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linux/arch/powerpc/kernel/hw_breakpoint_constraints.c
Benjamin Gray 3241f260eb powerpc/watchpoint: Disable pagefaults when getting user instruction
This is called in an atomic context, so is not allowed to sleep if a
user page needs to be faulted in and has nowhere it can be deferred to.
The pagefault_disabled() function is documented as preventing user
access methods from sleeping.

In practice the page will be mapped in nearly always because we are
reading the instruction that just triggered the watchpoint trap.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230829063457.54157-3-bgray@linux.ibm.com
2023-09-18 12:23:47 +10:00

159 lines
4.0 KiB
C

// SPDX-License-Identifier: GPL-2.0+
#include <linux/kernel.h>
#include <linux/uaccess.h>
#include <linux/sched.h>
#include <asm/hw_breakpoint.h>
#include <asm/sstep.h>
#include <asm/cache.h>
static bool dar_in_user_range(unsigned long dar, struct arch_hw_breakpoint *info)
{
return ((info->address <= dar) && (dar - info->address < info->len));
}
static bool ea_user_range_overlaps(unsigned long ea, int size,
struct arch_hw_breakpoint *info)
{
return ((ea < info->address + info->len) &&
(ea + size > info->address));
}
static bool dar_in_hw_range(unsigned long dar, struct arch_hw_breakpoint *info)
{
unsigned long hw_start_addr, hw_end_addr;
hw_start_addr = ALIGN_DOWN(info->address, HW_BREAKPOINT_SIZE);
hw_end_addr = ALIGN(info->address + info->len, HW_BREAKPOINT_SIZE);
return ((hw_start_addr <= dar) && (hw_end_addr > dar));
}
static bool ea_hw_range_overlaps(unsigned long ea, int size,
struct arch_hw_breakpoint *info)
{
unsigned long hw_start_addr, hw_end_addr;
unsigned long align_size = HW_BREAKPOINT_SIZE;
/*
* On p10 predecessors, quadword is handle differently then
* other instructions.
*/
if (!cpu_has_feature(CPU_FTR_ARCH_31) && size == 16)
align_size = HW_BREAKPOINT_SIZE_QUADWORD;
hw_start_addr = ALIGN_DOWN(info->address, align_size);
hw_end_addr = ALIGN(info->address + info->len, align_size);
return ((ea < hw_end_addr) && (ea + size > hw_start_addr));
}
/*
* If hw has multiple DAWR registers, we also need to check all
* dawrx constraint bits to confirm this is _really_ a valid event.
* If type is UNKNOWN, but privilege level matches, consider it as
* a positive match.
*/
static bool check_dawrx_constraints(struct pt_regs *regs, int type,
struct arch_hw_breakpoint *info)
{
if (OP_IS_LOAD(type) && !(info->type & HW_BRK_TYPE_READ))
return false;
/*
* The Cache Management instructions other than dcbz never
* cause a match. i.e. if type is CACHEOP, the instruction
* is dcbz, and dcbz is treated as Store.
*/
if ((OP_IS_STORE(type) || type == CACHEOP) && !(info->type & HW_BRK_TYPE_WRITE))
return false;
if (is_kernel_addr(regs->nip) && !(info->type & HW_BRK_TYPE_KERNEL))
return false;
if (user_mode(regs) && !(info->type & HW_BRK_TYPE_USER))
return false;
return true;
}
/*
* Return true if the event is valid wrt dawr configuration,
* including extraneous exception. Otherwise return false.
*/
bool wp_check_constraints(struct pt_regs *regs, ppc_inst_t instr,
unsigned long ea, int type, int size,
struct arch_hw_breakpoint *info)
{
bool in_user_range = dar_in_user_range(regs->dar, info);
bool dawrx_constraints;
/*
* 8xx supports only one breakpoint and thus we can
* unconditionally return true.
*/
if (IS_ENABLED(CONFIG_PPC_8xx)) {
if (!in_user_range)
info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
return true;
}
if (unlikely(ppc_inst_equal(instr, ppc_inst(0)))) {
if (cpu_has_feature(CPU_FTR_ARCH_31) &&
!dar_in_hw_range(regs->dar, info))
return false;
return true;
}
dawrx_constraints = check_dawrx_constraints(regs, type, info);
if (type == UNKNOWN) {
if (cpu_has_feature(CPU_FTR_ARCH_31) &&
!dar_in_hw_range(regs->dar, info))
return false;
return dawrx_constraints;
}
if (ea_user_range_overlaps(ea, size, info))
return dawrx_constraints;
if (ea_hw_range_overlaps(ea, size, info)) {
if (dawrx_constraints) {
info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
return true;
}
}
return false;
}
void wp_get_instr_detail(struct pt_regs *regs, ppc_inst_t *instr,
int *type, int *size, unsigned long *ea)
{
struct instruction_op op;
int err;
pagefault_disable();
err = __get_user_instr(*instr, (void __user *)regs->nip);
pagefault_enable();
if (err)
return;
analyse_instr(&op, regs, *instr);
*type = GETTYPE(op.type);
*ea = op.ea;
if (!(regs->msr & MSR_64BIT))
*ea &= 0xffffffffUL;
*size = GETSIZE(op.type);
if (*type == CACHEOP) {
*size = l1_dcache_bytes();
*ea &= ~(*size - 1);
} else if (*type == LOAD_VMX || *type == STORE_VMX) {
*ea &= ~(*size - 1);
}
}