From: Luis Machado <luis.machado@arm.com>
To: "Torbjörn SVENSSON" <torbjorn.svensson@foss.st.com>,
gdb-patches@sourceware.org
Subject: Re: [PATCH v3] gdb/arm: Cleanup of arm_m_exception_cache
Date: Thu, 11 Aug 2022 09:59:14 +0100 [thread overview]
Message-ID: <8295688a-c75c-8c33-2142-e09f80f77923@arm.com> (raw)
In-Reply-To: <20220810125658.3336503-1-torbjorn.svensson@foss.st.com>
Hi,
On 8/10/22 13:56, Torbjörn SVENSSON wrote:
> With this change, only valid content of LR is accepted for the current
> target. If the content for LR is anything but EXC_RETURN or FNC_RETURN
> will cause GDB to print an error and abover unwinding it's an invalid
> state for the unwinder.
> FNC_RETURN pattern requires Security Extensions to be enabled or GDB
> print an error message and stop unwinding due to the bad state of the
> unwinder.
>
> Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>
> ---
> gdb/arm-tdep.c | 385 ++++++++++++++++++++++++++-----------------------
> 1 file changed, 205 insertions(+), 180 deletions(-)
>
> diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
> index cf8b610a381..93d7d881ea5 100644
> --- a/gdb/arm-tdep.c
> +++ b/gdb/arm-tdep.c
> @@ -3346,19 +3346,7 @@ arm_m_exception_cache (struct frame_info *this_frame)
> {
> struct gdbarch *gdbarch = get_frame_arch (this_frame);
> arm_gdbarch_tdep *tdep = gdbarch_tdep<arm_gdbarch_tdep> (gdbarch);
> - enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
> struct arm_prologue_cache *cache;
> - CORE_ADDR lr;
> - CORE_ADDR sp;
> - CORE_ADDR unwound_sp;
> - uint32_t sp_r0_offset = 0;
> - LONGEST xpsr;
> - uint32_t exc_return;
> - bool fnc_return;
> - uint32_t extended_frame_used;
> - bool secure_stack_used = false;
> - bool default_callee_register_stacking = false;
> - bool exception_domain_is_secure = false;
>
> cache = FRAME_OBSTACK_ZALLOC (struct arm_prologue_cache);
> arm_cache_init (cache, this_frame);
> @@ -3367,8 +3355,8 @@ arm_m_exception_cache (struct frame_info *this_frame)
> describes which bits in LR that define which stack was used prior
> to the exception and if FPU is used (causing extended stack frame). */
>
> - lr = get_frame_register_unsigned (this_frame, ARM_LR_REGNUM);
> - sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
> + CORE_ADDR lr = get_frame_register_unsigned (this_frame, ARM_LR_REGNUM);
> + CORE_ADDR sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
>
> /* ARMv7-M Architecture Reference "A2.3.1 Arm core registers"
> states that LR is set to 0xffffffff on reset. ARMv8-M Architecture
> @@ -3381,19 +3369,30 @@ arm_m_exception_cache (struct frame_info *this_frame)
> return cache;
> }
>
> - fnc_return = (((lr >> 24) & 0xff) == 0xfe);
> - if (tdep->have_sec_ext && fnc_return)
> + /* Check FNC_RETURN indicator bits (24-31). */
> + bool fnc_return = (((lr >> 24) & 0xff) == 0xfe);
> + if (fnc_return)
> {
> + /* FNC_RETURN is only valid for targets with Security Extension. */
> + if (!tdep->have_sec_ext)
> + {
> + error (_ ("While unwinding an exception frame, found unexpected Link "
> + "Register value %s that requires the security extension, "
> + "but the extension was not found or is disabled. This "
> + "should not happen and may be caused by corrupt data or a "
> + "bug in GDB."), phex (lr, ARM_INT_REGISTER_SIZE));
> + }
> +
> if (!arm_unwind_secure_frames)
> {
> - warning (_("Non-secure to secure stack unwinding disabled."));
> + warning (_ ("Non-secure to secure stack unwinding disabled."));
>
> /* Terminate any further stack unwinding by referring to self. */
> arm_cache_set_active_sp_value (cache, tdep, sp);
> return cache;
> }
>
> - xpsr = get_frame_register_unsigned (this_frame, ARM_PS_REGNUM);
> + ULONGEST xpsr = get_frame_register_unsigned (this_frame, ARM_PS_REGNUM);
> if ((xpsr & 0xff) != 0)
> /* Handler mode: This is the mode that exceptions are handled in. */
> arm_cache_switch_prev_sp (cache, tdep, tdep->m_profile_msp_s_regnum);
> @@ -3401,7 +3400,7 @@ arm_m_exception_cache (struct frame_info *this_frame)
> /* Thread mode: This is the normal mode that programs run in. */
> arm_cache_switch_prev_sp (cache, tdep, tdep->m_profile_psp_s_regnum);
>
> - unwound_sp = arm_cache_get_prev_sp_value (cache, tdep);
> + CORE_ADDR unwound_sp = arm_cache_get_prev_sp_value (cache, tdep);
>
> /* Stack layout for a function call from Secure to Non-Secure state
> (ARMv8-M section B3.16):
> @@ -3426,17 +3425,23 @@ arm_m_exception_cache (struct frame_info *this_frame)
> }
>
> /* Check EXC_RETURN indicator bits (24-31). */
> - exc_return = (((lr >> 24) & 0xff) == 0xff);
> + bool exc_return = (((lr >> 24) & 0xff) == 0xff);
> if (exc_return)
> {
> + int sp_regnum;
> + bool secure_stack_used = false;
> + bool default_callee_register_stacking = false;
> + bool exception_domain_is_secure = false;
> + enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
> +
> /* Check EXC_RETURN bit SPSEL if Main or Thread (process) stack used. */
> - bool process_stack_used = ((lr & (1 << 2)) != 0);
> + bool process_stack_used = (bit (lr, 2) != 0);
>
> if (tdep->have_sec_ext)
> {
> - secure_stack_used = ((lr & (1 << 6)) != 0);
> - default_callee_register_stacking = ((lr & (1 << 5)) != 0);
> - exception_domain_is_secure = ((lr & (1 << 0)) == 0);
> + secure_stack_used = (bit (lr, 6) != 0);
> + default_callee_register_stacking = (bit (lr, 5) != 0);
> + exception_domain_is_secure = (bit (lr, 0) == 0);
>
> /* Unwinding from non-secure to secure can trip security
> measures. In order to avoid the debugger being
> @@ -3445,7 +3450,7 @@ arm_m_exception_cache (struct frame_info *this_frame)
> if (secure_stack_used && !exception_domain_is_secure
> && !arm_unwind_secure_frames)
> {
> - warning (_("Non-secure to secure stack unwinding disabled."));
> + warning (_ ("Non-secure to secure stack unwinding disabled."));
>
> /* Terminate any further stack unwinding by referring to self. */
> arm_cache_set_active_sp_value (cache, tdep, sp);
> @@ -3456,188 +3461,208 @@ arm_m_exception_cache (struct frame_info *this_frame)
> {
> if (secure_stack_used)
> /* Secure thread (process) stack used, use PSP_S as SP. */
> - arm_cache_switch_prev_sp (cache, tdep, tdep->m_profile_psp_s_regnum);
> + sp_regnum = tdep->m_profile_psp_s_regnum;
> else
> /* Non-secure thread (process) stack used, use PSP_NS as SP. */
> - arm_cache_switch_prev_sp (cache, tdep, tdep->m_profile_psp_ns_regnum);
> + sp_regnum = tdep->m_profile_psp_ns_regnum;
> }
> else
> {
> if (secure_stack_used)
> /* Secure main stack used, use MSP_S as SP. */
> - arm_cache_switch_prev_sp (cache, tdep, tdep->m_profile_msp_s_regnum);
> + sp_regnum = tdep->m_profile_msp_s_regnum;
> else
> /* Non-secure main stack used, use MSP_NS as SP. */
> - arm_cache_switch_prev_sp (cache, tdep, tdep->m_profile_msp_ns_regnum);
> + sp_regnum = tdep->m_profile_msp_ns_regnum;
> }
> }
> else
> {
> if (process_stack_used)
> /* Thread (process) stack used, use PSP as SP. */
> - arm_cache_switch_prev_sp (cache, tdep, tdep->m_profile_psp_regnum);
> + sp_regnum = tdep->m_profile_psp_regnum;
> else
> /* Main stack used, use MSP as SP. */
> - arm_cache_switch_prev_sp (cache, tdep, tdep->m_profile_msp_regnum);
> - }
> - }
> -
> - /* Fetch the SP to use for this frame. */
> - unwound_sp = arm_cache_get_prev_sp_value (cache, tdep);
> -
> - /* Exception entry context stacking are described in ARMv8-M (section B3.19)
> - and ARMv7-M (sections B1.5.6 and B1.5.7) Architecture Reference Manuals.
> -
> - The following figure shows the structure of the stack frame when Security
> - and Floating-point extensions are present.
> -
> - SP Offsets
> - Without With
> - Callee Regs Callee Regs
> - (Secure -> Non-Secure)
> - +-------------------+
> - 0xA8 | | 0xD0
> - +===================+ --+ <-- Original SP
> - 0xA4 | S31 | 0xCC |
> - +-------------------+ |
> - ... | Additional FP context
> - +-------------------+ |
> - 0x68 | S16 | 0x90 |
> - +===================+ --+
> - 0x64 | Reserved | 0x8C |
> - +-------------------+ |
> - 0x60 | FPSCR | 0x88 |
> - +-------------------+ |
> - 0x5C | S15 | 0x84 | FP context
> - +-------------------+ |
> - ... |
> - +-------------------+ |
> - 0x20 | S0 | 0x48 |
> - +===================+ --+
> - 0x1C | xPSR | 0x44 |
> - +-------------------+ |
> - 0x18 | Return address | 0x40 |
> - +-------------------+ |
> - 0x14 | LR(R14) | 0x3C |
> - +-------------------+ |
> - 0x10 | R12 | 0x38 | State context
> - +-------------------+ |
> - 0x0C | R3 | 0x34 |
> - +-------------------+ |
> - ... |
> - +-------------------+ |
> - 0x00 | R0 | 0x28 |
> - +===================+ --+
> - | R11 | 0x24 |
> - +-------------------+ |
> - ... |
> - +-------------------+ | Additional state context
> - | R4 | 0x08 | when transitioning from
> - +-------------------+ | Secure to Non-Secure
> - | Reserved | 0x04 |
> - +-------------------+ |
> - | Magic signature | 0x00 |
> - +===================+ --+ <-- New SP */
> -
> - /* With the Security extension, the hardware saves R4..R11 too. */
> - if (exc_return && tdep->have_sec_ext && secure_stack_used
> - && (!default_callee_register_stacking || exception_domain_is_secure))
> - {
> - /* Read R4..R11 from the integer callee registers. */
> - cache->saved_regs[4].set_addr (unwound_sp + 0x08);
> - cache->saved_regs[5].set_addr (unwound_sp + 0x0C);
> - cache->saved_regs[6].set_addr (unwound_sp + 0x10);
> - cache->saved_regs[7].set_addr (unwound_sp + 0x14);
> - cache->saved_regs[8].set_addr (unwound_sp + 0x18);
> - cache->saved_regs[9].set_addr (unwound_sp + 0x1C);
> - cache->saved_regs[10].set_addr (unwound_sp + 0x20);
> - cache->saved_regs[11].set_addr (unwound_sp + 0x24);
> - sp_r0_offset = 0x28;
> - }
> -
> - /* The hardware saves eight 32-bit words, comprising xPSR,
> - ReturnAddress, LR (R14), R12, R3, R2, R1, R0. See details in
> - "B1.5.6 Exception entry behavior" in
> - "ARMv7-M Architecture Reference Manual". */
> - cache->saved_regs[0].set_addr (unwound_sp + sp_r0_offset);
> - cache->saved_regs[1].set_addr (unwound_sp + sp_r0_offset + 0x04);
> - cache->saved_regs[2].set_addr (unwound_sp + sp_r0_offset + 0x08);
> - cache->saved_regs[3].set_addr (unwound_sp + sp_r0_offset + 0x0C);
> - cache->saved_regs[ARM_IP_REGNUM].set_addr (unwound_sp + sp_r0_offset + 0x10);
> - cache->saved_regs[ARM_LR_REGNUM].set_addr (unwound_sp + sp_r0_offset + 0x14);
> - cache->saved_regs[ARM_PC_REGNUM].set_addr (unwound_sp + sp_r0_offset + 0x18);
> - cache->saved_regs[ARM_PS_REGNUM].set_addr (unwound_sp + sp_r0_offset + 0x1C);
> -
> - /* Check EXC_RETURN bit FTYPE if extended stack frame (FPU regs stored)
> - type used. */
> - extended_frame_used = ((lr & (1 << 4)) == 0);
> - if (exc_return && extended_frame_used)
> - {
> - int i;
> - int fpu_regs_stack_offset;
> - ULONGEST fpccr;
> -
> - /* Read FPCCR register. */
> - gdb_assert (safe_read_memory_unsigned_integer (FPCCR,
> - ARM_INT_REGISTER_SIZE,
> - byte_order, &fpccr));
> - bool fpccr_ts = bit (fpccr,26);
> -
> - /* This code does not take into account the lazy stacking, see "Lazy
> - context save of FP state", in B1.5.7, also ARM AN298, supported
> - by Cortex-M4F architecture.
> - To fully handle this the FPCCR register (Floating-point Context
> - Control Register) needs to be read out and the bits ASPEN and LSPEN
> - could be checked to setup correct lazy stacked FP registers.
> - This register is located at address 0xE000EF34. */
> -
> - /* Extended stack frame type used. */
> - fpu_regs_stack_offset = unwound_sp + sp_r0_offset + 0x20;
> - for (i = 0; i < 8; i++)
> - {
> - cache->saved_regs[ARM_D0_REGNUM + i].set_addr (fpu_regs_stack_offset);
> - fpu_regs_stack_offset += 8;
> - }
> - cache->saved_regs[ARM_FPSCR_REGNUM].set_addr (unwound_sp + sp_r0_offset + 0x60);
> - fpu_regs_stack_offset += 4;
> + sp_regnum = tdep->m_profile_msp_regnum;
> + }
> +
> + /* Set the active SP regnum. */
> + arm_cache_switch_prev_sp (cache, tdep, sp_regnum);
> +
> + /* Fetch the SP to use for this frame. */
> + CORE_ADDR unwound_sp = arm_cache_get_prev_sp_value (cache, tdep);
> +
> + /* Exception entry context stacking are described in ARMv8-M (section
> + B3.19) and ARMv7-M (sections B1.5.6 and B1.5.7) Architecture Reference
> + Manuals.
> +
> + The following figure shows the structure of the stack frame when
> + Security and Floating-point extensions are present.
> +
> + SP Offsets
> + Without With
> + Callee Regs Callee Regs
> + (Secure -> Non-Secure)
> + +-------------------+
> + 0xA8 | | 0xD0
> + +===================+ --+ <-- Original SP
> + 0xA4 | S31 | 0xCC |
> + +-------------------+ |
> + ... | Additional FP context
> + +-------------------+ |
> + 0x68 | S16 | 0x90 |
> + +===================+ --+
> + 0x64 | Reserved | 0x8C |
> + +-------------------+ |
> + 0x60 | FPSCR | 0x88 |
> + +-------------------+ |
> + 0x5C | S15 | 0x84 | FP context
> + +-------------------+ |
> + ... |
> + +-------------------+ |
> + 0x20 | S0 | 0x48 |
> + +===================+ --+
> + 0x1C | xPSR | 0x44 |
> + +-------------------+ |
> + 0x18 | Return address | 0x40 |
> + +-------------------+ |
> + 0x14 | LR(R14) | 0x3C |
> + +-------------------+ |
> + 0x10 | R12 | 0x38 | State context
> + +-------------------+ |
> + 0x0C | R3 | 0x34 |
> + +-------------------+ |
> + ... |
> + +-------------------+ |
> + 0x00 | R0 | 0x28 |
> + +===================+ --+
> + | R11 | 0x24 |
> + +-------------------+ |
> + ... |
> + +-------------------+ | Additional state
> + | R4 | 0x08 | context when
> + +-------------------+ | transitioning from
> + | Reserved | 0x04 | Secure to Non-Secure
> + +-------------------+ |
> + | Magic signature | 0x00 |
> + +===================+ --+ <-- New SP */
> +
> + uint32_t sp_r0_offset = 0;
> +
> + /* With the Security extension, the hardware saves R4..R11 too. */
> + if (tdep->have_sec_ext && secure_stack_used
> + && (!default_callee_register_stacking || exception_domain_is_secure))
> + {
> + /* Read R4..R11 from the integer callee registers. */
> + cache->saved_regs[4].set_addr (unwound_sp + 0x08);
> + cache->saved_regs[5].set_addr (unwound_sp + 0x0C);
> + cache->saved_regs[6].set_addr (unwound_sp + 0x10);
> + cache->saved_regs[7].set_addr (unwound_sp + 0x14);
> + cache->saved_regs[8].set_addr (unwound_sp + 0x18);
> + cache->saved_regs[9].set_addr (unwound_sp + 0x1C);
> + cache->saved_regs[10].set_addr (unwound_sp + 0x20);
> + cache->saved_regs[11].set_addr (unwound_sp + 0x24);
> + sp_r0_offset = 0x28;
> + }
> +
> + /* The hardware saves eight 32-bit words, comprising xPSR,
> + ReturnAddress, LR (R14), R12, R3, R2, R1, R0. See details in
> + "B1.5.6 Exception entry behavior" in
> + "ARMv7-M Architecture Reference Manual". */
> + cache->saved_regs[0].set_addr (unwound_sp + sp_r0_offset);
> + cache->saved_regs[1].set_addr (unwound_sp + sp_r0_offset + 0x04);
> + cache->saved_regs[2].set_addr (unwound_sp + sp_r0_offset + 0x08);
> + cache->saved_regs[3].set_addr (unwound_sp + sp_r0_offset + 0x0C);
> + cache->saved_regs[ARM_IP_REGNUM].set_addr (unwound_sp + sp_r0_offset
> + + 0x10);
> + cache->saved_regs[ARM_LR_REGNUM].set_addr (unwound_sp + sp_r0_offset
> + + 0x14);
> + cache->saved_regs[ARM_PC_REGNUM].set_addr (unwound_sp + sp_r0_offset
> + + 0x18);
> + cache->saved_regs[ARM_PS_REGNUM].set_addr (unwound_sp + sp_r0_offset
> + + 0x1C);
> +
> + /* Check EXC_RETURN bit FTYPE if extended stack frame (FPU regs stored)
> + type used. */
> + bool extended_frame_used = (bit (lr, 4) == 0);
> + if (extended_frame_used)
> + {
> + ULONGEST fpccr;
> +
> + /* Read FPCCR register. */
> + gdb_assert (safe_read_memory_unsigned_integer (FPCCR,
> + ARM_INT_REGISTER_SIZE,
> + byte_order, &fpccr));
> + bool fpccr_ts = bit (fpccr, 26);
> +
> + /* This code does not take into account the lazy stacking, see "Lazy
> + context save of FP state", in B1.5.7, also ARM AN298, supported
> + by Cortex-M4F architecture.
> + To fully handle this the FPCCR register (Floating-point Context
> + Control Register) needs to be read out and the bits ASPEN and
> + LSPEN could be checked to setup correct lazy stacked FP registers.
> + This register is located at address 0xE000EF34. */
> +
> + /* Extended stack frame type used. */
> + CORE_ADDR addr = unwound_sp + sp_r0_offset + 0x20;
> + for (int i = 0; i < 8; i++)
> + {
> + cache->saved_regs[ARM_D0_REGNUM + i].set_addr (addr);
> + addr += 8;
> + }
> + cache->saved_regs[ARM_FPSCR_REGNUM].set_addr (unwound_sp
> + + sp_r0_offset + 0x60);
> +
> + if (tdep->have_sec_ext && !default_callee_register_stacking
> + && fpccr_ts)
> + {
> + /* Handle floating-point callee saved registers. */
> + addr = unwound_sp + sp_r0_offset + 0x68;
> + for (int i = 8; i < 16; i++)
> + {
> + cache->saved_regs[ARM_D0_REGNUM + i].set_addr (addr);
> + addr += 8;
> + }
>
> - if (tdep->have_sec_ext && !default_callee_register_stacking && fpccr_ts)
> - {
> - /* Handle floating-point callee saved registers. */
> - fpu_regs_stack_offset = unwound_sp + sp_r0_offset + 0x68;
> - for (i = 8; i < 16; i++)
> + arm_cache_set_active_sp_value (cache, tdep,
> + unwound_sp + sp_r0_offset + 0xA8);
> + }
> + else
> {
> - cache->saved_regs[ARM_D0_REGNUM + i].set_addr (fpu_regs_stack_offset);
> - fpu_regs_stack_offset += 8;
> + /* Offset 0x64 is reserved. */
> + arm_cache_set_active_sp_value (cache, tdep,
> + unwound_sp + sp_r0_offset + 0x68);
> }
> -
> - arm_cache_set_active_sp_value (cache, tdep,
> - unwound_sp + sp_r0_offset + 0xA8);
> }
> else
> {
> - /* Offset 0x64 is reserved. */
> + /* Standard stack frame type used. */
> arm_cache_set_active_sp_value (cache, tdep,
> - unwound_sp + sp_r0_offset + 0x68);
> + unwound_sp + sp_r0_offset + 0x20);
> }
> - }
> - else
> - {
> - /* Standard stack frame type used. */
> - arm_cache_set_active_sp_value (cache, tdep,
> - unwound_sp + sp_r0_offset + 0x20);
> - }
>
> - /* If bit 9 of the saved xPSR is set, then there is a four-byte
> - aligner between the top of the 32-byte stack frame and the
> - previous context's stack pointer. */
> - if (safe_read_memory_integer (unwound_sp + sp_r0_offset + 0x1C, 4,
> - byte_order, &xpsr)
> - && (xpsr & (1 << 9)) != 0)
> - arm_cache_set_active_sp_value (cache, tdep,
> - arm_cache_get_prev_sp_value (cache, tdep) + 4);
> + /* If bit 9 of the saved xPSR is set, then there is a four-byte
> + aligner between the top of the 32-byte stack frame and the
> + previous context's stack pointer. */
> + ULONGEST xpsr;
> + gdb_assert (safe_read_memory_unsigned_integer (cache->saved_regs[
> + ARM_PS_REGNUM].addr (), 4,
> + byte_order, &xpsr));
> + if (bit (xpsr, 9) != 0)
> + {
> + CORE_ADDR new_sp = arm_cache_get_prev_sp_value (cache, tdep) + 4;
> + arm_cache_set_active_sp_value (cache, tdep, new_sp);
> + }
>
> - return cache;
> + return cache;
> + }
> +
> + internal_error (__FILE__, __LINE__, _ ("While unwinding an exception frame, "
> + "found unexpected Link Register value "
> + "%s. This should not happen and may "
> + "be caused by corrupt data or a bug in"
> + " GDB."),
> + phex (lr, ARM_INT_REGISTER_SIZE));
> }
>
> /* Implementation of function hook 'this_id' in
This is OK. I pushed it on your behalf.
prev parent reply other threads:[~2022-08-11 8:59 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-10 12:56 Torbjörn SVENSSON
2022-08-11 8:59 ` Luis Machado [this message]
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