From 2d9cf99d9a6c701de912d3e95ea3ffa134af4c62 Mon Sep 17 00:00:00 2001 From: Yvan Roux Date: Thu, 9 Jun 2022 16:44:50 +0200 Subject: [PATCH] gdb/arm: Document and fix exception stack offsets MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Add a description of exception entry context stacking and fix next frame offset (at 0xA8 relative to R0 location) as well as FPU registers ones (starting at 0x68 relative to R0). Signed-off-by: Torbjörn SVENSSON Signed-off-by: Yvan Roux --- gdb/arm-tdep.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 61 insertions(+), 4 deletions(-) diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c index 23f3d5f02f2..456649afdaa 100644 --- a/gdb/arm-tdep.c +++ b/gdb/arm-tdep.c @@ -3429,6 +3429,60 @@ arm_m_exception_cache (struct frame_info *this_frame) /* 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)) @@ -3487,25 +3541,28 @@ arm_m_exception_cache (struct frame_info *this_frame) if (tdep->have_sec_ext && !default_callee_register_stacking) { /* Handle floating-point callee saved registers. */ - fpu_regs_stack_offset = 0x90; + fpu_regs_stack_offset = unwound_sp + sp_r0_offset + 0x68; for (i = 8; i < 16; i++) { cache->saved_regs[ARM_D0_REGNUM + i].set_addr (fpu_regs_stack_offset); fpu_regs_stack_offset += 8; } - arm_cache_set_active_sp_value (cache, tdep, unwound_sp + sp_r0_offset + 0xD0); + arm_cache_set_active_sp_value (cache, tdep, + unwound_sp + sp_r0_offset + 0xA8); } else { /* 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 + 0x68); } } else { /* Standard stack frame type used. */ - arm_cache_set_active_sp_value (cache, tdep, unwound_sp + sp_r0_offset + 0x20); + 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 -- 2.30.2