git: 07747afd516e - main - linker: Make it easier to find the VNET section layout

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=07747afd516e710814fdc65afb0e5000d046f28f

commit 07747afd516e710814fdc65afb0e5000d046f28f
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2025-10-03 14:25:38 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2025-10-03 14:32:09 +0000

    linker: Make it easier to find the VNET section layout
    
    When trying to find the address of a VNET variable from a debugger, it
    helps to have the original address of the VNET section.  In particular,
    given the address of a vnet_entry_foo symbol, one wants to easily find
    the linker file that the symbol belongs to.
    
    In link_elf_obj.c, the section address for VNET and DPCPU sections is
    overwritten in link_elf_link_preload() and link_elf_load_file().  Add an
    "origaddr" field to store the original absolute address of the section
    base.
    
    In link_elf.c the elf_file_t already has the fields we want, but they
    were not getting filled out for the kernel itself.  Fix that too, since
    that simplifies things for debuggers and improves consistency.
    
    Reviewed by:    kib
    MFC after:      2 weeks
    Differential Revision:  https://reviews.freebsd.org/D52730
---
 sys/kern/link_elf.c     | 6 ++++++
 sys/kern/link_elf_obj.c | 8 +++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/sys/kern/link_elf.c b/sys/kern/link_elf.c
index bbebadc4c395..ebd203858b66 100644
--- a/sys/kern/link_elf.c
+++ b/sys/kern/link_elf.c
@@ -518,9 +518,15 @@ link_elf_init(void* arg)
 	(void)link_elf_link_common_finish(linker_kernel_file);
 	linker_kernel_file->flags |= LINKER_FILE_LINKED;
 	TAILQ_INIT(&set_pcpu_list);
+	ef->pcpu_start = DPCPU_START;
+	ef->pcpu_stop = DPCPU_STOP;
+	ef->pcpu_base = DPCPU_START;
 #ifdef VIMAGE
 	TAILQ_INIT(&set_vnet_list);
 	vnet_save_init((void *)VNET_START, VNET_STOP - VNET_START);
+	ef->vnet_start = VNET_START;
+	ef->vnet_stop = VNET_STOP;
+	ef->vnet_base = VNET_START;
 #endif
 }
 
diff --git a/sys/kern/link_elf_obj.c b/sys/kern/link_elf_obj.c
index 151aab96f9be..a3a53a39bfd6 100644
--- a/sys/kern/link_elf_obj.c
+++ b/sys/kern/link_elf_obj.c
@@ -70,6 +70,7 @@
 
 typedef struct {
 	void		*addr;
+	void		*origaddr; /* Used by debuggers. */
 	Elf_Off		size;
 	int		flags;	/* Section flags. */
 	int		sec;	/* Original section number. */
@@ -492,7 +493,8 @@ link_elf_link_preload(linker_class_t cls, const char *filename,
 		case SHT_FINI_ARRAY:
 			if (shdr[i].sh_addr == 0)
 				break;
-			ef->progtab[pb].addr = (void *)shdr[i].sh_addr;
+			ef->progtab[pb].addr = ef->progtab[pb].origaddr =
+			    (void *)shdr[i].sh_addr;
 			if (shdr[i].sh_type == SHT_PROGBITS)
 				ef->progtab[pb].name = "<<PROGBITS>>";
 #ifdef __amd64__
@@ -1088,6 +1090,8 @@ link_elf_load_file(linker_class_t cls, const char *filename,
 				ef->progtab[pb].name = "<<NOBITS>>";
 			if (ef->progtab[pb].name != NULL && 
 			    !strcmp(ef->progtab[pb].name, DPCPU_SETNAME)) {
+				ef->progtab[pb].origaddr =
+				    (void *)(uintptr_t)mapbase;
 				ef->progtab[pb].addr =
 				    dpcpu_alloc(shdr[i].sh_size);
 				if (ef->progtab[pb].addr == NULL) {
@@ -1101,6 +1105,8 @@ link_elf_load_file(linker_class_t cls, const char *filename,
 #ifdef VIMAGE
 			else if (ef->progtab[pb].name != NULL &&
 			    !strcmp(ef->progtab[pb].name, VNET_SETNAME)) {
+				ef->progtab[pb].origaddr =
+				    (void *)(uintptr_t)mapbase;
 				ef->progtab[pb].addr =
 				    vnet_data_alloc(shdr[i].sh_size);
 				if (ef->progtab[pb].addr == NULL) {