Quoting Stephan Gerhold (2024-03-28 02:58:56) > > FWIW: This old patch series from Stephen Boyd is closely related: > https://lore.kernel.org/linux-arm-msm/20190910160903.65694-1-swboyd@xxxxxxxxxxxx/ > > > The main use case I have is to map the command-db memory region on > > Qualcomm devices with a read-only mapping. It's already a const marked > > pointer and the API returns const pointers as well, so this series > > makes sure that even stray writes can't modify the memory. > > Stephen, what was the end result of that patch series? Mapping the > cmd-db read-only sounds cleaner than trying to be lucky with the right > set of cache flags. > I dropped it because I got busy with other stuff. Feel free to pick it back up. It looks like the part where I left off was where we had to make the API fallback to mapping the memory as writeable if read-only isn't supported on the architecture. I also wanted to return a const pointer. The other weird thing was that we passed both MEMREMAP_RO and MEMREMAP_WB to indicate what sort of fallback we want. Perhaps that can be encoded in the architecture layer so that you get the closest thing to read-only memory (i.e. any sort of write side caching is removed) and you don't have to pass a fallback mapping type. Here's my stash patch on top of the branch (from 2019!). ---8<---- From: Stephen Boyd <swboyd@xxxxxxxxxxxx> Date: Tue, 14 May 2019 13:22:01 -0700 Subject: [PATCH] stash const iounmap --- arch/arm64/include/asm/io.h | 2 +- arch/arm64/mm/ioremap.c | 9 +++++---- arch/x86/mm/ioremap.c | 2 +- drivers/firmware/google/vpd.c | 22 +++++++++++----------- drivers/soc/qcom/rmtfs_mem.c | 5 ++--- include/asm-generic/io.h | 2 +- include/linux/io.h | 2 +- include/linux/mmiotrace.h | 2 +- kernel/iomem.c | 2 +- 9 files changed, 24 insertions(+), 24 deletions(-) diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h index 245bd371e8dc..0fd4f1678300 100644 --- a/arch/arm64/include/asm/io.h +++ b/arch/arm64/include/asm/io.h @@ -178,7 +178,7 @@ extern void __memset_io(volatile void __iomem *, int, size_t); * I/O memory mapping functions. */ extern void __iomem *__ioremap(phys_addr_t phys_addr, size_t size, pgprot_t prot); -extern void __iounmap(volatile void __iomem *addr); +extern void __iounmap(const volatile void __iomem *addr); extern void __iomem *ioremap_cache(phys_addr_t phys_addr, size_t size); #define ioremap(addr, size) __ioremap((addr), (size), __pgprot(PROT_DEVICE_nGnRE)) diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c index c4c8cd4c31d4..e39fb2cb6042 100644 --- a/arch/arm64/mm/ioremap.c +++ b/arch/arm64/mm/ioremap.c @@ -80,16 +80,17 @@ void __iomem *__ioremap(phys_addr_t phys_addr, size_t size, pgprot_t prot) } EXPORT_SYMBOL(__ioremap); -void __iounmap(volatile void __iomem *io_addr) +void __iounmap(const volatile void __iomem *io_addr) { - unsigned long addr = (unsigned long)io_addr & PAGE_MASK; + const unsigned long addr = (const unsigned long)io_addr & PAGE_MASK; + const void *vaddr = (const void __force *)addr; /* * We could get an address outside vmalloc range in case * of ioremap_cache() reusing a RAM mapping. */ - if (is_vmalloc_addr((void *)addr)) - vunmap((void *)addr); + if (is_vmalloc_addr(vaddr)) + vunmap(vaddr); } EXPORT_SYMBOL(__iounmap); diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c index 0029604af8a4..e9a2910d0c63 100644 --- a/arch/x86/mm/ioremap.c +++ b/arch/x86/mm/ioremap.c @@ -392,7 +392,7 @@ EXPORT_SYMBOL(ioremap_prot); * * Caller must ensure there is only one unmapping for the same pointer. */ -void iounmap(volatile void __iomem *addr) +void iounmap(const volatile void __iomem *addr) { struct vm_struct *p, *o; diff --git a/drivers/firmware/google/vpd.c b/drivers/firmware/google/vpd.c index c0c0b4e4e281..7428f189999e 100644 --- a/drivers/firmware/google/vpd.c +++ b/drivers/firmware/google/vpd.c @@ -48,7 +48,7 @@ struct vpd_section { const char *name; char *raw_name; /* the string name_raw */ struct kobject *kobj; /* vpd/name directory */ - char *baseaddr; + const char *baseaddr; struct bin_attribute bin_attr; /* vpd/name_raw bin_attribute */ struct list_head attribs; /* key/value in vpd_attrib_info list */ }; @@ -187,19 +187,19 @@ static int vpd_section_create_attribs(struct vpd_section *sec) return 0; } -static int vpd_section_init(const char *name, struct vpd_section *sec, +static int vpd_section_init(struct device *dev, const char *name, struct vpd_section *sec, phys_addr_t physaddr, size_t size) { int err; - sec->baseaddr = memremap(physaddr, size, MEMREMAP_WB); - if (!sec->baseaddr) - return -ENOMEM; + sec->baseaddr = devm_memremap(physaddr, size, MEMREMAP_RO | MEMREMAP_WB); + if (IS_ERR(sec->baseaddr)) + return PTR_ERR(sec->baseaddr); sec->name = name; /* We want to export the raw partition with name ${name}_raw */ - sec->raw_name = kasprintf(GFP_KERNEL, "%s_raw", name); + sec->raw_name = devm_kasprintf(GFP_KERNEL, "%s_raw", name); if (!sec->raw_name) { err = -ENOMEM; goto err_memunmap; @@ -252,11 +252,12 @@ static int vpd_section_destroy(struct vpd_section *sec) return 0; } -static int vpd_sections_init(phys_addr_t physaddr) +static int vpd_sections_init(struct coreboot_device *cdev) { struct vpd_cbmem __iomem *temp; struct vpd_cbmem header; int ret = 0; + phys_addr_t physaddr = cdev->cbmem_ref.cbmem_addr; temp = memremap(physaddr, sizeof(struct vpd_cbmem), MEMREMAP_WB); if (!temp) @@ -269,7 +270,7 @@ static int vpd_sections_init(phys_addr_t physaddr) return -ENODEV; if (header.ro_size) { - ret = vpd_section_init("ro", &ro_vpd, + ret = vpd_section_init(&cdev->dev, "ro", &ro_vpd, physaddr + sizeof(struct vpd_cbmem), header.ro_size); if (ret) @@ -294,10 +295,9 @@ static int vpd_probe(struct coreboot_device *dev) int ret; vpd_kobj = kobject_create_and_add("vpd", firmware_kobj); - if (!vpd_kobj) - return -ENOMEM; + if (!vpd_kobj) return -ENOMEM; - ret = vpd_sections_init(dev->cbmem_ref.cbmem_addr); + ret = vpd_sections_init(dev); if (ret) { kobject_put(vpd_kobj); return ret; diff --git a/drivers/soc/qcom/rmtfs_mem.c b/drivers/soc/qcom/rmtfs_mem.c index 6f5e8be9689c..137e5240d916 100644 --- a/drivers/soc/qcom/rmtfs_mem.c +++ b/drivers/soc/qcom/rmtfs_mem.c @@ -212,10 +212,9 @@ static int qcom_rmtfs_mem_probe(struct platform_device *pdev) rmtfs_mem->dev.groups = qcom_rmtfs_mem_groups; rmtfs_mem->dev.release = qcom_rmtfs_mem_release_device; - rmtfs_mem->base = devm_memremap(&rmtfs_mem->dev, rmtfs_mem->addr, - rmtfs_mem->size, MEMREMAP_WC); + rmtfs_mem->base = devm_memremap_reserved_mem(&pdev->dev, + MEMREMAP_WC); if (IS_ERR(rmtfs_mem->base)) { - dev_err(&pdev->dev, "failed to remap rmtfs_mem region\n"); ret = PTR_ERR(rmtfs_mem->base); goto put_device; } diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h index 303871651f8a..d675a574eeb3 100644 --- a/include/asm-generic/io.h +++ b/include/asm-generic/io.h @@ -982,7 +982,7 @@ static inline void __iomem *__ioremap(phys_addr_t offset, size_t size, #ifndef iounmap #define iounmap iounmap -static inline void iounmap(void __iomem *addr) +static inline void iounmap(const void __iomem *addr) { } #endif diff --git a/include/linux/io.h b/include/linux/io.h index 16c7f4498869..82e6c4d6bdd3 100644 --- a/include/linux/io.h +++ b/include/linux/io.h @@ -163,7 +163,7 @@ enum { }; void *memremap(resource_size_t offset, size_t size, unsigned long flags); -void memunmap(void *addr); +void memunmap(const void *addr); /* * On x86 PAT systems we have memory tracking that keeps track of diff --git a/include/linux/mmiotrace.h b/include/linux/mmiotrace.h index 88236849894d..04607c468b73 100644 --- a/include/linux/mmiotrace.h +++ b/include/linux/mmiotrace.h @@ -47,7 +47,7 @@ extern int kmmio_handler(struct pt_regs *regs, unsigned long addr); /* Called from ioremap.c */ extern void mmiotrace_ioremap(resource_size_t offset, unsigned long size, void __iomem *addr); -extern void mmiotrace_iounmap(volatile void __iomem *addr); +extern void mmiotrace_iounmap(const volatile void __iomem *addr); /* For anyone to insert markers. Remember trailing newline. */ extern __printf(1, 2) int mmiotrace_printk(const char *fmt, ...); diff --git a/kernel/iomem.c b/kernel/iomem.c index 8d3cf74a32cb..22d0fa336360 100644 --- a/kernel/iomem.c +++ b/kernel/iomem.c @@ -130,7 +130,7 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags) } EXPORT_SYMBOL(memremap); -void memunmap(void *addr) +void memunmap(const void *addr) { if (is_vmalloc_addr(addr)) iounmap((void __iomem *) addr); base-commit: 9e98c678c2d6ae3a17cb2de55d17f69dddaa231b prerequisite-patch-id: 62119e27c0c0686e02f0cb55c296b878fb7f5e47 prerequisite-patch-id: bda32cfc1733c245ae3f141d7c27b18e4adcc628 prerequisite-patch-id: b8f8097161bd15e87d54dcfbfa67b9ca1abc7204 prerequisite-patch-id: cd374fb6e39941b8613d213b4a75909749409d63 prerequisite-patch-id: d8dbc8485a0f86353a314ab5c22fc92d8eac1cc0 prerequisite-patch-id: e539621b0eccf82aabf9891de69c30398abf76a0 prerequisite-patch-id: 59d60033b80dec940201edd5aefed22726122a37 prerequisite-patch-id: 0d16b23cec20eaab7f45ee84fd8d2950657dc72e -- https://chromeos.dev
