synth-backend 0.8.0

//! MPU Region Allocator
//!
//! Allocates MPU regions for WebAssembly linear memories

use crate::mpu::{MPUAttributes, MPUPermissions, MPURegion, MPUSize};
use synth_core::{Error, HardwareCapabilities, Memory, Result};

/// Request for MPU region allocation
#[derive(Debug, Clone)]
pub struct MPUAllocationRequest {
    /// Memory to protect
    pub memory: Memory,

    /// Desired permissions
    pub permissions: MPUPermissions,

    /// Memory attributes
    pub attributes: MPUAttributes,

    /// Preferred base address (None = allocator chooses)
    pub preferred_base: Option<u32>,
}

/// MPU Region Allocator
pub struct MPUAllocator {
    /// Hardware capabilities
    hw_caps: HardwareCapabilities,

    /// Allocated regions
    allocated: Vec<MPURegion>,
}

impl MPUAllocator {
    /// Create a new allocator
    pub fn new(hw_caps: HardwareCapabilities) -> Self {
        Self {
            hw_caps,
            allocated: Vec::new(),
        }
    }

    /// Allocate MPU regions for a memory
    pub fn allocate(&mut self, request: MPUAllocationRequest) -> Result<Vec<MPURegion>> {
        // Calculate required size in bytes
        let size_bytes = request.memory.initial as u64 * 65536; // Pages to bytes

        // Check if we have available regions
        if self.allocated.len() >= self.hw_caps.mpu_regions as usize {
            return Err(Error::HardwareProtectionError(format!(
                "No MPU regions available (max: {})",
                self.hw_caps.mpu_regions
            )));
        }

        // Calculate MPU size (must be power of 2)
        let mpu_size = MPUSize::from_bytes(size_bytes)?;
        let actual_size = mpu_size.bytes();

        // Determine base address
        let base_address = request.preferred_base.unwrap_or(0x20000000);

        // Align base address to region size
        let alignment = actual_size as u32;
        let aligned_base = (base_address + alignment - 1) & !(alignment - 1);

        // Create region
        let region_number = self.allocated.len() as u8;
        let mut region = MPURegion::new(region_number, aligned_base, mpu_size);
        region.permissions = request.permissions;
        region.attributes = request.attributes;

        // Validate region
        region.validate()?;

        // Check for overlaps with existing regions
        for existing in &self.allocated {
            if self.regions_overlap(&region, existing) {
                return Err(Error::HardwareProtectionError(format!(
                    "Region overlap detected: 0x{:08X} overlaps with existing region at 0x{:08X}",
                    region.base_address, existing.base_address
                )));
            }
        }

        // Store allocated region
        self.allocated.push(region.clone());

        Ok(vec![region])
    }

    /// Check if two regions overlap
    fn regions_overlap(&self, r1: &MPURegion, r2: &MPURegion) -> bool {
        let r1_start = r1.base_address as u64;
        let r1_end = r1_start + r1.size.bytes();
        let r2_start = r2.base_address as u64;
        let r2_end = r2_start + r2.size.bytes();

        // Check overlap
        !(r1_end <= r2_start || r2_end <= r1_start)
    }

    /// Get all allocated regions
    pub fn allocated_regions(&self) -> &[MPURegion] {
        &self.allocated
    }

    /// Get number of available regions
    pub fn available_regions(&self) -> u8 {
        self.hw_caps.mpu_regions - self.allocated.len() as u8
    }

    /// Generate C initialization code for all regions
    pub fn generate_init_code(&self) -> String {
        let mut code = String::new();

        code.push_str("/* MPU Initialization Code */\n");
        code.push_str("/* Generated by Synth WebAssembly Component Synthesizer */\n\n");
        code.push_str("#include <stdint.h>\n\n");
        code.push_str("/* MPU Register Addresses (ARM Cortex-M) */\n");
        code.push_str("#define MPU_TYPE  (*((volatile uint32_t*)0xE000ED90))\n");
        code.push_str("#define MPU_CTRL  (*((volatile uint32_t*)0xE000ED94))\n");
        code.push_str("#define MPU_RNR   (*((volatile uint32_t*)0xE000ED98))\n");
        code.push_str("#define MPU_RBAR  (*((volatile uint32_t*)0xE000ED9C))\n");
        code.push_str("#define MPU_RASR  (*((volatile uint32_t*)0xE000EDA0))\n\n");
        code.push_str("/* MPU Control Register bits */\n");
        code.push_str("#define MPU_CTRL_ENABLE        (1 << 0)\n");
        code.push_str("#define MPU_CTRL_HFNMIENA      (1 << 1)\n");
        code.push_str("#define MPU_CTRL_PRIVDEFENA    (1 << 2)\n\n");
        code.push_str("void mpu_init(void) {\n");
        code.push_str("    /* Disable MPU during configuration */\n");
        code.push_str("    MPU_CTRL = 0;\n\n");

        for region in &self.allocated {
            code.push_str(&format!(
                "    /* Region {}: 0x{:08X} - {} bytes */\n",
                region.number,
                region.base_address,
                region.size.bytes()
            ));
            code.push_str(&format!("    MPU_RNR = {};\n", region.number));
            code.push_str(&format!("    MPU_RBAR = 0x{:08X};\n", region.rbar()));
            code.push_str(&format!("    MPU_RASR = 0x{:08X};\n\n", region.rasr()));
        }

        code.push_str("    /* Enable MPU with default memory map for privileged access */\n");
        code.push_str("    MPU_CTRL = MPU_CTRL_ENABLE | MPU_CTRL_PRIVDEFENA;\n");
        code.push_str("}\n");

        code
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use synth_core::{CortexMVariant, TargetArch};

    fn test_hardware() -> HardwareCapabilities {
        HardwareCapabilities {
            arch: TargetArch::ARMCortexM(CortexMVariant::M4F),
            has_mpu: true,
            mpu_regions: 8,
            has_pmp: false,
            pmp_entries: 0,
            has_fpu: true,
            fpu_precision: Some(synth_core::FPUPrecision::Single),
            has_simd: false,
            simd_level: None,
            xip_capable: true,
            flash_size: 1024 * 1024,
            ram_size: 256 * 1024,
        }
    }

    #[test]
    fn test_allocate_single_region() {
        let mut allocator = MPUAllocator::new(test_hardware());

        let request = MPUAllocationRequest {
            memory: Memory {
                index: 0,
                initial: 1, // 1 page = 64KB
                maximum: None,
                shared: false,
                memory64: false,
            },
            permissions: MPUPermissions::FullRW,
            attributes: MPUAttributes::normal(),
            preferred_base: Some(0x20000000),
        };

        let regions = allocator.allocate(request).unwrap();
        assert_eq!(regions.len(), 1);
        assert_eq!(regions[0].size, MPUSize::Size64KB);
    }

    #[test]
    fn test_available_regions() {
        let mut allocator = MPUAllocator::new(test_hardware());
        assert_eq!(allocator.available_regions(), 8);

        let request = MPUAllocationRequest {
            memory: Memory {
                index: 0,
                initial: 1,
                maximum: None,
                shared: false,
                memory64: false,
            },
            permissions: MPUPermissions::FullRW,
            attributes: MPUAttributes::normal(),
            preferred_base: Some(0x20000000),
        };

        allocator.allocate(request).unwrap();
        assert_eq!(allocator.available_regions(), 7);
    }

    #[test]
    fn test_generate_init_code() {
        let mut allocator = MPUAllocator::new(test_hardware());

        let request = MPUAllocationRequest {
            memory: Memory {
                index: 0,
                initial: 1,
                maximum: None,
                shared: false,
                memory64: false,
            },
            permissions: MPUPermissions::FullRW,
            attributes: MPUAttributes::normal(),
            preferred_base: Some(0x20000000),
        };

        allocator.allocate(request).unwrap();
        let code = allocator.generate_init_code();

        assert!(code.contains("void mpu_init(void)"));
        assert!(code.contains("MPU_CTRL"));
        assert!(code.contains("Region 0"));
    }

    #[test]
    fn test_nrf52840_configuration() {
        // Use actual nRF52840 hardware capabilities
        let hw_caps = HardwareCapabilities::nrf52840();
        let mut allocator = MPUAllocator::new(hw_caps);

        // Allocate regions for a realistic WebAssembly module layout

        // Region 0: .text section (executable code in flash)
        // Flash on nRF52840 starts at 0x00000000
        let text_request = MPUAllocationRequest {
            memory: Memory {
                index: 0,
                initial: 2, // 128KB of code
                maximum: None,
                shared: false,
                memory64: false,
            },
            permissions: MPUPermissions::FullRO,
            attributes: MPUAttributes {
                shareable: false,
                cacheable: true,
                bufferable: false,
                execute_never: false, // Code is executable
            },
            preferred_base: Some(0x00000000), // Flash base
        };

        let text_regions = allocator.allocate(text_request).unwrap();
        assert_eq!(text_regions.len(), 1);
        assert_eq!(text_regions[0].base_address, 0x00000000);
        assert!(text_regions[0].size.bytes() >= 128 * 1024);

        // Region 1: .rodata section (read-only data in flash)
        let rodata_request = MPUAllocationRequest {
            memory: Memory {
                index: 1,
                initial: 1, // 64KB of read-only data
                maximum: None,
                shared: false,
                memory64: false,
            },
            permissions: MPUPermissions::FullRO,
            attributes: MPUAttributes {
                shareable: false,
                cacheable: true,
                bufferable: false,
                execute_never: true, // Data is not executable
            },
            preferred_base: Some(0x00020000), // After .text
        };

        let rodata_regions = allocator.allocate(rodata_request).unwrap();
        assert_eq!(rodata_regions.len(), 1);

        // Region 2: .data/.bss section (read-write data in RAM)
        // RAM on nRF52840 starts at 0x20000000
        let data_request = MPUAllocationRequest {
            memory: Memory {
                index: 2,
                initial: 1, // 64KB of RAM
                maximum: None,
                shared: false,
                memory64: false,
            },
            permissions: MPUPermissions::FullRW,
            attributes: MPUAttributes::normal(),
            preferred_base: Some(0x20000000), // RAM base
        };

        let data_regions = allocator.allocate(data_request).unwrap();
        assert_eq!(data_regions.len(), 1);
        assert_eq!(data_regions[0].base_address, 0x20000000);
        assert_eq!(data_regions[0].permissions, MPUPermissions::FullRW);

        // Verify we've used 3 regions out of 8
        assert_eq!(allocator.available_regions(), 5);
        assert_eq!(allocator.allocated_regions().len(), 3);

        // Generate C initialization code
        let init_code = allocator.generate_init_code();

        // Verify the generated code contains all regions
        assert!(init_code.contains("Region 0"));
        assert!(init_code.contains("Region 1"));
        assert!(init_code.contains("Region 2"));
        assert!(init_code.contains("0x00000000")); // Flash base
        assert!(init_code.contains("0x20000000")); // RAM base

        // Print the generated code for manual inspection
        println!("\nGenerated MPU initialization code for nRF52840:");
        println!("{}", init_code);

        // Verify all regions are valid
        for region in allocator.allocated_regions() {
            assert!(region.validate().is_ok());
        }
    }

    #[test]
    fn test_imxrt1062_has_16_regions() {
        // i.MX RT1062 (M7-class) has 16 MPU regions vs 8 on M4-class parts
        let hw_caps = HardwareCapabilities::imxrt1062();
        assert_eq!(hw_caps.mpu_regions, 16);

        let allocator = MPUAllocator::new(hw_caps);
        assert_eq!(allocator.available_regions(), 16);
    }

    #[test]
    fn test_m7_can_allocate_more_than_8_regions() {
        // Validate that the allocator actually uses all 16 regions on M7
        let mut allocator = MPUAllocator::new(HardwareCapabilities::imxrt1062());

        for i in 0u32..16 {
            let request = MPUAllocationRequest {
                memory: Memory {
                    index: i,
                    initial: 1,
                    maximum: None,
                    shared: false,
                    memory64: false,
                },
                permissions: MPUPermissions::FullRW,
                attributes: MPUAttributes::normal(),
                preferred_base: Some(0x20000000 + i * 0x10000),
            };
            allocator.allocate(request).unwrap_or_else(|e| {
                panic!("region {} allocation failed: {:?}", i, e);
            });
        }

        assert_eq!(allocator.available_regions(), 0);
        assert_eq!(allocator.allocated_regions().len(), 16);
    }

    #[test]
    fn test_m4_class_caps_at_8_regions() {
        // Negative — M4-class parts must reject the 9th region.
        let mut allocator = MPUAllocator::new(HardwareCapabilities::nrf52840());

        for i in 0u32..8 {
            let request = MPUAllocationRequest {
                memory: Memory {
                    index: i,
                    initial: 1,
                    maximum: None,
                    shared: false,
                    memory64: false,
                },
                permissions: MPUPermissions::FullRW,
                attributes: MPUAttributes::normal(),
                preferred_base: Some(0x20000000 + i * 0x10000),
            };
            allocator.allocate(request).unwrap();
        }

        // 9th region must fail
        let overflow = MPUAllocationRequest {
            memory: Memory {
                index: 8,
                initial: 1,
                maximum: None,
                shared: false,
                memory64: false,
            },
            permissions: MPUPermissions::FullRW,
            attributes: MPUAttributes::normal(),
            preferred_base: Some(0x20100000),
        };
        assert!(allocator.allocate(overflow).is_err());
    }

    #[test]
    fn test_stm32h743_has_16_regions_and_double_fpu() {
        let caps = HardwareCapabilities::stm32h743();
        assert_eq!(caps.mpu_regions, 16);
        assert!(caps.has_fpu);
        assert_eq!(caps.fpu_precision, Some(synth_core::FPUPrecision::Double));
    }
}