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 10/17] powerpc/ftrace: Add separate ftrace_init_nop() with additional validation
Date: Fri, 23 Jun 2023 05:29:27 +0000 [thread overview]
Message-ID: <327c6d9d-8de4-080d-9996-f573d531b308@csgroup.eu> (raw)
In-Reply-To: <f373684081e8e98be09b7f44d2d93069768324dc.1687166935.git.naveen@kernel.org>
Le 19/06/2023 à 11:47, Naveen N Rao a écrit :
> Currently, we validate instructions around the ftrace location every
> time we have to enable/disable ftrace. Introduce ftrace_init_nop() to
> instead perform all the validation during ftrace initialization. This
> allows us to simply patch the necessary instructions during
> enabling/disabling ftrace.
>
> Signed-off-by: Naveen N Rao <naveen@kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/powerpc/include/asm/ftrace.h | 6 +++
> arch/powerpc/kernel/trace/ftrace.c | 71 ++++++++++++++++++++++++++++++
> 2 files changed, 77 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
> index 702aaf2efa966c..ef9f0b97670d1c 100644
> --- a/arch/powerpc/include/asm/ftrace.h
> +++ b/arch/powerpc/include/asm/ftrace.h
> @@ -29,11 +29,17 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
> unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
> unsigned long sp);
>
> +struct module;
> +struct dyn_ftrace;
> struct dyn_arch_ftrace {
> struct module *mod;
> };
>
> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
> +#define ftrace_need_init_nop() (true)
> +int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
> +#define ftrace_init_nop ftrace_init_nop
> +
> struct ftrace_regs {
> struct pt_regs regs;
> };
> diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
> index 278bf8e52b6e89..98bd099c428ee0 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -31,6 +31,16 @@
> #define NUM_FTRACE_TRAMPS 2
> static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS];
>
> +static ppc_inst_t ftrace_create_branch_inst(unsigned long ip, unsigned long addr, int link)
> +{
> + ppc_inst_t op;
> +
> + WARN_ON(!is_offset_in_branch_range(addr - ip));
> + create_branch(&op, (u32 *)ip, addr, link ? BRANCH_SET_LINK : 0);
> +
> + return op;
> +}
> +
> static ppc_inst_t
> ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
> {
> @@ -597,6 +607,67 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
> }
> #endif
>
> +int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
> +{
> + unsigned long addr, ip = rec->ip;
> + ppc_inst_t old, new;
> + int ret = 0;
> +
> + /* Verify instructions surrounding the ftrace location */
> + if (IS_ENABLED(CONFIG_PPC32)) {
> + /* Expected sequence: 'mflr r0', 'stw r0,4(r1)', 'bl _mcount' */
> + ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));
> + if (!ret)
> + ret = ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STW(_R0, _R1, 4)));
> + } else if (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) {
> + /* Expected sequence: 'mflr r0', ['std r0,16(r1)'], 'bl _mcount' */
> + ret = ftrace_read_inst(ip - 4, &old);
> + if (!ret && !ppc_inst_equal(old, ppc_inst(PPC_RAW_MFLR(_R0)))) {
> + ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));
> + ret |= ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STD(_R0, _R1, 16)));
> + }
> + } else {
> + return -EINVAL;
> + }
> +
> + if (ret)
> + return ret;
> +
> + if (!core_kernel_text(ip)) {
> + if (!mod) {
> + pr_err("0x%lx: No module provided for non-kernel address\n", ip);
> + return -EFAULT;
> + }
> + rec->arch.mod = mod;
> + }
> +
> + /* Nop-out the ftrace location */
> + new = ppc_inst(PPC_RAW_NOP());
> + addr = MCOUNT_ADDR;
> + if (is_offset_in_branch_range(addr - ip)) {
> + /* Within range */
> + old = ftrace_create_branch_inst(ip, addr, 1);
> + ret = ftrace_modify_code(ip, old, new);
> + } else if (core_kernel_text(ip) || (IS_ENABLED(CONFIG_MODULES) && mod)) {
> + /*
> + * We would be branching to a linker-generated stub, or to the module _mcount
> + * stub. Let's just confirm we have a 'bl' here.
> + */
> + ret = ftrace_read_inst(ip, &old);
> + if (ret)
> + return ret;
> + if (!is_bl_op(old)) {
> + pr_err("0x%lx: expected (bl) != found (%08lx)\n", ip, ppc_inst_as_ulong(old));
> + return -EINVAL;
> + }
> + ret = patch_instruction((u32 *)ip, new);
> + } else {
> + return -EINVAL;
> + }
> +
> + return ret;
> +}
> +
> int ftrace_update_ftrace_func(ftrace_func_t func)
> {
> unsigned long ip = (unsigned long)(&ftrace_call);
next prev parent reply other threads:[~2023-06-23 5:30 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 [this message]
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
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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