrace_partial_regs() for converting ftrace_regs to pt_regs

Add ftrace_partial_regs() which converts the ftrace_regs to pt_regs.
This is for the eBPF which needs this to keep the same pt_regs interface
to access registers.
Thus when replacing the pt_regs with ftrace_regs in fprobes (which is
used by kprobe_multi eBPF event), this will be used.

If the architecture defines its own ftrace_regs, this copies partial
registers to pt_regs and returns it. If not, ftrace_regs is the same as
pt_regs and ftrace_partial_regs() will return ftrace_regs::regs.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Florent Revest <revest@chromium.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: bpf <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Link: https://lore.kernel.org/173518996761.391279.4987911298206448122.stgit@devnote2
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

authored by

Masami Hiramatsu (Google) and committed by
Steven Rostedt (Google) b9b55c89 762abbc0

+44
+13
arch/arm64/include/asm/ftrace.h
··· 135 135 return arch_ftrace_regs(fregs)->fp; 136 136 } 137 137 138 + static __always_inline struct pt_regs * 139 + ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs) 140 + { 141 + struct __arch_ftrace_regs *afregs = arch_ftrace_regs(fregs); 142 + 143 + memcpy(regs->regs, afregs->regs, sizeof(afregs->regs)); 144 + regs->sp = afregs->sp; 145 + regs->pc = afregs->pc; 146 + regs->regs[29] = afregs->fp; 147 + regs->regs[30] = afregs->lr; 148 + return regs; 149 + } 150 + 138 151 int ftrace_regs_query_register_offset(const char *name); 139 152 140 153 int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
+14
arch/riscv/include/asm/ftrace.h
··· 197 197 arch_ftrace_regs(fregs)->epc = arch_ftrace_regs(fregs)->ra; 198 198 } 199 199 200 + static __always_inline struct pt_regs * 201 + ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs) 202 + { 203 + struct __arch_ftrace_regs *afregs = arch_ftrace_regs(fregs); 204 + 205 + memcpy(&regs->a0, afregs->args, sizeof(afregs->args)); 206 + regs->epc = afregs->epc; 207 + regs->ra = afregs->ra; 208 + regs->sp = afregs->sp; 209 + regs->s0 = afregs->s0; 210 + regs->t1 = afregs->t1; 211 + return regs; 212 + } 213 + 200 214 int ftrace_regs_query_register_offset(const char *name); 201 215 202 216 void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+17
include/linux/ftrace.h
··· 190 190 return arch_ftrace_get_regs(fregs); 191 191 } 192 192 193 + #if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || \ 194 + defined(CONFIG_HAVE_FTRACE_REGS_HAVING_PT_REGS) 195 + 196 + static __always_inline struct pt_regs * 197 + ftrace_partial_regs(struct ftrace_regs *fregs, struct pt_regs *regs) 198 + { 199 + /* 200 + * If CONFIG_HAVE_FTRACE_REGS_HAVING_PT_REGS=y, ftrace_regs memory 201 + * layout is including pt_regs. So always returns that address. 202 + * Since arch_ftrace_get_regs() will check some members and may return 203 + * NULL, we can not use it. 204 + */ 205 + return &arch_ftrace_regs(fregs)->regs; 206 + } 207 + 208 + #endif /* !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS || CONFIG_HAVE_FTRACE_REGS_HAVING_PT_REGS */ 209 + 193 210 /* 194 211 * When true, the ftrace_regs_{get,set}_*() functions may be used on fregs. 195 212 * Note: this can be true even when ftrace_get_regs() cannot provide a pt_regs.