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 11/17] powerpc/ftrace: Simplify ftrace_make_nop()
Date: Fri, 23 Jun 2023 05:30:08 +0000 [thread overview]
Message-ID: <5e4eb0eb-591c-d1f2-4092-0def1a033ba9@csgroup.eu> (raw)
In-Reply-To: <e12ccbf28c50c3a07fb614f4d392e55f7098a729.1687166935.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_nop() to patch-in the nop
> without worrying about the instructions surrounding the ftrace location.
> Note that we continue to ensure that we have a bl to
> ftrace_[regs_]caller at the ftrace location before nop-ing it out.
>
> Signed-off-by: Naveen N Rao <naveen@kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/powerpc/kernel/trace/ftrace.c | 220 +++++------------------------
> 1 file changed, 32 insertions(+), 188 deletions(-)
>
> diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
> index 98bd099c428ee0..05153a1038fdff 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -116,112 +116,6 @@ static unsigned long find_bl_target(unsigned long ip, ppc_inst_t op)
> return ip + (long)offset;
> }
>
> -#ifdef CONFIG_MODULES
> -static int
> -__ftrace_make_nop(struct module *mod,
> - struct dyn_ftrace *rec, unsigned long addr)
> -{
> - unsigned long entry, ptr, tramp;
> - unsigned long ip = rec->ip;
> - ppc_inst_t op, pop;
> -
> - /* read where this goes */
> - if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
> - pr_err("Fetching opcode failed.\n");
> - return -EFAULT;
> - }
> -
> - /* Make sure that this is still a 24bit jump */
> - if (!is_bl_op(op)) {
> - pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
> - return -EINVAL;
> - }
> -
> - /* lets find where the pointer goes */
> - tramp = find_bl_target(ip, op);
> -
> - pr_devel("ip:%lx jumps to %lx", ip, 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 (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) {
> - if (copy_inst_from_kernel_nofault(&op, (void *)(ip - 4))) {
> - pr_err("Fetching instruction at %lx failed.\n", ip - 4);
> - return -EFAULT;
> - }
> -
> - /* We expect either a mflr r0, or a std r0, LRSAVE(r1) */
> - if (!ppc_inst_equal(op, ppc_inst(PPC_RAW_MFLR(_R0))) &&
> - !ppc_inst_equal(op, ppc_inst(PPC_INST_STD_LR))) {
> - pr_err("Unexpected instruction %08lx around bl _mcount\n",
> - ppc_inst_as_ulong(op));
> - return -EINVAL;
> - }
> - } else if (IS_ENABLED(CONFIG_PPC64)) {
> - /*
> - * Check what is in the next instruction. We can see ld r2,40(r1), but
> - * on first pass after boot we will see mflr r0.
> - */
> - if (copy_inst_from_kernel_nofault(&op, (void *)(ip + 4))) {
> - pr_err("Fetching op failed.\n");
> - return -EFAULT;
> - }
> -
> - if (!ppc_inst_equal(op, ppc_inst(PPC_INST_LD_TOC))) {
> - pr_err("Expected %08lx found %08lx\n", PPC_INST_LD_TOC,
> - ppc_inst_as_ulong(op));
> - return -EINVAL;
> - }
> - }
> -
> - /*
> - * When using -mprofile-kernel or PPC32 there is no load to jump over.
> - *
> - * Otherwise our original call site looks like:
> - *
> - * bl <tramp>
> - * ld r2,XX(r1)
> - *
> - * Milton Miller pointed out that we can not simply nop the branch.
> - * If a task was preempted when calling a trace function, the nops
> - * will remove the way to restore the TOC in r2 and the r2 TOC will
> - * get corrupted.
> - *
> - * Use a b +8 to jump over the load.
> - * XXX: could make PCREL depend on MPROFILE_KERNEL
> - * XXX: check PCREL && MPROFILE_KERNEL calling sequence
> - */
> - if (IS_ENABLED(CONFIG_MPROFILE_KERNEL) || IS_ENABLED(CONFIG_PPC32))
> - pop = ppc_inst(PPC_RAW_NOP());
> - else
> - pop = ppc_inst(PPC_RAW_BRANCH(8)); /* b +8 */
> -
> - if (patch_instruction((u32 *)ip, pop)) {
> - pr_err("Patching NOP failed.\n");
> - return -EPERM;
> - }
> -
> - return 0;
> -}
> -#else
> -static int __ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
> -{
> - return 0;
> -}
> -#endif /* CONFIG_MODULES */
> -
> static unsigned long find_ftrace_tramp(unsigned long ip)
> {
> int i;
> @@ -235,88 +129,6 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
> return 0;
> }
>
> -static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr)
> -{
> - unsigned long tramp, ip = rec->ip;
> - ppc_inst_t op;
> -
> - /* Read where this goes */
> - if (copy_inst_from_kernel_nofault(&op, (void *)ip)) {
> - pr_err("Fetching opcode failed.\n");
> - return -EFAULT;
> - }
> -
> - /* Make sure that this is still a 24bit jump */
> - if (!is_bl_op(op)) {
> - pr_err("Not expected bl: opcode is %08lx\n", ppc_inst_as_ulong(op));
> - return -EINVAL;
> - }
> -
> - /* Let's find where the pointer goes */
> - tramp = find_bl_target(ip, op);
> -
> - pr_devel("ip:%lx jumps to %lx", ip, tramp);
> -
> - /* Are ftrace trampolines reachable? */
> - if (!find_ftrace_tramp(ip)) {
> - pr_err("No ftrace trampolines reachable from %ps\n", (void *)ip);
> - return -EINVAL;
> - }
> -
> - if (patch_instruction((u32 *)ip, ppc_inst(PPC_RAW_NOP()))) {
> - pr_err("Patching NOP failed.\n");
> - return -EPERM;
> - }
> -
> - return 0;
> -}
> -
> -int ftrace_make_nop(struct module *mod,
> - 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 = ftrace_call_replace(ip, addr, 1);
> - new = ppc_inst(PPC_RAW_NOP());
> - return ftrace_modify_code(ip, old, new);
> - } else if (core_kernel_text(ip)) {
> - return __ftrace_make_nop_kernel(rec, addr);
> - } else if (!IS_ENABLED(CONFIG_MODULES)) {
> - return -EINVAL;
> - }
> -
> - /*
> - * Out of range jumps are called from modules.
> - * We should either already have a pointer to the module
> - * or it has been passed in.
> - */
> - if (!rec->arch.mod) {
> - if (!mod) {
> - pr_err("No module loaded addr=%lx\n", addr);
> - return -EFAULT;
> - }
> - rec->arch.mod = mod;
> - } else if (mod) {
> - if (mod != rec->arch.mod) {
> - pr_err("Record mod %p not equal to passed in mod %p\n",
> - rec->arch.mod, mod);
> - return -EINVAL;
> - }
> - /* nothing to do if mod == rec->arch.mod */
> - } else
> - mod = rec->arch.mod;
> -
> - return __ftrace_make_nop(mod, rec, addr);
> -}
> -
> #ifdef CONFIG_MODULES
> /*
> * Examine the existing instructions for __ftrace_make_call.
> @@ -607,6 +419,38 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
> }
> #endif
>
> +int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
> +{
> + unsigned long tramp, ip = rec->ip;
> + ppc_inst_t old, new;
> +
> + /* Nop-out the ftrace location */
> + new = ppc_inst(PPC_RAW_NOP());
> + if (is_offset_in_branch_range(addr - ip)) {
> + /* Within range */
> + old = 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;
> + }
> + old = 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 */
> + if (!mod)
> + mod = rec->arch.mod;
> + tramp = (addr == (unsigned long)ftrace_caller ? mod->arch.tramp : mod->arch.tramp_regs);
> + old = ftrace_create_branch_inst(ip, tramp, 1);
> + return ftrace_modify_code(ip, old, new);
> + }
> +
> + return -EINVAL;
> +}
> +
> int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
> {
> unsigned long addr, ip = rec->ip;
next prev parent reply other threads:[~2023-06-23 5:31 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 [this message]
2023-06-19 9:47 ` [PATCH 12/17] powerpc/ftrace: Simplify ftrace_make_call() Naveen N Rao
2023-06-23 5:30 ` Christophe Leroy
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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