The following commit has been merged into the perf/core branch of tip: Commit-ID: ec6aba3d2be1ed75b3f4c894bb64a36d40db1f55 Gitweb: https://git.kernel.org/tip/ec6aba3d2be1ed75b3f4c894bb64a36d40db1f55 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Tue, 25 May 2021 09:25:19 +02:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Tue, 01 Jun 2021 16:00:08 +02:00 kprobes: Remove kprobe::fault_handler The reason for kprobe::fault_handler(), as given by their comment: * We come here because instructions in the pre/post * handler caused the page_fault, this could happen * if handler tries to access user space by * copy_from_user(), get_user() etc. Let the * user-specified handler try to fix it first. Is just plain bad. Those other handlers are ran from non-preemptible context and had better use _nofault() functions. Also, there is no upstream usage of this. Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Link: https://lore.kernel.org/r/20210525073213.561116662@xxxxxxxxxxxxx --- Documentation/trace/kprobes.rst | 24 +++++------------------- arch/arc/kernel/kprobes.c | 10 ---------- arch/arm/probes/kprobes/core.c | 9 --------- arch/arm64/kernel/probes/kprobes.c | 10 ---------- arch/csky/kernel/probes/kprobes.c | 10 ---------- arch/ia64/kernel/kprobes.c | 9 --------- arch/mips/kernel/kprobes.c | 3 --- arch/powerpc/kernel/kprobes.c | 10 ---------- arch/riscv/kernel/probes/kprobes.c | 10 ---------- arch/s390/kernel/kprobes.c | 10 ---------- arch/sh/kernel/kprobes.c | 10 ---------- arch/sparc/kernel/kprobes.c | 10 ---------- arch/x86/kernel/kprobes/core.c | 10 ---------- include/linux/kprobes.h | 8 -------- kernel/kprobes.c | 19 ------------------- samples/kprobes/kprobe_example.c | 15 --------------- 16 files changed, 5 insertions(+), 172 deletions(-) diff --git a/Documentation/trace/kprobes.rst b/Documentation/trace/kprobes.rst index b757b6d..998149c 100644 --- a/Documentation/trace/kprobes.rst +++ b/Documentation/trace/kprobes.rst @@ -362,14 +362,11 @@ register_kprobe #include <linux/kprobes.h> int register_kprobe(struct kprobe *kp); -Sets a breakpoint at the address kp->addr. When the breakpoint is -hit, Kprobes calls kp->pre_handler. After the probed instruction -is single-stepped, Kprobe calls kp->post_handler. If a fault -occurs during execution of kp->pre_handler or kp->post_handler, -or during single-stepping of the probed instruction, Kprobes calls -kp->fault_handler. Any or all handlers can be NULL. If kp->flags -is set KPROBE_FLAG_DISABLED, that kp will be registered but disabled, -so, its handlers aren't hit until calling enable_kprobe(kp). +Sets a breakpoint at the address kp->addr. When the breakpoint is hit, Kprobes +calls kp->pre_handler. After the probed instruction is single-stepped, Kprobe +calls kp->post_handler. Any or all handlers can be NULL. If kp->flags is set +KPROBE_FLAG_DISABLED, that kp will be registered but disabled, so, its handlers +aren't hit until calling enable_kprobe(kp). .. note:: @@ -415,17 +412,6 @@ User's post-handler (kp->post_handler):: p and regs are as described for the pre_handler. flags always seems to be zero. -User's fault-handler (kp->fault_handler):: - - #include <linux/kprobes.h> - #include <linux/ptrace.h> - int fault_handler(struct kprobe *p, struct pt_regs *regs, int trapnr); - -p and regs are as described for the pre_handler. trapnr is the -architecture-specific trap number associated with the fault (e.g., -on i386, 13 for a general protection fault or 14 for a page fault). -Returns 1 if it successfully handled the exception. - register_kretprobe ------------------ diff --git a/arch/arc/kernel/kprobes.c b/arch/arc/kernel/kprobes.c index cabef45..9f5b39f 100644 --- a/arch/arc/kernel/kprobes.c +++ b/arch/arc/kernel/kprobes.c @@ -324,16 +324,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned long trapnr) kprobes_inc_nmissed_count(cur); /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - - /* * In case the user-specified fault handler returned zero, * try to fix up. */ diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c index a965311..7b9b9a5 100644 --- a/arch/arm/probes/kprobes/core.c +++ b/arch/arm/probes/kprobes/core.c @@ -358,15 +358,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) */ kprobes_inc_nmissed_count(cur); - /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, fsr)) - return 1; break; default: diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index d607c99..f6b088e 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -284,16 +284,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) kprobes_inc_nmissed_count(cur); /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, fsr)) - return 1; - - /* * In case the user-specified fault handler returned * zero, try to fix up. */ diff --git a/arch/csky/kernel/probes/kprobes.c b/arch/csky/kernel/probes/kprobes.c index 589f090..e0e973e 100644 --- a/arch/csky/kernel/probes/kprobes.c +++ b/arch/csky/kernel/probes/kprobes.c @@ -302,16 +302,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr) kprobes_inc_nmissed_count(cur); /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - - /* * In case the user-specified fault handler returned * zero, try to fix up. */ diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c index fc1ff8a..6efed4e 100644 --- a/arch/ia64/kernel/kprobes.c +++ b/arch/ia64/kernel/kprobes.c @@ -851,15 +851,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) kprobes_inc_nmissed_count(cur); /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - /* * In case the user-specified fault handler returned * zero, try to fix up. */ diff --git a/arch/mips/kernel/kprobes.c b/arch/mips/kernel/kprobes.c index 54dfba8..75bff0f 100644 --- a/arch/mips/kernel/kprobes.c +++ b/arch/mips/kernel/kprobes.c @@ -403,9 +403,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - if (kcb->kprobe_status & KPROBE_HIT_SS) { resume_execution(cur, regs, kcb); regs->cp0_status |= kcb->kprobe_old_SR; diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c index 01ab216..75b4e87 100644 --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c @@ -509,16 +509,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) kprobes_inc_nmissed_count(cur); /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - - /* * In case the user-specified fault handler returned * zero, try to fix up. */ diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c index 10b965c..923b5ea 100644 --- a/arch/riscv/kernel/probes/kprobes.c +++ b/arch/riscv/kernel/probes/kprobes.c @@ -284,16 +284,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr) kprobes_inc_nmissed_count(cur); /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - - /* * In case the user-specified fault handler returned * zero, try to fix up. */ diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c index aae24dc..ad631e3 100644 --- a/arch/s390/kernel/kprobes.c +++ b/arch/s390/kernel/kprobes.c @@ -453,16 +453,6 @@ static int kprobe_trap_handler(struct pt_regs *regs, int trapnr) kprobes_inc_nmissed_count(p); /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (p->fault_handler && p->fault_handler(p, regs, trapnr)) - return 1; - - /* * In case the user-specified fault handler returned * zero, try to fix up. */ diff --git a/arch/sh/kernel/kprobes.c b/arch/sh/kernel/kprobes.c index 756100b..5826342 100644 --- a/arch/sh/kernel/kprobes.c +++ b/arch/sh/kernel/kprobes.c @@ -390,16 +390,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) kprobes_inc_nmissed_count(cur); /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - - /* * In case the user-specified fault handler returned * zero, try to fix up. */ diff --git a/arch/sparc/kernel/kprobes.c b/arch/sparc/kernel/kprobes.c index 217c21a..db4e341 100644 --- a/arch/sparc/kernel/kprobes.c +++ b/arch/sparc/kernel/kprobes.c @@ -353,16 +353,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) kprobes_inc_nmissed_count(cur); /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; - - /* * In case the user-specified fault handler returned * zero, try to fix up. */ diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index d3d6554..cfcdf4b 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -1110,16 +1110,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) * these specific fault cases. */ kprobes_inc_nmissed_count(cur); - - /* - * We come here because instructions in the pre/post - * handler caused the page_fault, this could happen - * if handler tries to access user space by - * copy_from_user(), get_user() etc. Let the - * user-specified handler try to fix it first. - */ - if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) - return 1; } return 0; diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h index 1883a4a..523ffc7 100644 --- a/include/linux/kprobes.h +++ b/include/linux/kprobes.h @@ -54,8 +54,6 @@ struct kretprobe_instance; typedef int (*kprobe_pre_handler_t) (struct kprobe *, struct pt_regs *); typedef void (*kprobe_post_handler_t) (struct kprobe *, struct pt_regs *, unsigned long flags); -typedef int (*kprobe_fault_handler_t) (struct kprobe *, struct pt_regs *, - int trapnr); typedef int (*kretprobe_handler_t) (struct kretprobe_instance *, struct pt_regs *); @@ -83,12 +81,6 @@ struct kprobe { /* Called after addr is executed, unless... */ kprobe_post_handler_t post_handler; - /* - * ... called if executing addr causes a fault (eg. page fault). - * Return 1 if it handled fault, otherwise kernel will see it. - */ - kprobe_fault_handler_t fault_handler; - /* Saved opcode (which has been replaced with breakpoint) */ kprobe_opcode_t opcode; diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 745f08f..e41385a 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1183,23 +1183,6 @@ static void aggr_post_handler(struct kprobe *p, struct pt_regs *regs, } NOKPROBE_SYMBOL(aggr_post_handler); -static int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs, - int trapnr) -{ - struct kprobe *cur = __this_cpu_read(kprobe_instance); - - /* - * if we faulted "during" the execution of a user specified - * probe handler, invoke just that probe's fault handler - */ - if (cur && cur->fault_handler) { - if (cur->fault_handler(cur, regs, trapnr)) - return 1; - } - return 0; -} -NOKPROBE_SYMBOL(aggr_fault_handler); - /* Walks the list and increments nmissed count for multiprobe case */ void kprobes_inc_nmissed_count(struct kprobe *p) { @@ -1330,7 +1313,6 @@ static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p) ap->addr = p->addr; ap->flags = p->flags & ~KPROBE_FLAG_OPTIMIZED; ap->pre_handler = aggr_pre_handler; - ap->fault_handler = aggr_fault_handler; /* We don't care the kprobe which has gone. */ if (p->post_handler && !kprobe_gone(p)) ap->post_handler = aggr_post_handler; @@ -2014,7 +1996,6 @@ int register_kretprobe(struct kretprobe *rp) rp->kp.pre_handler = pre_handler_kretprobe; rp->kp.post_handler = NULL; - rp->kp.fault_handler = NULL; /* Pre-allocate memory for max kretprobe instances */ if (rp->maxactive <= 0) { diff --git a/samples/kprobes/kprobe_example.c b/samples/kprobes/kprobe_example.c index c495664..4b2f318 100644 --- a/samples/kprobes/kprobe_example.c +++ b/samples/kprobes/kprobe_example.c @@ -94,26 +94,11 @@ static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs, #endif } -/* - * fault_handler: this is called if an exception is generated for any - * instruction within the pre- or post-handler, or when Kprobes - * single-steps the probed instruction. - */ -static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr) -{ - pr_info("fault_handler: p->addr = 0x%p, trap #%dn", p->addr, trapnr); - /* Return 0 because we don't handle the fault. */ - return 0; -} -/* NOKPROBE_SYMBOL() is also available */ -NOKPROBE_SYMBOL(handler_fault); - static int __init kprobe_init(void) { int ret; kp.pre_handler = handler_pre; kp.post_handler = handler_post; - kp.fault_handler = handler_fault; ret = register_kprobe(&kp); if (ret < 0) {
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