u-boot/arch/arm/lib/interrupts_64.c
Sean Anderson bbe310cdaf arm64: Catch non-emulated semihosting calls
If a debugger is not attached to U-Boot, semihosting calls will raise a
synchronous abort exception. Try to catch this and disable semihosting
so we can e.g. use another uart if one is available. In the immediate
case, we return an error, since it is not always possible to check for
semihosting beforehand (debug uart, user-initiated load command, etc.)

We handle all possible semihosting instructions, which is probably
overkill. However, we do need to keep track of what instruction set
we're using so that we don't suppress an actual error.

A future enhancement could try to determine semihosting capability by
inspecting the processor state.  There's an example of this at [1] for
RISC-V. The equivalent for ARM would inspect the monitor modei
enable/select bits of the DSCR. However, as the article notes, an
exception handler is still helpful in order to catch disconnected
debuggers.

[1] https://tomverbeure.github.io/2021/12/30/Semihosting-on-RISCV.html#avoiding-hangs-when-a-debugger-is-not-connected

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
2022-04-01 16:56:53 -04:00

211 lines
4.4 KiB
C

// SPDX-License-Identifier: GPL-2.0+
/*
* (C) Copyright 2013
* David Feng <fenghua@phytium.com.cn>
*/
#include <common.h>
#include <asm/esr.h>
#include <asm/global_data.h>
#include <asm/ptrace.h>
#include <irq_func.h>
#include <linux/compiler.h>
#include <efi_loader.h>
#include <semihosting.h>
DECLARE_GLOBAL_DATA_PTR;
int interrupt_init(void)
{
enable_interrupts();
return 0;
}
void enable_interrupts(void)
{
return;
}
int disable_interrupts(void)
{
return 0;
}
static void show_efi_loaded_images(struct pt_regs *regs)
{
efi_print_image_infos((void *)regs->elr);
}
static void dump_instr(struct pt_regs *regs)
{
u32 *addr = (u32 *)(regs->elr & ~3UL);
int i;
printf("Code: ");
for (i = -4; i < 1; i++)
printf(i == 0 ? "(%08x) " : "%08x ", addr[i]);
printf("\n");
}
void show_regs(struct pt_regs *regs)
{
int i;
if (gd->flags & GD_FLG_RELOC)
printf("elr: %016lx lr : %016lx (reloc)\n",
regs->elr - gd->reloc_off,
regs->regs[30] - gd->reloc_off);
printf("elr: %016lx lr : %016lx\n", regs->elr, regs->regs[30]);
for (i = 0; i < 29; i += 2)
printf("x%-2d: %016lx x%-2d: %016lx\n",
i, regs->regs[i], i+1, regs->regs[i+1]);
printf("\n");
dump_instr(regs);
}
/*
* Try to "emulate" a semihosting call in the event that we don't have a
* debugger attached.
*/
static bool smh_emulate_trap(struct pt_regs *regs)
{
int size;
if (ESR_ELx_EC(regs->esr) != ESR_ELx_EC_UNKNOWN)
return false;
if (regs->spsr & PSR_MODE32_BIT) {
if (regs->spsr & PSR_AA32_T_BIT) {
u16 *insn = (u16 *)ALIGN_DOWN(regs->elr, 2);
if (*insn != SMH_T32_SVC && *insn != SMH_T32_HLT)
return false;
size = 2;
} else {
u32 *insn = (u32 *)ALIGN_DOWN(regs->elr, 4);
if (*insn != SMH_A32_SVC && *insn != SMH_A32_HLT)
return false;
size = 4;
}
} else {
u32 *insn = (u32 *)ALIGN_DOWN(regs->elr, 4);
if (*insn != SMH_A64_HLT)
return false;
size = 4;
}
/* Avoid future semihosting calls */
disable_semihosting();
/* Just pretend the call failed */
regs->regs[0] = -1;
regs->elr += size;
return true;
}
/*
* do_bad_sync handles the impossible case in the Synchronous Abort vector.
*/
void do_bad_sync(struct pt_regs *pt_regs)
{
efi_restore_gd();
printf("Bad mode in \"Synchronous Abort\" handler, esr 0x%08lx\n",
pt_regs->esr);
show_regs(pt_regs);
show_efi_loaded_images(pt_regs);
panic("Resetting CPU ...\n");
}
/*
* do_bad_irq handles the impossible case in the Irq vector.
*/
void do_bad_irq(struct pt_regs *pt_regs)
{
efi_restore_gd();
printf("Bad mode in \"Irq\" handler, esr 0x%08lx\n", pt_regs->esr);
show_regs(pt_regs);
show_efi_loaded_images(pt_regs);
panic("Resetting CPU ...\n");
}
/*
* do_bad_fiq handles the impossible case in the Fiq vector.
*/
void do_bad_fiq(struct pt_regs *pt_regs)
{
efi_restore_gd();
printf("Bad mode in \"Fiq\" handler, esr 0x%08lx\n", pt_regs->esr);
show_regs(pt_regs);
show_efi_loaded_images(pt_regs);
panic("Resetting CPU ...\n");
}
/*
* do_bad_error handles the impossible case in the Error vector.
*/
void do_bad_error(struct pt_regs *pt_regs)
{
efi_restore_gd();
printf("Bad mode in \"Error\" handler, esr 0x%08lx\n", pt_regs->esr);
show_regs(pt_regs);
show_efi_loaded_images(pt_regs);
panic("Resetting CPU ...\n");
}
/*
* do_sync handles the Synchronous Abort exception.
*/
void do_sync(struct pt_regs *pt_regs)
{
if (CONFIG_IS_ENABLED(SEMIHOSTING_FALLBACK) &&
smh_emulate_trap(pt_regs))
return;
efi_restore_gd();
printf("\"Synchronous Abort\" handler, esr 0x%08lx\n", pt_regs->esr);
show_regs(pt_regs);
show_efi_loaded_images(pt_regs);
panic("Resetting CPU ...\n");
}
/*
* do_irq handles the Irq exception.
*/
void do_irq(struct pt_regs *pt_regs)
{
efi_restore_gd();
printf("\"Irq\" handler, esr 0x%08lx\n", pt_regs->esr);
show_regs(pt_regs);
show_efi_loaded_images(pt_regs);
panic("Resetting CPU ...\n");
}
/*
* do_fiq handles the Fiq exception.
*/
void do_fiq(struct pt_regs *pt_regs)
{
efi_restore_gd();
printf("\"Fiq\" handler, esr 0x%08lx\n", pt_regs->esr);
show_regs(pt_regs);
show_efi_loaded_images(pt_regs);
panic("Resetting CPU ...\n");
}
/*
* do_error handles the Error exception.
* Errors are more likely to be processor specific,
* it is defined with weak attribute and can be redefined
* in processor specific code.
*/
void __weak do_error(struct pt_regs *pt_regs)
{
efi_restore_gd();
printf("\"Error\" handler, esr 0x%08lx\n", pt_regs->esr);
show_regs(pt_regs);
show_efi_loaded_images(pt_regs);
panic("Resetting CPU ...\n");
}