From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Naveen N Rao <naveen@kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 12/17] powerpc/ftrace: Simplify ftrace_make_call()
Date: Fri, 23 Jun 2023 05:30:32 +0000 [thread overview]
Message-ID: <b2a26ee1-9bae-d0d2-0c73-134c3ebb88c7@csgroup.eu> (raw)
In-Reply-To: <2d28866d2f556488a663981abe5621511efb207b.1687166935.git.naveen@kernel.org>
Le 19/06/2023 à 11:47, Naveen N Rao a écrit :
> Now that we validate the ftrace location during initialization in
> ftrace_init_nop(), we can simplify ftrace_make_call() to replace the nop
> without worrying about the instructions surrounding the ftrace location.
> Note that we continue to ensure that we have a nop at the ftrace
> location before patching it.
>
> Signed-off-by: Naveen N Rao <naveen@kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/powerpc/kernel/trace/ftrace.c | 187 +++++------------------------
> 1 file changed, 31 insertions(+), 156 deletions(-)
>
> diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
> index 05153a1038fdff..6ea8b90246a540 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -129,162 +129,6 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
> return 0;
> }
>
> -#ifdef CONFIG_MODULES
> -/*
> - * Examine the existing instructions for __ftrace_make_call.
> - * They should effectively be a NOP, and follow formal constraints,
> - * depending on the ABI. Return false if they don't.
> - */
> -static bool expected_nop_sequence(void *ip, ppc_inst_t op0, ppc_inst_t op1)
> -{
> - if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
> - return ppc_inst_equal(op0, ppc_inst(PPC_RAW_NOP()));
> - else
> - return ppc_inst_equal(op0, ppc_inst(PPC_RAW_BRANCH(8))) &&
> - ppc_inst_equal(op1, ppc_inst(PPC_INST_LD_TOC));
> -}
> -
> -static int
> -__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> -{
> - ppc_inst_t op[2];
> - void *ip = (void *)rec->ip;
> - unsigned long entry, ptr, tramp;
> - struct module *mod = rec->arch.mod;
> -
> - /* read where this goes */
> - if (copy_inst_from_kernel_nofault(op, ip))
> - return -EFAULT;
> -
> - if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) &&
> - copy_inst_from_kernel_nofault(op + 1, ip + 4))
> - return -EFAULT;
> -
> - if (!expected_nop_sequence(ip, op[0], op[1])) {
> - pr_err("Unexpected call sequence at %p: %08lx %08lx\n", ip,
> - ppc_inst_as_ulong(op[0]), ppc_inst_as_ulong(op[1]));
> - return -EINVAL;
> - }
> -
> - /* If we never set up ftrace trampoline(s), then bail */
> - if (!mod->arch.tramp ||
> - (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && !mod->arch.tramp_regs)) {
> - pr_err("No ftrace trampoline\n");
> - return -EINVAL;
> - }
> -
> - if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) && rec->flags & FTRACE_FL_REGS)
> - tramp = mod->arch.tramp_regs;
> - else
> - tramp = mod->arch.tramp;
> -
> - if (module_trampoline_target(mod, tramp, &ptr)) {
> - pr_err("Failed to get trampoline target\n");
> - return -EFAULT;
> - }
> -
> - pr_devel("trampoline target %lx", ptr);
> -
> - entry = ppc_global_function_entry((void *)addr);
> - /* This should match what was called */
> - if (ptr != entry) {
> - pr_err("addr %lx does not match expected %lx\n", ptr, entry);
> - return -EINVAL;
> - }
> -
> - if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
> - pr_err("REL24 out of range!\n");
> - return -EINVAL;
> - }
> -
> - return 0;
> -}
> -#else
> -static int __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> -{
> - return 0;
> -}
> -#endif /* CONFIG_MODULES */
> -
> -static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr)
> -{
> - ppc_inst_t op;
> - void *ip = (void *)rec->ip;
> - unsigned long tramp, entry, ptr;
> -
> - /* Make sure we're being asked to patch branch to a known ftrace addr */
> - entry = ppc_global_function_entry((void *)ftrace_caller);
> - ptr = ppc_global_function_entry((void *)addr);
> -
> - if (ptr != entry && IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS))
> - entry = ppc_global_function_entry((void *)ftrace_regs_caller);
> -
> - if (ptr != entry) {
> - pr_err("Unknown ftrace addr to patch: %ps\n", (void *)ptr);
> - return -EINVAL;
> - }
> -
> - /* Make sure we have a nop */
> - if (copy_inst_from_kernel_nofault(&op, ip)) {
> - pr_err("Unable to read ftrace location %p\n", ip);
> - return -EFAULT;
> - }
> -
> - if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_NOP()))) {
> - pr_err("Unexpected call sequence at %p: %08lx\n",
> - ip, ppc_inst_as_ulong(op));
> - return -EINVAL;
> - }
> -
> - tramp = find_ftrace_tramp((unsigned long)ip);
> - if (!tramp) {
> - pr_err("No ftrace trampolines reachable from %ps\n", ip);
> - return -EINVAL;
> - }
> -
> - if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
> - pr_err("Error patching branch to ftrace tramp!\n");
> - return -EINVAL;
> - }
> -
> - return 0;
> -}
> -
> -int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> -{
> - unsigned long ip = rec->ip;
> - ppc_inst_t old, new;
> -
> - /*
> - * If the calling address is more that 24 bits away,
> - * then we had to use a trampoline to make the call.
> - * Otherwise just update the call site.
> - */
> - if (test_24bit_addr(ip, addr)) {
> - /* within range */
> - old = ppc_inst(PPC_RAW_NOP());
> - new = ftrace_call_replace(ip, addr, 1);
> - return ftrace_modify_code(ip, old, new);
> - } else if (core_kernel_text(ip)) {
> - return __ftrace_make_call_kernel(rec, addr);
> - } else if (!IS_ENABLED(CONFIG_MODULES)) {
> - /* We should not get here without modules */
> - return -EINVAL;
> - }
> -
> - /*
> - * Out of range jumps are called from modules.
> - * Being that we are converting from nop, it had better
> - * already have a module defined.
> - */
> - if (!rec->arch.mod) {
> - pr_err("No module loaded\n");
> - return -EINVAL;
> - }
> -
> - return __ftrace_make_call(rec, addr);
> -}
> -
> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> #ifdef CONFIG_MODULES
> static int
> @@ -419,6 +263,37 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
> }
> #endif
>
> +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> +{
> + unsigned long tramp, ip = rec->ip;
> + ppc_inst_t old, new;
> + struct module *mod;
> +
> + old = ppc_inst(PPC_RAW_NOP());
> + if (is_offset_in_branch_range(addr - ip)) {
> + /* Within range */
> + new = ftrace_create_branch_inst(ip, addr, 1);
> + return ftrace_modify_code(ip, old, new);
> + } else if (core_kernel_text(ip)) {
> + /* We would be branching to one of our ftrace tramps */
> + tramp = find_ftrace_tramp(ip);
> + if (!tramp) {
> + pr_err("0x%lx: No ftrace trampolines reachable\n", ip);
> + return -EINVAL;
> + }
> + new = ftrace_create_branch_inst(ip, tramp, 1);
> + return ftrace_modify_code(ip, old, new);
> + } else if (IS_ENABLED(CONFIG_MODULES)) {
> + /* Module code would be going to one of the module stubs */
> + mod = rec->arch.mod;
> + tramp = (addr == (unsigned long)ftrace_caller ? mod->arch.tramp : mod->arch.tramp_regs);
> + new = ftrace_create_branch_inst(ip, tramp, 1);
> + return ftrace_modify_code(ip, old, new);
> + }
> +
> + return -EINVAL;
> +}
> +
> int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
> {
> unsigned long tramp, ip = rec->ip;
next prev parent reply other threads:[~2023-06-23 5:32 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-19 9:47 [PATCH 00/17] powerpc/ftrace: refactor and add support for -fpatchable-function-entry Naveen N Rao
2023-06-19 9:47 ` [PATCH 01/17] powerpc/ftrace: Fix dropping weak symbols with older toolchains Naveen N Rao
2023-06-23 5:10 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 02/17] powerpc/module: Remove unused .ftrace.tramp section Naveen N Rao
2023-06-23 5:12 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 03/17] powerpc64/ftrace: Move ELFv1 and -pg support code into a separate file Naveen N Rao
2023-06-23 5:13 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 04/17] powerpc/ftrace: Simplify function_graph support in ftrace.c Naveen N Rao
2023-06-23 5:14 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 05/17] powerpc/ftrace: Use FTRACE_REGS_ADDR to identify the correct ftrace trampoline Naveen N Rao
2023-06-23 5:15 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 06/17] powerpc/ftrace: Extend ftrace support for large kernels to ppc32 Naveen N Rao
2023-06-23 5:21 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 07/17] powerpc/ftrace: Consolidate ftrace support into fewer files Naveen N Rao
2023-06-23 5:25 ` Christophe Leroy
2023-06-28 7:32 ` Naveen N Rao
2023-06-19 9:47 ` [PATCH 08/17] powerpc/ftrace: Refactor ftrace_modify_code() Naveen N Rao
2023-06-23 5:27 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 09/17] powerpc/ftrace: Stop re-purposing linker generated long branches for ftrace Naveen N Rao
2023-06-23 5:28 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 10/17] powerpc/ftrace: Add separate ftrace_init_nop() with additional validation Naveen N Rao
2023-06-23 5:29 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 11/17] powerpc/ftrace: Simplify ftrace_make_nop() Naveen N Rao
2023-06-23 5:30 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 12/17] powerpc/ftrace: Simplify ftrace_make_call() Naveen N Rao
2023-06-23 5:30 ` Christophe Leroy [this message]
2023-06-19 9:47 ` [PATCH 13/17] powerpc/ftrace: Simplify ftrace_modify_call() Naveen N Rao
2023-06-23 5:31 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 14/17] powerpc/ftrace: Replace use of ftrace_call_replace() with ftrace_create_branch_inst() Naveen N Rao
2023-06-23 5:32 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 15/17] powerpc/ftrace: Implement ftrace_replace_code() Naveen N Rao
2023-06-23 5:32 ` Christophe Leroy
2023-06-19 9:47 ` [PATCH 16/17] powerpc/ftrace: Add support for -fpatchable-function-entry Naveen N Rao
2023-06-23 5:37 ` Christophe Leroy
2023-06-28 7:40 ` Naveen N Rao
2023-06-19 9:47 ` [PATCH 17/17] powerpc/ftrace: Create a dummy stackframe to fix stack unwind Naveen N Rao
2023-06-23 5:40 ` Christophe Leroy
2023-06-28 7:43 ` Naveen N Rao
2023-08-23 11:55 ` [PATCH 00/17] powerpc/ftrace: refactor and add support for -fpatchable-function-entry Michael Ellerman
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