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hv: fixup relocation delta for symbols belong to entry section

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This is to enable relocation for code32.

- RIP relative addressing is available in x86-64 only so we manually add
  relocation delta to the target symbols to fixup code32.

- both code32 and code64 need to load GDT hence both need to fixup GDT
  pointer. This patch declares separate GDT pointer cpu_primary64_gdt_ptr
  for code64 to avoid double fixup.

- manually fixup cpu_primary64_gdt_ptr in code64, but not rely on relocate()
  to do that. Otherwise it's very confusing that symbols from same file could
  be fixed up externally by relocate() or self-relocated.

- to make it clear, define a new symbol ld_entry_end representing the end of
  the boot code that needs manually fixup, and use this symbol in relocate()
  to filter out all symbols belong to the entry sections.

Tracked-On: #4441
Reviewed-by: Fengwei Yin <fengwei.yin@intel.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
This commit is contained in:
Zide Chen
2020-03-02 18:16:50 +00:00
committed by wenlingz
parent 2aa8c9e5d4
commit 49ffe168af
5 changed files with 48 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
hypervisor/boot/include/reloc.h
View File

@@ -13,7 +13,4 @@ extern uint64_t get_hv_image_base(void);
/* external symbols that are helpful for relocation */
extern uint8_t _DYNAMIC[1];
extern uint8_t cpu_primary_start_32;
extern uint8_t cpu_primary_start_64;
#endif /* RELOCATE_H */

16
hypervisor/boot/reloc.c
View File

@@ -64,7 +64,7 @@ void relocate(void)
uint64_t rela_size = 0;
uint64_t delta, entry_size = 0;
uint64_t trampoline_end;
uint64_t primary_32_start, primary_32_end;
uint64_t primary_entry_end;
uint64_t *addr;
/* get the delta that needs to be patched */
@@ -94,8 +94,7 @@ void relocate(void)
* absolute addresses
*/
trampoline_end = (uint64_t)(&ld_trampoline_end) - delta;
primary_32_start = (uint64_t)(&cpu_primary_start_32) - delta;
primary_32_end = (uint64_t)(&cpu_primary_start_64) - delta;
primary_entry_end = (uint64_t)(&ld_entry_end) - delta;
rela_end = rela_start + rela_size;
while (rela_start < rela_end) {
@@ -104,22 +103,17 @@ void relocate(void)
addr = (uint64_t *)(delta + entry->r_offset);
/*
* we won't fixup any trampoline.S and cpu_primary.S here
* we won't fixup any symbols from trampoline.S or cpu_primary.S
* for a number of reasons:
*
* - trampoline code itself takes another relocation,
* so any entries for trampoline symbols can't be fixed up
* through .rela sections
* - In cpu_primary.S, the 32 bits code doesn't need relocation
* - Linker option "-z noreloc-overflow" could force R_X86_32
* to R_X86_64 in the relocation sections, which could make
* the fixed up code dirty. Even if relocation for 32 bits
* is needed in the future, it's recommended to do it
* explicitly in the assembly code to avoid confusion.
* the fixed up code dirty.
*/
if ((entry->r_offset > trampoline_end) &&
((entry->r_offset < primary_32_start) ||
(entry->r_offset > primary_32_end))) {
if ((entry->r_offset > trampoline_end) && (entry->r_offset > primary_entry_end)) {
*addr += delta;
}
}