git: a2e28ba79238 - main - kboot: Support reading the smbios vis sysfs

[Andrew Turner]

The branch main has been updated by andrew:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=a2e28ba79238ef5842db7e4581ed85c2fb63c317

commit a2e28ba79238ef5842db7e4581ed85c2fb63c317
Author:     Andrew Turner <and...@freebsd.org>
AuthorDate: 2025-07-25 02:07:17 +0000
Commit:     Andrew Turner <and...@freebsd.org>
CommitDate: 2025-07-30 18:35:29 +0000

    kboot: Support reading the smbios vis sysfs
    
    When reading the smbios on Linux we try to access it via /dev/mem. On
    some systems we can't do this as /dev/mem is locked down. To handle
    this try reading the sysfs file first, and if that fails fall back to
    /dev/mem.
    
    Reviewed by:    imp
    Sponsored by:   Arm Ltd
    Differential Revision:  https://reviews.freebsd.org/D51413
---
 stand/kboot/kboot/main.c | 49 ++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 43 insertions(+), 6 deletions(-)

diff --git a/stand/kboot/kboot/main.c b/stand/kboot/kboot/main.c
index a8c725a514be..4a136b42a4a1 100644
--- a/stand/kboot/kboot/main.c
+++ b/stand/kboot/kboot/main.c
@@ -229,6 +229,7 @@ static struct mapping
        uintptr_t pa;
        caddr_t va;
 } map[MAX_MAP];
+static bool smbios_mmap_file;
 static int smbios_fd;
 static int nmap;
 
@@ -238,12 +239,17 @@ caddr_t ptov(uintptr_t pa)
        uintptr_t pa2;
        struct mapping *m = map;
 
-       pa2 = rounddown(pa, PAGE);
+       if (smbios_mmap_file)
+               pa2 = rounddown(pa, PAGE);
+       else
+               pa2 = pa;
        for (int i = 0; i < nmap; i++, m++) {
                if (m->pa == pa2) {
                        return (m->va + pa - m->pa);
                }
        }
+       if (!smbios_mmap_file)
+               panic("Out of bounds smbios access");
        if (nmap == MAX_MAP)
                panic("Too many maps for smbios");
 
@@ -298,6 +304,7 @@ static void
 find_smbios(void)
 {
        char buf[40];
+       void *dmi_data;
        uintptr_t pa;
        caddr_t va;
 
@@ -306,17 +313,47 @@ find_smbios(void)
        if (pa == 0)
                return;
 
+       dmi_data = NULL;
+       smbios_fd = host_open("/sys/firmware/dmi/tables/DMI", O_RDONLY, 0);
+       if (smbios_fd >= 0) {
+               struct host_kstat sb;
+               struct mapping *m;
+
+               if (host_fstat(smbios_fd, &sb) < 0) {
+                       host_close(smbios_fd);
+                       goto try_dev_mem;
+               }
+
+               dmi_data = malloc(sb.st_size);
+               if (dmi_data == NULL) {
+                       host_close(smbios_fd);
+                       goto try_dev_mem;
+               }
+
+               host_read(smbios_fd, dmi_data, sb.st_size);
+
+               m = &map[nmap++];
+               m->pa = pa;
+               m->va = dmi_data;
+               smbios_mmap_file = false;
+       } else {
+try_dev_mem:
+               smbios_fd = host_open("/dev/mem", O_RDONLY, 0);
+               if (smbios_fd < 0) {
+                       printf("Can't open /sys/firmware/dmi/tables/DMI or "
+                           "/dev/mem to read smbios\n");
+                       return;
+               }
+               smbios_mmap_file = true;
+       }
        snprintf(buf, sizeof(buf), "%#jx", (uintmax_t)pa);
        setenv("hint.smbios.0.mem", buf, 1);
-       smbios_fd = host_open("/dev/mem", O_RDONLY, 0);
-       if (smbios_fd < 0) {
-               printf("Can't open /dev/mem to read smbios\n");
-               return;
-       }
+
        va = ptov(pa);
        printf("Start of smbios at pa %p va %p\n", (void *)pa, va);
        smbios_detect(va);
        smbios_cleanup();
+       free(dmi_data);
        host_close(smbios_fd);
 }