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Fix the ROM function table code.

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The floating point table lookup was incorrect.
This commit is contained in:
Jonathan Pallant (42 Technology) 2021-10-11 15:45:34 +01:00
parent 02cb4b8b06
commit 7a05b8f3a7
1 changed files with 40 additions and 12 deletions
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52
rp2040-hal/src/rom_data.rs
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@ -1,4 +1,12 @@
//! Functions and data from the RPI Bootrom.
//!
//! From the [RP2040 datasheet](https://datasheets.raspberrypi.org/rp2040/rp2040-datasheet.pdf), Section 2.8.2.1:
//!
//! > The Bootrom contains a number of public functions that provide useful
//! > RP2040 functionality that might be needed in the absence of any other code
//! > on the device, as well as highly optimized versions of certain key
//! > functionality that would otherwise have to take up space in most user
//! > binaries.
/// A bootrom function table code.
pub type RomFnTableCode = [u8; 2];
@ -6,15 +14,15 @@ pub type RomFnTableCode = [u8; 2];
/// This function searches for (table)
type RomTableLookupFn<T> = unsafe extern "C" fn(*const u16, u32) -> T;
/// The following addresses are described at `2.8.3. Bootrom Contents`
/// The following addresses are described at `2.8.2. Bootrom Contents`
/// Pointer to the lookup table function supplied by the rom.
const ROM_TABLE_LOOKUP_PTR: *const u16 = 0x18 as _;
const ROM_TABLE_LOOKUP_PTR: *const u16 = 0x0000_0018 as _;
/// Pointer to helper functions lookup table.
const FUNC_TABLE: *const u16 = 0x14 as _;
const FUNC_TABLE: *const u16 = 0x0000_0014 as _;
/// Pointer to the public data lookup table.
const DATA_TABLE: *const u16 = 0x16 as _;
const DATA_TABLE: *const u16 = 0x0000_0016 as _;
/// Retrive rom content from a table using a code.
fn rom_table_lookup<T>(table: *const u16, tag: RomFnTableCode) -> T {
@ -28,6 +36,12 @@ fn rom_table_lookup<T>(table: *const u16, tag: RomFnTableCode) -> T {
}
}
/// To save space, the ROM likes to store memory pointers (which are 32-bit on
/// the Cortex-M0+) using only the bottom 16-bits. The assumption is that the
/// values they point at live in the first 64 KiB of ROM, and the ROM is mapped
/// to address `0x0000_0000` and so 16-bits are always sufficient.
///
/// This functions grabs a 16-bit value from ROM and expands it out to a full 32-bit pointer.
unsafe fn rom_hword_as_ptr(rom_address: *const u16) -> *const u32 {
let ptr: u16 = *rom_address;
ptr as *const u32
@ -180,8 +194,8 @@ pub fn fplib_start() -> *const u8 {
rom_table_lookup(DATA_TABLE, *b"FS")
}
/// See Table 181 for the contents of this table.
pub fn soft_float_table() -> *const u16 {
/// See Table 180 in the RP2040 datasheet for the contents of this table.
pub fn soft_float_table() -> *const usize {
rom_table_lookup(DATA_TABLE, *b"SF")
}
@ -190,8 +204,8 @@ pub fn fplib_end() -> *const u8 {
rom_table_lookup(DATA_TABLE, *b"FE")
}
/// This entry is only present in the V2 bootrom. See Table 182 for the contents of this table.
pub fn soft_double_table() -> *const u16 {
/// This entry is only present in the V2 bootrom. See Table 182 in the RP2040 datasheet for the contents of this table.
pub fn soft_double_table() -> *const usize {
rom_table_lookup(DATA_TABLE, *b"SD")
}
@ -207,9 +221,16 @@ macro_rules! float_funcs {
$(
$(#[$outer])*
pub fn $name() -> extern "C" fn( $( $aname : $aty ),* ) -> $ret {
let table: *const *const u16 = rom_table_lookup(DATA_TABLE, *b"SF");
let table: *const usize = $crate::rom_data::soft_float_table() as *const usize;
unsafe {
core::mem::transmute_copy(&table.add($offset))
// This is the entry in the table. Our offset is given as a
// byte offset, but we want the table index (each pointer in
// the table is 4 bytes long)
let entry: *const usize = table.offset($offset / 4);
// Read the pointer from the table
let ptr: usize = core::ptr::read(entry);
// Convert the pointer we read into a function
core::mem::transmute_copy(&ptr)
}
}
)*
@ -318,9 +339,16 @@ macro_rules! double_funcs {
$(
$(#[$outer])*
pub fn $name() -> extern "C" fn( $( $aname : $aty ),* ) -> $ret {
let table: *const *const u16 = rom_table_lookup(DATA_TABLE, *b"SD");
let table: *const usize = $crate::rom_data::soft_double_table() as *const usize;
unsafe {
core::mem::transmute_copy(&table.add($offset))
// This is the entry in the table. Our offset is given as a
// byte offset, but we want the table index (each pointer in
// the table is 4 bytes long)
let entry: *const usize = table.offset($offset / 4);
// Read the pointer from the table
let ptr: usize = core::ptr::read(entry);
// Convert the pointer we read into a function
core::mem::transmute_copy(&ptr)
}
}
)*