![Linus Torvalds](/assets/img/avatar_default.png)
Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument of the user address range verification function since we got rid of the old racy i386-only code to walk page tables by hand. It existed because the original 80386 would not honor the write protect bit when in kernel mode, so you had to do COW by hand before doing any user access. But we haven't supported that in a long time, and these days the 'type' argument is a purely historical artifact. A discussion about extending 'user_access_begin()' to do the range checking resulted this patch, because there is no way we're going to move the old VERIFY_xyz interface to that model. And it's best done at the end of the merge window when I've done most of my merges, so let's just get this done once and for all. This patch was mostly done with a sed-script, with manual fix-ups for the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form. There were a couple of notable cases: - csky still had the old "verify_area()" name as an alias. - the iter_iov code had magical hardcoded knowledge of the actual values of VERIFY_{READ,WRITE} (not that they mattered, since nothing really used it) - microblaze used the type argument for a debug printout but other than those oddities this should be a total no-op patch. I tried to fix up all architectures, did fairly extensive grepping for access_ok() uses, and the changes are trivial, but I may have missed something. Any missed conversion should be trivially fixable, though. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
178 lines
4.5 KiB
C
178 lines
4.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/oprofile.h>
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/uaccess.h>
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#include <asm/ptrace.h>
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#include <asm/stacktrace.h>
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#include <linux/stacktrace.h>
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#include <linux/kernel.h>
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#include <asm/sections.h>
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#include <asm/inst.h>
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struct stackframe {
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unsigned long sp;
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unsigned long pc;
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unsigned long ra;
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};
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static inline int get_mem(unsigned long addr, unsigned long *result)
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{
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unsigned long *address = (unsigned long *) addr;
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if (!access_ok(address, sizeof(unsigned long)))
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return -1;
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if (__copy_from_user_inatomic(result, address, sizeof(unsigned long)))
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return -3;
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return 0;
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}
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/*
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* These two instruction helpers were taken from process.c
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*/
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static inline int is_ra_save_ins(union mips_instruction *ip)
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{
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/* sw / sd $ra, offset($sp) */
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return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op)
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&& ip->i_format.rs == 29 && ip->i_format.rt == 31;
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}
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static inline int is_sp_move_ins(union mips_instruction *ip)
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{
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/* addiu/daddiu sp,sp,-imm */
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if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
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return 0;
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if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
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return 1;
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return 0;
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}
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/*
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* Looks for specific instructions that mark the end of a function.
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* This usually means we ran into the code area of the previous function.
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*/
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static inline int is_end_of_function_marker(union mips_instruction *ip)
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{
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/* jr ra */
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if (ip->r_format.func == jr_op && ip->r_format.rs == 31)
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return 1;
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/* lui gp */
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if (ip->i_format.opcode == lui_op && ip->i_format.rt == 28)
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return 1;
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return 0;
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}
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/*
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* TODO for userspace stack unwinding:
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* - handle cases where the stack is adjusted inside a function
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* (generally doesn't happen)
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* - find optimal value for max_instr_check
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* - try to find a better way to handle leaf functions
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*/
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static inline int unwind_user_frame(struct stackframe *old_frame,
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const unsigned int max_instr_check)
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{
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struct stackframe new_frame = *old_frame;
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off_t ra_offset = 0;
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size_t stack_size = 0;
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unsigned long addr;
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if (old_frame->pc == 0 || old_frame->sp == 0 || old_frame->ra == 0)
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return -9;
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for (addr = new_frame.pc; (addr + max_instr_check > new_frame.pc)
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&& (!ra_offset || !stack_size); --addr) {
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union mips_instruction ip;
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if (get_mem(addr, (unsigned long *) &ip))
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return -11;
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if (is_sp_move_ins(&ip)) {
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int stack_adjustment = ip.i_format.simmediate;
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if (stack_adjustment > 0)
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/* This marks the end of the previous function,
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which means we overran. */
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break;
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stack_size = (unsigned long) stack_adjustment;
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} else if (is_ra_save_ins(&ip)) {
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int ra_slot = ip.i_format.simmediate;
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if (ra_slot < 0)
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/* This shouldn't happen. */
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break;
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ra_offset = ra_slot;
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} else if (is_end_of_function_marker(&ip))
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break;
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}
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if (!ra_offset || !stack_size)
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goto done;
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if (ra_offset) {
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new_frame.ra = old_frame->sp + ra_offset;
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if (get_mem(new_frame.ra, &(new_frame.ra)))
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return -13;
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}
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if (stack_size) {
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new_frame.sp = old_frame->sp + stack_size;
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if (get_mem(new_frame.sp, &(new_frame.sp)))
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return -14;
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}
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if (new_frame.sp > old_frame->sp)
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return -2;
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done:
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new_frame.pc = old_frame->ra;
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*old_frame = new_frame;
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return 0;
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}
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static inline void do_user_backtrace(unsigned long low_addr,
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struct stackframe *frame,
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unsigned int depth)
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{
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const unsigned int max_instr_check = 512;
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const unsigned long high_addr = low_addr + THREAD_SIZE;
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while (depth-- && !unwind_user_frame(frame, max_instr_check)) {
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oprofile_add_trace(frame->ra);
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if (frame->sp < low_addr || frame->sp > high_addr)
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break;
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}
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}
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#ifndef CONFIG_KALLSYMS
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static inline void do_kernel_backtrace(unsigned long low_addr,
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struct stackframe *frame,
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unsigned int depth) { }
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#else
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static inline void do_kernel_backtrace(unsigned long low_addr,
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struct stackframe *frame,
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unsigned int depth)
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{
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while (depth-- && frame->pc) {
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frame->pc = unwind_stack_by_address(low_addr,
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&(frame->sp),
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frame->pc,
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&(frame->ra));
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oprofile_add_trace(frame->ra);
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}
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}
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#endif
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void notrace op_mips_backtrace(struct pt_regs *const regs, unsigned int depth)
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{
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struct stackframe frame = { .sp = regs->regs[29],
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.pc = regs->cp0_epc,
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.ra = regs->regs[31] };
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const int userspace = user_mode(regs);
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const unsigned long low_addr = ALIGN(frame.sp, THREAD_SIZE);
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if (userspace)
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do_user_backtrace(low_addr, &frame, depth);
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else
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do_kernel_backtrace(low_addr, &frame, depth);
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}
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