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Levin" To: Charlie Jenkins Cc: Celeste Liu , Oleg Nesterov , Paul Walmsley , Palmer Dabbelt , Albert Ou , Eric Biederman , Kees Cook , Alexandre Ghiti , Andrea Bolognani , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Thomas Gleixner , Ron Economos , Felix Yan , Ruizhe Pan , Shiqi Zhang , Guo Ren , Yao Zi , Han Gao , Quan Zhou , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] riscv/ptrace: add new regset to get original a0 register Message-ID: <20241203121948.GA18179@strace.io> References: <20241201-riscv-new-regset-v1-1-c83c58abcc7b@coelacanthus.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Stat-Signature: g3zyuizs4wx1r877ft1ghbfb7mfimuz5 X-Rspamd-Queue-Id: 96A234000E X-Rspam-User: X-HE-Tag: 1733228377-22712 X-HE-Meta: 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 Ojf34/oL AVbyO/naa6YlwqfvnbgYKj87PiCr9Q6IYGErJNvflJXAfSQWdzDaEqVfiGxRk1Y9oHjvWGEabYOADwsVqa8ghrL3jXHwipFeqUjAcGyPXCEQuYzepWErweK1mjE3vHd1X8orb54+0JYHKxvXeuo5yWgLgwuhIOgAN9NMVYExR8ZsIOkRez/TfI75BiNKjcT84ivLzeitK/w/WQIeBPk5b/RU4YCkBy793Ctw0e/gBt/YjRtu5YOCa8IYHia1QPEy0OIdGH2cDmUUBLoY0lqO3VtyshHo+NxtmbNuUe1ByMN7SIWu2D73ZtdU0WIQG+fvvKLO+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Dec 02, 2024 at 09:37:04PM -0800, Charlie Jenkins wrote: [...] > +static void ptrace_test(int opt, int *result) > +{ > + int status; > + pid_t pid; > + struct user_regs_struct regs; > + struct iovec iov = { > + .iov_base = ®s, > + .iov_len = sizeof(regs), > + }; > + > + unsigned long orig_a0; > + struct iovec a0_iov = { > + .iov_base = &orig_a0, > + .iov_len = sizeof(orig_a0), > + }; > + > + pid = fork(); > + if (pid == 0) { > + /* Mark oneself being traced */ > + long val = ptrace(PTRACE_TRACEME, 0, 0, 0); > + if (val) > + perr_and_exit("failed to request for tracer to trace me: %ld\n", val); > + > + kill(getpid(), SIGSTOP); > + > + /* Perform exit syscall that will be intercepted */ > + exit(A0_OLD); > + } > + > + if (pid < 0) > + exit(1); > + > + if (waitpid(pid, &status, 0) != pid) > + perr_and_exit("failed to wait for the tracee %d\n", pid); > + > + /* Stop at the entry point of the syscall */ > + resume_and_wait_tracee(pid, PTRACE_SYSCALL); > + > + /* Check tracee regs before the syscall */ > + if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, &iov)) > + perr_and_exit("failed to get tracee registers\n"); > + if (ptrace(PTRACE_GETREGSET, pid, NT_RISCV_ORIG_A0, &a0_iov)) > + perr_and_exit("failed to get tracee registers\n"); > + if (orig_a0 != A0_OLD) > + perr_and_exit("unexpected orig_a0: 0x%lx\n", orig_a0); > + > + /* Modify a0/orig_a0 for the syscall */ > + switch (opt) { > + case A0_MODIFY: > + regs.a0 = A0_NEW; > + break; Did you mean applying the modified user_regs_struct using PTRACE_SETREGSET? If yes, then there should be an appropriate PTRACE_SETREGSET NT_PRSTATUS call. If no, then regs is ignored, so why would you change it in the first place? > + case ORIG_A0_MODIFY: > + orig_a0 = A0_NEW; > + break; > + } > + > + if (ptrace(PTRACE_SETREGSET, pid, NT_RISCV_ORIG_A0, &a0_iov)) > + perr_and_exit("failed to set tracee registers\n"); > + > + /* Resume the tracee */ > + ptrace(PTRACE_CONT, pid, 0, 0); > + if (waitpid(pid, &status, 0) != pid) > + perr_and_exit("failed to wait for the tracee\n"); > + > + *result = WEXITSTATUS(status); > +} -- ldv